Serial ATA Coming 294
John Doe writes "Heatseekerz.net Has a new article dedicated to Serial ATA @ Cebit 2002. This technology will be here sooner then you think!" The article is a little thin, but I haven't heard
a lot about what looks to be a very common standard in the not so distant future.
The Real Info... (Score:5, Informative)
Re:The Real Info... (Score:5, Informative)
Cnet [com.com]
SATA and ISCSI [infoworld.com]
Intel Dev paper [intel.com]
Maxtor Whitepaper [maxtor.com]
Odds? (Score:2, Funny)
Re:Odds? (Score:2)
Chances are, Intel will have a chipset out before AMD, if only because they have a larger R&D department.
Re:Odds? (Score:2)
I checked the web page of the Serial ATA working group and since AMD, Acer Labs (ALi chipset builder), SiS and VIA Technologies are contributors to the Serial ATA standard, expect Athlon-compatible motherboards to have Serial ATA connectors by at least late this summer. They have to anyway given that we'll be starting to see Serial ATA interface hard drives and optical drives about the same time.
I would not be surprised that both nVidia and ATI will have motherboard chipsets with Serial ATA support about the same time, too.
For those of us... (Score:4, Informative)
Until now hardrives have been limited to a master and a slave on a single controller. The Serial ATA standard allows you to connect more than two in a daisy chain similar to SCSI.
Hope that clears things up, it did for me.
it also... (Score:3, Informative)
-replaces the seperate power connector and integrates it with the data cable
-standardizes the location of the data/power plugs
-allows for hotswap(partly because the location of the plugs are now standard)
It'll be interesting to see (Score:5, Funny)
Re:For those of us... (Score:2)
Alternatively, if Serial ATA is really good, does that mean SCSI will become obsolete?
Are there good technical reasons for having both? Or just marketing reasons to do with charging more for SCSI drives, and keeping ATA for the low-end?
Re:For those of us... (Score:2)
Why then hard drive makers wouldn't be able to have both high-profit and low-profit items that are basically the same, would they? (FYI there has been a serial SCSI working group for a long while, they even produced working samples of controllers, I think maybe 5 years ago!)
Or less cynically (and less realistically) SCSI has a lot of gunk in it, starting over with a new spec gives them a chance to purge it all...oh, wait, starting with the ATA spec gives us all that ATA baggage, including SCSI over ATA...
Don't forget FireWire, which does at least all the big things serial ATA does, has been around a while, and is already in the market on many Sony PCs, and all Apples for the last few years. No, on the other hand, lets forget FireWire... (yeah, I know this is at least partly Apple's fault for it's patent stance, giving a reason for not using FireWire in some places and an excuse in many more).
Re:For those of us... (Score:2)
Re:For those of us... (Score:2)
The people running the FW working group seem to disagree, at the very least they are intent on not tracking all of the future SCSI logical changes, nor are the logical changes for FireWire being funneled back into "non serial" SCSI.
Other then that I agree, FireWire does seem really a whole like like SCSI with a different transport, hot plug, and support for bandwidth and timeslice reservation...
Re:For those of us... (Score:2)
ATA and USB require a CPU to intevene and manage transfers. (Do a tranfer of data from one SCSI disk to another, then one ATA disk and another, in the same machine, and the ATA transfer will eat up CPU cycles) SCSI and FireWire do not. Intel LOVES ATA and USB, because it sells more CPUs and drives up demand for faster CPUs.
Now, since Intel pretty much owns the hardware side of the PC industry, isn't it obvious why technologies intel does not favor would fall by the wayside?
Re:For those of us... (Score:2)
With SCSI I can see some point to it, because you have potentially many disks over longer distances and you want to mix-and-match and have disks support the same features. But since ATA is for the low end anyway, why not make a really basic interface where any fancy stuff is done in software on the host machine? As long as you have DMA for transfers to/from the disk, and some way to move the disk head, that's it really. Today's machines are fast enough to do all the rest for themselves.
I realize this would create a whole nightmarish set of WinDisks... but I'm surprised the 'hard card' concept hasn't caught on again since they were first introduced on XT-type machines.
Re:For those of us... (Score:2, Informative)
This is so wrong. SATA is a point to point connection. A SATA system uses a star topology. There is no way to add more devices than there are connectors on your HBA.
This is a major difference that Serial Attached SCSI (SAS) has over SATA. SAS uses the same point to point hardware as SATA but defines expanders that allow you to replicate the point to point connection to multiple devices (or more expanders). Think of the expanders as switches. (If you think about it, it seems like SAS would have bandwidth problems with this expander technique, but it's more complicated than this and I can't get more specific at the moment.)
Re:For those of us... (Score:3, Funny)
You may begin to immortalize me now.
Re:For those of us... (Score:2, Informative)
IIRC, first generation SATA is a 1500Mb/s physical link, with a 8b/10b encoding (not so sure, look at the specs), so it would provide 1200Mb/s of effective bandwith, 150MB.
From what I've heard, SATA II would double the signaling rate, among other niceties, and there are already plans for 3rd generation signaling rate.
Re:For those of us... (Score:2)
Re:For those of us... (Score:2, Interesting)
too late, unless its way cheap (Score:3, Interesting)
I am using an external drive bay that takes FW in and converts (with a very small pcb) to 40pin ide (ata100). cost isn't much ($70) and the controller isn't either ($30).
I was able to copy an 80gig drive from native ide to a remote ide via firewire on the latest linux 2.4.18 kernel in about 3 hrs or less.
serial ide would probably JUST be ide. but serial usb2 and FW are more general purpose (video, etc).
I think serial ide is just too late in the market.
Re:too late, unless its way cheap (Score:2, Informative)
Re:too late, unless its way cheap (Score:2)
It's like 1400 pages. Holy transaction overhead.
Re:too late, unless its way cheap (Score:2)
even though the spec may be verbose, the silicon needed to support it isn't any bigger than a regular ide controller (roughly).
Re:too late, unless its way cheap (Score:2)
That is in part because a very large part of what the spec covers is stuff the hardware doesn't care about (contents of the "packets" vs. how to move them around). The FW chip on a PowerBook doesn't know how to send a "I'm not on the bus" packet out, or what to do with one when it comes in (other then what it does with all incoming packets - DMA it into memory and pull the interrupt line high so the OS can come by later and sniff at it).
The other reason it is huge is specs tend to be written huge, Internet RFCs are a marvel of brevity if you compare them to what most standards bodies produce (except the IPsec ones which are a lot closer to normal standards documents...).
Re:too late, unless its way cheap (Score:2)
I share the desire for fewer interface types, but there are different tradeoffs to make with low speed (and frequently low cost required) devices like keyboards, mice and joysticks then with high speed devices (many network connections, hard drives, DVD players, displays)...and yet another set of isosocrnous devices (or whatever the term for latency intolerant is...like sound devices).
Making one standard that does it all will make it really complex (hi USB2!) and can make it costly to implement. I don't think USB2 will suffer in small devices because of how hubs have to work you can make the cheap devices cheap and the ones that have to be expensive can be expensive...except the hubs will be more costly because they are less like the simple bus USB1.x hubs could be and more like little rate converting ethernet switches.
Making two standards (say USB1.x and FireWire) have lots of political problems, but I think would have been simpler to deal with...unfortunetly that doesn't look like it will happen. Ah well, at least I can hope that USB2 and SATA don't suck more then FireWire (and I can wonder if USB2 will cut the legs out from under SATA since it might be "enough" to take the low end of the market leaving SATA in the same place ATA left SCSI...)
Re:too late, unless its way cheap (Score:2)
I think cheap and fast is the whole idea. This is meant to replace current ATA interfaces, so that means cheap, mass produced, and designed for low-end systems (as opposed to big servers).
Re:too late, unless its way cheap (Score:2)
it applies directly to the topic at hand. my point is that while serial-ide might be faster (in theory), it seems intended to be a host->drive controller, only. whereas both usb2 and firewire are more general purpose and are already shipping and functional.
and both FW and usb2 have more bandwidth on the channel (wire) than any drive can run at, external transfer rate wise.
'interesting' or 'informative' or even 'redundant' (if you must), but CLEARLY not a troll. sheesh.
Re:too late, unless its way cheap (Score:2)
In practical terms this can result in *up to* about 500 KB (yes, big B) per second transfer speed difference in several parts of the drive's transfer curve. The most optimistic transfer speed chart I found on a quick search was the one at http://www.digit-life.com/articles/fireware/ which shows a close general match between the 1394 and IDE transfer graphs, but the Firewire graph still shows a lot of erratic activity which in real use would add up to very significant margins when transferring large amounts of data or incurring a lot of random accesses with a lot of small transfers of data. And this is the *most favorable* graph for Firewire I found; a few were less than stellar. And, bear in mind that these lags are very cumulative--transferring from one 1394-to-IDE drive to another might incur unnecessary penalties of up to 1 MBps in places. I routinely deal with multi-gigabyte transfers, and that is unacceptable since it can be avoided by using a native IDE/ATA transfer or, better yet, SCSI--and now, Serial ATA.
In addition, there's alays a danger when you translate from one protocol to another, particularly if it's needless in the first place. Haven't you known people who've b0rked data when transferring it to a Firewire HD? I have. Different enclosures=different chipsets=different drivers=different amounts of maturity, whereas the ATA standards are always--well--standardized and in common usage by the time people start buying their new drives and upgrade cards or new mobos. I've even known a friend who added a new Firewire drive to his B&W G3 Mac and managed to ruin some transferred data, and Macs are bred for Firewire. Problem was, his spiffy new VST (IIRC) external 1394 drive required 3rd-party drivers at the time, and OOPS! who knows what went wrong, but something did.
Could something go wrong with a standard ATA or Serial ATA transfer? Of course. I fell prey to IDE data corruption last year from the dreaded KT-133/SB Live!/BIOS bug. But the probability of data corruption is lessened because it's such a well-accepted standard by the time it gets into the wild, whereas Firewire drive enclosures are still the Wild West in comparison.
And the reason you can forget about native Firewire drives ever becoming mainstream is that manufacturers wouldn't want the expense--nor would consumers. It's cheaper in the long term to just invent Serial ATA than it would be to commoditize either SCSI or Firwire, with their more generalized and extensive and hence more expensive controllers for each drive. Firewire and SCSI devices have to be "smart," with a lot of decisions made in the device itself. ATA, and now Serial ATA, devices can be relatively "dumb", with most of the work being done at the main controller. The cost difference would probably add about $50 retail to the cost of each drive--Mac fanatics have been dealing with that because they overpay for everything, but PC folk wouldn't stand for it. We want big, fast, reliable--*and* inexpensive, and neither Firewire nor SCSI can really do all of that for hard drives.
Time has proven, though, that IDE/ATA/and soon (if all goes well) Serial-ATA can. Why pay %50 more per drive, when the cost of quality Maxtor/Seagate/etc. drives is getting so ridiculously low that that would add 50% to the cost of a low-end drive or 25% to the cost of a high-end drive, for no gain in HD performance? The only performance improvement would be a significant reduction in CPU usage, but that's not an issue on consumer-level and low-end workstation/server machines which are now well into the GHz+ range--and servers and high-end workstations would be running proven SCSI anyway.
Just my opinion, though. Firewire drives have their place--in Macs.
Re:too late, unless its way cheap (Score:2)
Firewire can be fast enough, depending on which version you're talking about. However, firewire is a more complicated interface with many more features than are needed by IDE drives. When Intel decided not to include Firewire in the BX chipset like was originally proposed, it lost a lot of steam. I don't know the implementation and licensing cost issues, but since it hasn't been integrated into a chipset yet, I guess they're significant enough that it's just not going to happen.
Re:too late, unless its way cheap (Score:2)
Wow, a whopping 7.4 megs per second? I wouldn't exactly call that high speed...
Re:too late, unless its way cheap (Score:2)
this was NOT a block-by-block copy. it was a recursive 'find . | cpio -pvd
Sooner than I think? (Score:3, Interesting)
No YOU have to remember!!! (Score:2)
Big business isn't the point here. The point of ATA is to be a cheap consumer product. And, if it becomes a standard, it will only take a metter of weeks for Gateway, Dell, HP, IBM, Micron, Etc, to start shipping the new drives. Then the change starts to take over the world.
Do you think manufacturers are waiting for a gun to fire so that they can start making duplicators? Design plans for this type of equipment started as soon as the standard started to take shape. I expect to be able to buy a SATA machine from stores two or three months after the standard is approved.
I see where you are coming from, but the wheels of the electronics business wait on nothing.
Re:Sooner than I think? (Score:2)
No. At least according to the docs at serialata.org, you just need a simple adapter to connect old hard drives. I mean, it's still ATA, and of course downward-compatible. I'm really thinking about waiting for the standard to establish before buying a new PC. The star topology and the thin wires (no more 40-pin wide cables that clutter your PC case) make it worth it for me. Somewhere on the serialata.org website, there is a PDF presentation of the standard, with some pics on how the cables will look. I think it's about time for a standard like that.
Re:Sooner than I think? (Score:2)
Serial IDE drives will require a new interface logic and hardware. However, this has been comming for a long time. I doubt it's going to be a long delay before hard drive manufacturers can roll out drives with this interface.
Re:Sooner than I think? (Score:2)
Not ANOTHER standard (Score:4, Insightful)
Firewire is so cool, they should just use it for hard drives also.
Integrate the controller on the motherboard if you have to.
Re:Not ANOTHER standard (Score:2)
I'd like to see some drive that really puts out 66.6 MBytes/sec at ATA/66.
With scsi that's altogether another question. It beats shit out of ATA/66.
There's no point comparing theoretical outputs.
Re:Yuo = ignoramus (Score:2)
Is that too easy or what?
No new drivers to install, it looks to the computer just like any other standard ATA interface.
Re:Not ANOTHER standard (Score:2)
Re:Not ANOTHER standard (Score:2)
And Firewire supports up to 64 devices, daisy-chained, even on the day it was introduced: USB did not.
USB is still limited by being CPU-centric, while 1394 can move data without connection to a CPU.
Re:Not ANOTHER standard (Score:2)
HD's are pretty cheap, lets jack the pricing up by building gig ethernet into them all!
The is no royalty fee on 1394 (Score:3, Informative)
So there is not a price problem caused by Apple.
It's expensive because it's expensive. Because Intel invented USB, and Apple invented 1394, Intel has doggedly refused, even up to the present day, to support the standard on its own mobos. Intel FUD took care of the rest. So it has taken years to reduce the price of the chipsets -- but not because of the licensing fees. It's a matter of unit cost. Since Intel was actively hostile to the (superior) tech, it retarded the acceptance of 1394 and kept production costs artificially high. Chicken and egg...
But thanks to Apple, and common sense, people realized that Firewire was simply superior to USB in every way but price. Just compare an iPod to a standard USB MP3 player - transfer speed enormously faster, and Firewire also charges the iPod's batteries during the process.
So the prices came down despite determined opposition -- the market actually worked, sort of.
Firewired external CD-RW drives and hard drives work fine, and speedily. Putting the drive into the PC itself seems obvious.
The fly in this soup: 1394 developers seem determined to insert copy control into the cable/controller hardware. If there will be a choice between mediocre USB with no DRM, and 1394 with DRM, I'd throw the 1394/DRM equipment into the garbage, even if it were free!
Already /.ed! (Score:3, Funny)
FAQ from the SerialATA.org website (Score:5, Informative)
A1: Serial ATA is an evolutionary replacement for the Parallel ATA physical storage
interface. Serial ATA is scalable and will allow future enhancements to the computing
platform.
Q2: Previous efforts to transition to a serial bus were not successful. Why do you
believe that Serial ATA will be successful?
A2: Serial ATA is a drop-in solution in that it is compatible with today's software, which
will run on the new architecture without modifacation. It will provide for systems which
are easier to design, with cables that are simple to route and install, smaller cable
connectors, improve silicon design, and lower voltages which alleviate current design
requirements in Parallel ATA.
Q3: Will there still be a parallel ATA bus when Serial ATA comes out?
A3: Serial ATA's adoption by the industry will follow a phased transition path. There
will be a point where both Parallel and Serial ATA capabilities are available.
Q4: You stated that PCs implementing Serial ATA will be in the marketplace in
2002. Why does it take so long to implement?
A4: The goal of the working group is to ensure the Serial ATA transition happens as
smoothly and quickly as possible. The Serial ATA specification is expected to be
complete in the fall of 2000 with adoption to happen in the following 12 to 18 months.
Q5: What are the end user benefit of Serial ATA?
A5: End users will benefit by being able to easily upgrade their storage devices.
Configuration of Serial ATA devices will be much simpler, with many of today's
requirements on jumper and settings no longer needed.
Q6: What is the cost to implement Serial ATA in a system?
A6: The cost of Serial ATA technology will be on par with today's Parallel ATA
technology.
Q7: Who are the members of the Serial ATA Working Group? Can new companies
join?
A7: The Serial ATA promoters group includes APT Technologies Inc, Dell Computer
Corporation, International Business Machines, Intel Corporation, Maxtor Corporation,
Quantum Corporation, and Seagate Technology. Information on joining the working
group is available at www.serialata.org and new members are welcome.
Q8: Hard disk data rates don't seem to be pushing the limits of current ATA66
technology. Why is Serial ATA being planned now?
A8: Serial ATA is an evolutionary replacement for the Parallel ATA physical storage
interface and will allow future enhancements to the computing platform. Specifically, the
thinner Serial ATA cable addresses OEM's concerns regarding airflow around the
Parallel ATA cable, and enables design of smaller PC chassis, as well as silicon vendors
concerns regarding 5 volt tolerance support in future designs.
Q9: Will Serial ATA be compatible with today's PCs?
A9: Serial ATA electronics and connectors will differ from Parallel ATA, however the
technology is software compatible and OS transparent. It is anticipated that there will be
adapters to facilitate forward- and backward-compatibility of hard disks on PC systems.
Q10: What is the impact of Serial ATA on OEMs?
A10: Industry benefits of Serial ATA include systems which are easier to design with
cables that are simple to route and install, smaller cable connectors with improved silicon
design, lower voltage which alleviates current design requirements in Parallel ATA and
compatibility with today's software which will run on the new architecture without
modification.
Q11: Beyond hard disks, will Serial ATA be used on floppy drives, optical drives,
DVDs, and ZIP drives?
A11: Serial ATA supports all ATA and ATAPI devices, including CDs, DVDs, tapes
devices, high capacity removeable devices, zip drives, and CDRW's.
Q12: What is the impact of Serial ATA on IEEE1394 (aka Firewire) and on USB2
in terms of PC system function?
A12: Serial ATA is planned to be the primary storage interface inside the PC system,
and is not planned as an external interface to PC storage or peripherals. USB2 and
IEEE1394 connections on the PC can be used where required as peripheral interfaces.
Q13: When does Microsoft plan to support Serial ATA in its OS's?
A13: Serial ATA is software compatible with Parallel ATA and requires no changes to
Microsoft operating systems, or any other OS as well.
Q14: What are the licensing requirements and costs of Serial ATA to companies
that want to use the technology?
A14: When the Serial ATA specification is complete, it will be made available at no
charge. The working group expects to complete the specification later this year.
Re:FAQ from the SerialATA.org website (Score:5, Interesting)
Questions not answered by the FAQ:
Re:FAQ from the SerialATA.org website (Score:2)
Re:FAQ from the SerialATA.org website (Score:2)
One meter cable length doesn't work real well for external devices, and for external devices you want to be able to hot plug the device like you can with Firewire or USB. Those interfaces are better designed for most external storage devices. It is a lot easier to design an interface that doesn't have to worry about drives disappearing and reappearing.
Will I still be able to use a serial ATA device 10 years from now? I can (and do) use 10 year old SCSI devices. Will the SerialATA consortium guarantee backward compatibility, or is this yet another lock in to a perpetual upgrade cycle?
I'm not sure how the people writing the standards can guarantee forward compatibility. You're asking them to say it will work with something that hasn't been invented yet. A more reasonable comparison is to ask if old ATA dirves will work with SerialATA, and they will with an adapter card.
Re:FAQ from the SerialATA.org website (Score:2)
and now for something that's not slashdotted.. (Score:2, Informative)
SerialATA doesn't seem very advanced (Score:3, Interesting)
1) Power to the device is still separated from the data connection.
2) Because it is backwards compatible with regular ATA it appears it will have the same limitations on the number of devices you can connect, i.e. 2 per channel.
3) It is unusable for external devices.
Why upgrade to a standard whose only advantage is a speed increase we don't need and smaller cables that can be done with parallel ATA ala "round" IDE cables? Seems like a huge investment that would be better made in FireWire 2.0 or something similar so that you can use the same interface internally and externally, with power provided, and have many devices on the same bus.
Re:SerialATA doesn't seem very advanced (Score:5, Insightful)
For 1), I have heard that, indeed, power and data are together in a single connection, or at least it is tandardized to make hotswap feasible.
2) This is completely false, one of the main points of *serial* ATA was to increase the chain lengths to SCSI level capacities. The focus is on software compatibility, not transparent hardware compatibility. They say in the beginning, they expect motherboards that have Serial ATA to also have Parallel ATA on the same motherboard...
3) Why is it not usable for external devices? For one, they have extended cable length to three feet between points on the chain. No where near SCSI capability, but three feet from an interface card isn't bad. I suspect you could at the very least have SCSI solutions in ATA with this.
You are right that FireWire or USB2 might be worth a second look, but at the current rate, no one wants to bother scrapping everything they have based on ATA to pursue such a dream. I would much rather have Serial ATA than our current ATA. Of course, I have to wonder if the industry will even see this move as worth it. Even if from a software perspective it behaves similarly to ATA, I would think the hardware implementers have been holdig back. ATA is seen to meet the demands of home users, and SCSI supplies advanced features to businesses that need it. Hardware vendors have a vested interest in maintaining that dicotomy, since they can charge a huge premium for SCSI without problems coming up in the Desktop market...
Re:SerialATA doesn't seem very advanced (Score:2)
Re:SerialATA doesn't seem very advanced (Score:2, Insightful)
2. This is incorrect, the signalling is shorter, and sATA does not want to compete with SCSI, in the future, SCSI and sATA will use the same interconnect and you choose based on how much money you want to spend. SCSI runs 25 meters point to point while sATA is 1m.
3. Nope, the distance is still 1m. No extra length. It is possible to change the spec a bit and give distance, but what would you run it to. Since it is point-to-point, and the software stacks can't handle more than two devices on a bus, what would you connect but one drive, or possibly two with a special chip?
SCSI is offering a compatible solution at http://www.serialattachedscsi.com
Re:SerialATA doesn't seem very advanced (Score:2)
Re:SerialATA doesn't seem very advanced (Score:3, Informative)
However the Maxtor presentation [serialata.org] talks about using SATA as a replacement for SCSI, or at a minimum breaking into NAS and low end servers.
Cable length is up to 3M from the Intel presentation [intel.com].
Also for the number of devices, since it's now PTP connections, it's relatively agnostic as to the number of devices since it no longer fits into the old model of channels. I still haven't found specific references for the number of devices, but the Maxtor presentation has a picture of a SATA drop-in PCI card with 6 SATA connectors.
Re:SerialATA doesn't seem very advanced (Score:2)
But...how is a 6 drive SATA controller 100% software compatible with a older ATA spec that supported exactly two drives? Does the one SATA controller show up as 3 (or six) "normal" ATA controllers? Or is 100% really 100% except when you have more then two devices, send more then X bps, it is a day ending in Y, or the pope is waring a funny hat?
And isn't it sad that "requires no changes to Windows" has started being a major hardware feature?
Re:SerialATA doesn't seem very advanced (Score:2)
And yes it is sad.
Re:SerialATA doesn't seem very advanced (Score:2)
Since when have PC manufacturers followed what Apple has done, other than cosmeticly. There are also royalties to be paid on Firewire, but not on Serial ATA. Of course since Apple is one of the developers of Firewire, they're paying most of that royalty to themselves. If i remember correctly it was a pretty small royalty though, maybe a little under $1 a device, might even be less.
Personaly, I'd rather see SCSI drives than a new version of ATA.
If you want the benefits of SCSI, you're welcome to pay the extra that it costs. Most people won't notice any difference in their system from going from IDE to SCSI, why should they pay for SCSI.
Re:SerialATA doesn't seem very advanced (Score:5, Informative)
> 1) Power to the device is still separated from the data connection.
This is because the motors being currently used in hard drives pull a few amps at spinup time, and the wire guage used for signalling cannot possibly carry this much current. There is a thought that once the market is serial ATA native, the HD manufacturers will then standardize on a 5V, low current motor instead of the current 12V beasts, however, things like Microsoft's "on now" spec and other crap specify a minimum spinup time that force us to slam the motor to get up to speed.
Single connector vs two connectors has little bearing on whether you can hot swap. It is a function of how you isolate/protect your power circuitry from not having all the conductors touching at the same time. (e.g., in current ATA, what happens when of the +12,0,+5,-5, only the +12 and the -5 are connected because the pins are slightly out of tolerance?)
> 2) Because it is backwards compatible with
> regular ATA it appears it will have the same
> limitations on the number of devices you can
> connect, i.e. 2 per channel.
It is point to point. The notion of channels will disappear, and BIOSs in the future will simply allocate an 8-word I/O space address for the device, instead of todays "primary IDE" at 0x1F0 or whatever.
> 3) It is unusable for external devices
I don't believe that is correct, however, since it is point to point, a box of external drives (similar to a SCSI enclosure) would need a cable running to it for every drive in the enclosure.
There will be no daisy chaining or hub or star network of SATA devices.
Bundling the cable (Score:2)
I suppose there will be fewer lines than parallel ATA because serial ATA is, well, serial. Also, instead of the standard flat ATA cable with its parallel wires just made for crosstalk and interference, they could use a balanced twisted pair for greater noise immunity. Because the the wires in the pair are twisted and the signal is taken as the difference between the two wires, any stray EM tends to affect both wires equally and thus cancel itself out. Also radiation from the pair is reduced because balanced current running in opposite directions tends to cancel out its own raditions.
CPRM on ATA? (Score:4, Informative)
oh joy, yet another "standard" (Score:2, Insightful)
to compete with the firewire (and upcoming gigawire) "standard" and the usb 1.x and 2.x "standards". oh and we have ata/133/100/66 "standards". scsi 1/2/3/4/5/ultra/wide/thin/mega-super-fun "standards" too.
how come none of my "standard" devices talk to each other very well?
well three cheers for the latest "standard". by the time it's on everyone's hardware it will be superceeded a dozen times or so.
Re:oh joy, yet another "standard" (Score:2)
>gigawire) "standard" and the usb 1.x and 2.x
>"standards". oh and we have ata/133/100/66
>"standards". scsi
>1/2/3/4/5/ultra/wide/thin/mega-super-fun
>"standards" too.
>
>how come none of my "standard" devices talk to
>each other very well?
How do SCSI devices not talk to one another well? I've run SCSI-1 devices on Ultra2 controllers and vice versa without a single glich. Likewise, I've run ATA/33 devices on ATA/100 controllers and vice versa without a single glich.
I have little experience with either USB or Firewire, but I've never heard of problems with backwords compatibility on either of them.
Matt
Seems /.ed... Here's the article: (Score:5, Informative)
Serial ATA, A New Standard
Serial Advanced Technology A ttachment is an evolutionary high-speed serial link replacement for the parallel ATA attachment of internal storage devices. It connects hard disks, DVDs, CD-R/Ws, zip drives and all other ATA and ATAPI devices to the motherboard in desktop and mobile PCs, servers and network storage.
The new point-to-point device communicates trough a 4 layer interface:
4) Application Layer 3) Transport Layer 2) Link Layer 1) Physical Layer
If you want more information, you can download the Serial ATA 1.0 specifications at http://www.serialata.org
The reason for the late breakthrough of Serial ATA is that nobody wanted to, unnecessarily, spend time and money, developing a new interface. Because of the higher performance demands, several companies had to cooperate developing a much better, more intelligent ATA: Serial ATA will allow these future enhancements to the computing platform.
The Serial ATA working group that developed the Serial ATA specification was led by APT Technologies Inc, Dell Computer Corporation, International Business Machines (IBM), Intel Corporation, Maxtor Corporation, and Seagate Technology.
Seagate and Maxtor told us the new drives would be shipping in autumn, but the real breakthrough will take place when chipset manufacturers (Intel/Via) have integrated Serial ATA on their Southbridge.
Benefits
Let's take a look at some end user benefits of Serial ATA:
No software depency, it's 100% compatible with today's software and OS transparent.
Easier configuration of the storage devices (jumpers are no longer needed).
Supports lower cost device architectures.
Much better cabling and connectors: the thin and flexible cables result in better airflow trough the pc housing and enables design of smaller PC/motherboard chassis. Therefore, they are simple to route and install, and can be up to 1m long.
Last but not least, a higher bandwidth: the transfer rate exceeds all current ATA standards. Generation 1, 2 and 3 S-ATA supports respectively up to 150MB/s (1.2Gbits/sec), 300MB/s (2.4Gbits/sec), 600MB/s (4.8Gbits/sec). As Serial ATA works asynchronous, there are no isochronous requirements.
The Prototypes
Seagate's SATA prototype:
Maxtor's prototype:
When we take a closer look at the connectors, we see there's a slight difference: Maxtor used the 35B1 configuration, starting right: the Serial ATA connector, with both power and signal segments, legacy jumper and power connector. Seagate used the 35B4 configuration which has no legacy power connector.
The Serial ATA signal segment counts seven pins: three ground pins a transmitter signal pair and a receiver signal pair. The Serial ATA power segment counts 15 pins, containing three different voltages: 3.3V, 5V and 12V.
The prototypes momentary shown, need a PCI-to-SATA host controller or a SATA-to-Parallel ATA bridge chip.
Maxtor used the first one:
The Future
By the end of 2002, there should be SATA-sytems on the market. As you might have noticed, the parallel ATA is finally dead, though it could take up to four years to eliminata all parallel ATA devices. Nevertheless, I'm going to wait buying a new system, because most new technology suffers childhood disease.
The FAQ (Score:2, Redundant)
Q1:What is Serial ATA and Why is it being developed?
A1: Serial ATA is an evolutionary replacement for the Parallel ATA physical storage interface. Serial ATA is scalable and will allow future enhancements to the computingplatform.
Q2: Previous efforts to transition to a serial bus were not successful. Why do you believe that Serial ATA will be successful?
A2: Serial ATA is a drop-in solution in that it is compatible with today's software, which will run on the new architecture without modifacation. It will provide for systems which are easier to design, with cables that are simple to route and install, smaller cable connectors, improve silicon design, and lower voltages which alleviate current design requirements in Parallel ATA.
Q3: Will there still be a parallel ATA bus when Serial ATA comes out?
A3: Serial ATA's adoption by the industry will follow a phased transition path. Therewill be a point where both Parallel and Serial ATA capabilities are available.
Q4: You stated that PCs implementing Serial ATA will be in the marketplace in2002. Why does it take so long to implement?
A4: The goal of the working group is to ensure the Serial ATA transition happens as smoothly and quickly as possible. The Serial ATA specification is expected to becomplete in the fall of 2000 with adoption to happen in the following 12 to 18 months.
Q5: What are the end user benefit of Serial ATA?
A5: End users will benefit by being able to easily upgrade their storage devices. Configuration of Serial ATA devices will be much simpler, with many of today's requirements on jumper and settings no longer needed.
Q6: What is the cost to implement Serial ATA in a system?
A6: The cost of Serial ATA technology will be on par with today's Parallel ATAtechnology.
Q7: Who are the members of the Serial ATA Working Group? Can new companies join?
A7: The Serial ATA promoters group includes APT Technologies Inc, Dell Computer Corporation, International Business Machines, Intel Corporation, Maxtor Corporation, Quantum Corporation, and Seagate Technology. Information on joining the working group is available at www.serialata.org and new members are welcome.
Q8: Hard disk data rates don't seem to be pushing the limits of current ATA66technology. Why is Serial ATA being planned now?
A8: Serial ATA is an evolutionary replacement for the Parallel ATA physical storageinterface and will allow future enhancements to the computing platform. Specifically, thethinner Serial ATA cable addresses OEM's concerns regarding airflow around the Parallel ATA cable, and enables design of smaller PC chassis, as well as silicon vendors concerns regarding 5 volt tolerance support in future designs.
Q9: Will Serial ATA be compatible with today'sPCs?
A9:Serial ATA electronics and connectors will differ from Parallel ATA, however the technology is software compatible and OS transparent. It is anticipated that there will be adapters to facilitate forward- and backward-compatibility of hard disks on PC systems.
Q10: What is the impact of Serial ATA on OEMs?
A10: Industry benefits of Serial ATA include systems which are easier to design withcables that are simple to route and install, smaller cable connectors with improved silicondesign, lower voltage which alleviates current design requirements in Parallel ATA and compatibility with today's software which will run on the new architecture withoutmodification.
Q11: Beyond hard disks, will Serial ATA be used on floppy drives, optical drives,DVDs, and ZIP drives?
A11: Serial ATA supports all ATA and ATAPI devices, including CDs, DVDs, tapesdevices, high capacity removeable devices, zip drives, and CDRW's.
Q12: What is the impact of Serial ATA on IEEE1394 (aka Firewire) and on USB2in terms of PC system function?
A12: Serial ATA is planned to be the primary storage interface inside the PC system, and is not planned as an external interface to PC storage or peripherals. USB2 and IEEE1394 connections on the PC can be used where required as peripheral interfaces.
Q13: When does Microsoft plan to support Serial ATA in its OS's?
A13: Serial ATA is software compatible with Parallel ATA and requires no changes toMicrosoft operating systems, or any other OS as well.
Q14: What are the licensing requirements and costs of Serial ATA to companiesthat want to use the technology?
A14: When the Serial ATA specification is complete, it will be made available at nocharge. The working group expects to complete the specification later this year.
FireWire is already on the ball. (Score:2, Insightful)
Re:FireWire is already on the ball. (Score:2)
Firewire could support up to 63 internal hard drives, although they would each have to share the same bus. SerialATA allows for chaining of drives, but doesn't mention how many can be chained. I imagine that motherboards will have 2 SerialATA channels late this year, and 4 at some point next year - allowing SATA RAID 5 (3+1 drives) at a combined throughput of 600MBps...
But SerialATA has one major advantage. To the OS, is looks like a standard ATA interface - no driver changes are required at all. This isn't the case with Firewire currently. Hence it will succeed in my opinion (as well as being on every motherboard come 2003).
Re:FireWire is already on the ball. (Score:2)
>for FireWire [apple.com],
It's 600MB, not 600Mb, and that's in a future revision. The initial devices will be 150MB vs 400Mb on firewire, or about three times faster than firewire.
Matt
Serial ATA could REALLY cut into SCSI sales (Score:2, Flamebait)
First, Serial ATA will offer a major leap up in terms of transfer speeds. The initial speeds will be equivalent of ATA-150, but we will eventually see the equivalent of ATA-300 and ATA-600 speeds, which far surpasses even the current Ultra-Wide SCSI 160 standard. I'm sure companies like Promise are working on RAID controllers for Serial ATA that will allow an even bigger leap up in hard disk performance.
Second, because Serial ATA has finally dispensed with using a ribbon cable, this means way less clutter inside the computer and could also mean system cases can be designed for more efficient air cooling.
Third, Serial ATA--unlike SCSI--doesn't require you to load device drivers out of the wazoo to support devices on the bus. The only driver you'll probably need is the driver for the motherboard chipset that incorporates Serial ATA support.
I mean, let's face it--SCSI is still pretty expensive due to the cost of host adapters, cabling and SCSI peripherals. SCSI is only really useful where lots of SCSI device access (for example, hard disks) is required, primarily in server environments. For workstation and home computer use, Serial ATA offer most of the high-speed disk access of SCSI, but at a much lower cost.
In short, SCSI will become increasingly a niche product. And SCSI may eventually get competition from the high end of mass storage interfaces as the cost of Fibre Channel devices drops.
Re:Serial ATA could REALLY cut into SCSI sales (Score:3, Interesting)
Re:Serial ATA could REALLY cut into SCSI sales (Score:2, Informative)
Linux isn't supperior in this, if anything, given the initrd method and the way in which ordering of driver loading is specific and the bugs in RH 7.2s installer, the MS method of signing drives and not changing their names depending upon the loading of SCSI drivers gives MS a bit of an edge in this storage model.
Re:Serial ATA could REALLY cut into SCSI sales (Score:2)
Er, that is exactly how MacOS X does it, and I think how Mac OS prior to OSX also did it.
Re:Serial ATA could REALLY cut into SCSI sales (Score:2, Insightful)
Many of us simply can't live with the four-device limitation. SCSI and Fiber Channel shine when scalability is needed. There are many applications for multi-controller multi-drive RAID devices that ATA simply isn't cut out for. It is also nice to just be able to add another device when needed--SCSI is very convenient.
This is comparing something that doesn't exist to something that does. Also, Ultra320 SCSI [scsita.org] is just around the corner.
Third, Serial ATA--unlike SCSI--doesn't require you to load device drivers out of the wazoo to support devices on the bus.
This is untrue. One SCSI driver allows me to connect any SCSI device: hard disks, ZIP drives, scanners, etc. The only additional drivers are those needed for non-SCSI devices, such as the parallel port or a modem.
Not in the long-term. Good system administrators are more expensive than SCSI controllers, and the time and frustration saved more than pays for the SCSI controllers.
And in the home, SCSI really never had a foot-hold, so Serial ATA changes nothing.
In short, ATA never really competed with SCSI and never will. As long as ATA is crippled to be useful only in personal computers, it will never appear in big computers, multi-user computers, or high-performance workstations. These are not niche markets, either.
Re:Serial ATA could REALLY cut into SCSI sales (Score:2)
The only reason SCSI is really expensive is because Joe Consumer hasn't adopted it. If the industry went with SCSI then SCSI vendors could lower their prices. Of course, that won't happen until vendors lower their prices, a catch 22 really.
Also, I really doubt serial ATA would bite into the server market. SCSI has such a robust history (once you get it terminated correctly!), admins like to go with what they know works. Plus scsi supports tagged command queueing, which has yet to be implemented to any reasonable degree on the ATA side.
Re:Serial ATA could REALLY cut into SCSI sales (Score:2)
Because today's bus-mastering SCSI host adapters off-load storage device access to minimize CPU cycle usage, this already means very fast access to any storage device connected to the SCSI bus. That's why SCSI is very popular for servers, where fast access to the hard drive is a must.
However, for standalone computer users, SCSI is way overkill except in a very few cases (for example, multimedia authoring). The majority of computer users don't really stand to benefit from bus-mastered SCSI, alas....
Re:Serial ATA could REALLY cut into SCSI sales (Score:2)
Just the switch to thin cables will definitely help the system case cooling issue.
Three paragraphs per page??? (Score:4, Interesting)
As far as the name "Serial ATA," it's a smart move. It will create the impression in people's mind that it's an "extention" or "enhancement" of standard ATA, without necessarily being backwards compatible at all. But, hey, once it gains market share, and the SATA drives start filling the shelves at Best Buy, it won't really matter.
Re:Three paragraphs per page??? (Score:2)
Serial ATA Nodes.
I do wonder what would be involved in cable extender devices (relays? repeaters? hubs? whatever...).
Built-in is often nice, but especially if it's hot swappable, external drives are often quite useful. E.g., if they're cheap enough you could plug in a disk for a back-up, then remove it and put it on the shelf until it was time for it to go off-site.
Now I'll grant that one can do that with drives built into the chasis, but unless they start puttin more slots in a tower that's not a practical answer. (Currently we use an external tape drive, but as disk sizes increase it takes longer and longer to do the backup. And as disk prices drop, the price of the inconvenience of using tapes becomes less justifiable. So an external disk drive seems headed towards the right answer.)
.
Its coming. (Score:2)
The Benefits of Serial ATA (Score:4, Informative)
Performance - doesn't anyone care? (Score:2)
For REAL performance, give me SCSI (or fiber channel) any day. Here's why: The serial I/O technologies for the PC, as well as the abomination called IDE, utilize CPU interrupts and the system bus to move data. The devices cannot "talk" to each other without utilizing CPU power.
For me, this is a major problem. I installed an IDE drive last weekend (because they're cheap) and while I was copying files (some 15 GB worth), my CPU usage was near 90%. All other processes were slowed down, so much so that I couldn't compile, render, play games or even edit code or browse http comfortably while this was happening.
On the other hand, when I copy files or burn CDs from one SCSI device to another, my CPU goes unmolested while these fine (Ultra320 LVD) devices talk (scream, rather) to eachother at lightning speeds.
Why bother creating new serial architectures that are no better than what we already have? Why not work at getting a SCSI drive down to the same price as an IDE drive.. or ( GASP! ) change the sorry PC architecture to have more than 16 IRQs! This would make me slightly less averse to burning up my scarce IRQs on IDE controllers.
To summarize - you lose system performance when using CPU intensive I/O. So avoid it if you like to use your computer and your storage devices at the same time... and if you can afford it.
Vortran out
Re:Performance - doesn't anyone care? (Score:2)
If anyone is curious about getting into the world of SCSI, here's what I suggest:
You can get refurbished Plextor optical drives at many online stores. I use www.hypermicro.com [hypermicro.com] the most. They have great products and service. I've bought almost all of my SCSI peripherals from them.
I bought an Asus P2L97-DS motherboard (dual processor, slot 1, PII 266-333 and Celeron 266 to 533, 0 - 512MB PC66 to PC133 RAM, 4 DIMM slots, integrated Ultra Wide SCSI, 4PCI/3ISA, 2x AGP) on ebay for about $50. This is a great intro board to both SMP and SCSI. All you need is two cheap Celeron processors and you're all set.
If you want to use refurbished hard drives, I suggest searching ebay for someone who's got lots of positive feedback and a non-DOA warranty. You can get 9GB and 18GB Ultra 160 hard drives incredibly cheap, due to the cut-throat competition.
Tekram makes inexpensive, powerful SCSI host adapters. They use the LSI Logic chipset, which is extremely well supported under Linux. Adaptec SCSI host adapters are lot more expensive, but you can find them much easier at retail stores.
If you wanted to, you could get a dual processor Asus motherboard, Plexter SCSI CDROM, Plextor SCSI CDRW, and a 4.55GB Ultra Wide SCSI hard drive for something like $250. Then, grab two Celeron or Pentium II processors off ebay (about $25-$50 each), an Enlight 7237 case ($50-$75, depending on the power supply), and a Matrox G200 or other cheap, well supported AGP card. In the end, I doubt it would even come close to $500. And now you have your very own SMP SCSI workstation.
Re:Performance - doesn't anyone care? (Score:2)
In any case, the ATA/SCSI thing is true, ATA does use CPU, and SCSI doesn't (as much). And this is the reason why Intel promotes ATA and not SCSI, and why computer manufacturers include ATA controllers by default, and not SCSI. Because SCSI does not drive demand for more/faster Intel CPUs.
Re:Performance - doesn't anyone care? (Score:2)
SCSI devices can talk to each other, not just to a "SCSI CPU Device". The very very seldom do. When someone added the experimental splice system call to Ultrix (or was it DIGITAL Unix at the time? or maybe NetBSD/Alpha) they did support SCSI disk to tape and disk to disk copies. As far as I know that was the first and last time it was done in any "common" OS.
That is true, what the splice code did was on the read side look at the block numbers in the inode, and the first and second (and third if that FFS used it) level indirect block tables. On the write side to a tape device it was trivial, for another disk device it had to use the normal FFS code to find space for new blocks, which caused a normal read of the free block map, and normal writes to the block map and the block (indirect) tables for the inode (and the cache for the block to be written had to be invalidated). However in both cases the data writes went from device to device without going through main memory.
The speed up from skipping the CPU/memory step was modest. The speed up from being able to do the reads and writes somewhat out of order was less modest. The speed up or slowdown from not getting the recently written blocks in the block cache was frequently larger then the other effects.
As it turned out the larger win for splice was in dealing with network I/O and skipping the user-to-user context switches, which may be why neither Linux nor the BSD's implement their splice-like calls (sendfile I think) in a way that skips the CPU, they just avoid user-to-user context switches.
If the experiment was re-done it might be different, the memory wall keeps getting larger, and modern CPUs throw away a lot more pending work then the old Alpha did.
All this stuff was written up in one of the mid-90's Usenix reports if you want to read it in more detail then I remember.
Adaptec's Serial ATA controller (Score:2, Insightful)
This is one new standard I'm willing to accept. In fact, I'm a bit surprised by the number of people here scoffing at Serial ATA. With performance of some parallel ATA drives matching mainstream SCSI drives for months now, with capacities closing in, and with SCSI manufacturers continuing to slowly drop production of SCSI optical drives, I think the end of SCSI is near. I never thought I'd say that, but I really think it is.
So to all you people saying that this just introduces a new standard to a "mess", I think you're wrong. This will end the division between desktop storage and mid-level server storage. Firewire and USB will stick around - but only as the external storage interface options they should be.
Serial SCSI replacement? (Score:3, Interesting)
Still has 137GB Limitation (Score:2, Insightful)
I'm surprised that the opportunity was missed to address this with the introduction of Serial ATA.
For the curious, the limit comes about since only 28bits are used for the sector number in the ATA protocol. (2^28 * 512 bytes = 137.4Gb).
This is straying dangerously off topic now, but its quite amusing to look at the history of arbitrary hard disk size limits: (from The Storage Review [storagereview.com])
PC/XT Parameter (10.4 MiB / 10.9 MB) Barrier
FAT12 Partition Size (16 MiB / 16.7 MB) Barrier
DOS 3 (32 MiB / 33.6 MB) Barrier
The 1,024 Cylinder (504 MiB / 528 MB) Barrier
The 4,096 Cylinder (1.97 GiB / 2.11 GB) Barrier
The FAT16 Partition Size (2.00 GiB / 2.15 GB) Barrier
The 6,322 Cylinder (3.04 GiB / 3.26 GB) Barrier
The Phoenix BIOS 4.03 / 4.04 Bug (3.05 GiB / 3.28 GB) Barrier
The 8,192 Cylinder (3.94 GiB / 4.22 GB) Barrier
The 240 Head Int 13 Interface (7.38 GiB / 7.93 GB) Barrier
The Int 13 Interface (7.88 GiB / 8.46 GB) Barrier
The Windows 95 Limit (29.8 GiB / 32.0 GB) Barrier
The 65,536 Cylinder (31.5 GiB / 33.8 GB) Barrier
The ATA Interface Limit (128 GiB / 137 GB) Barrier
And only four of them are due to Microsoft...
Re:Still has 137GB Limitation (Score:4, Insightful)
Most vendors don't need to support 48-bits yet because they don't have drives that are big enough. Many manufacturers do not make 4-platter IDE drives anymore, and with the current technology of 40GB/platter, the 3-platter disks are only 120GB.
When the next generation comes in at 60 or 80 GB/platter, they'll support 48-bit commands as needed.
Serial ATA won't replace SCSI (Score:2, Informative)
And Ultra320 is on the horizon already. And by the time Serial ATA reaches 600MB/sec I'd expect SCSI to have continued to grow.
Just because you can put two cows side by side doesn't make them an ox team.
Number of Devices (Score:2)
From the Intel pdf from http://developer.intel.com/update/departments/init ech/it03012.pdf [intel.com].
So this makes me wonder what the typical number of Serial ATA devices per mobo will be?
clarification - from the spec (Score:4, Informative)
2.1 Goals and objectives
Setial ATA is defined with the following goals and requirements listed in no particular order:
* Primarily inside-the-box storage connection (no outside the box)
* Completely SW transparent w/ ATA (easy transition)
* Low pin count for both host and devices (2 pairs)
* Favorable (low) voltages
* Supports lower cost device architectures
* Higher performance than equivalent ATA (data rate, queuing, overlap) w/ scalability to higher
* Much better cabling/connectors (thin, flexible)
* Includes efficient power delivery
* No software dependency. Relatively easy transition (price, IHV NRE and capital inventory risk, wide variety of devices at intro, etc.)
* Power management and power consunption suitable for mobile use
* Allows roadmap spanning ~10 years
* Cable length comparable to ATA (<1 m)
* Transfer rate exceeding best ATA (~150 MB/s) with scalability to higher rates
* Light protocol allowing overhead latencies to be minimized
* Asynchronous only (no isochronous requirements)
* No Peer-peer transfer support (to/from host only)
* Provides support for 1st party DMA access to host
* Cost competitive with equivalent parallel ATA solution at introduction (host + device + cable)
* Storage device centric (no cameras/scanners/printers)
* Easy installation/configuration (plug/play, no jumpers, no external terminators)
* Single host (no multi-initiators or host/host networking)
Reliability (Score:2)
Re:Good reason cited for not... (Score:2)
Now it's not at all unusual to buy a new computer and find that every drive connector is taken because you have a DVD and CD-R on one channel, and two hard drives on the other.
Cabling issues will be a big benefit to OEMs, and end users who have fewer tech issues with adding drives, as it will be impossible to wire improperly and master/slave/cs jumpers will no longer exist.
If it was only speed improvements I tend to think nobody would care very much.
Re:Good reason cited for not... (Score:2)
Once everyone is using serial ata and software no longer expects a limit of 2 devices per controller I think it goes up to whatever limit (7,15?). Ahh, i'm too lazy at the moment to look it up
Re:Good reason cited for not... (Score:2)
I've had plenty of drives that didn't work well with CS, that's why eliminating the whole configuration issue is a big step. CS is a patch to the problem, but it doesn't eliminate it 100%
Mixing a sony CD-R with a Teac DVD-ROM both with CS and things like that sometimes cause weird issues. I had two drives where if one was first and the other second it would work on CS, but not reversed, unless I locked the master/slave correctly...
Re:Why is it faster? (Score:2, Interesting)
When you transfer data at high speed with cheep cables like the normal IDE once, the signals in the different cables tend to polute each other.
Three different solution exists to this problem:
1. We could build better cables (like the ones you usualy have with Ultra2/Ultra160/320 scsi interface).
2. We could send the data with cheap cables but with a better error correction. (like is done with ATA66/100/133)
3. We could develop a serial interface.(Like Serial ATA)
Re:Why is serial ATA faster? (Score:3, Interesting)
performance capacity. By contrast, Serial ATA's roadmap starts at 1.5 gigabits per second
(equivalent to a data rate of 150 MB/s) and migrates to 3.0 gigabits per second (300 MB/s), then
to 6.0 gigabits per second (600 MB/s). This roadmap supports up to 10 years of storage
evolution, based on historical trends.
Re:Why is serial ATA faster? (Score:5, Informative)
> why serial ATA is faster than the current
> (parallel) ATA?
>
> On PC's, parallel ports are significantly
> faster than serial ports because they transmit
> 8 bits at a time instead of serial's one bit at
> a time. Wouldn't the same thing hold true for
> parallel vs serial ATA?
>
> Please explain.
In a perfect world, parallel would always be faster than serial. However, what happens is that due to outside factors (shape of the cable, EM interference at the time, etc) when you send those 8 bits down a parallel port, they don't all arrive at the destination at exactly the same time. The faster you send them, the more likely they are to not arrive when you send them since your tolerances get lower. This is referred to as signal skew.
Serial ATA borrows a technique from LVD SCSI devices which is low-voltage differential signaling. They send the pulses down 2 lines polarity reversed. By using 2 wires instead of 9 (8 data bits + a clock) or in UDMA land 20 wires (16 data lines, IOR, IOW, DMARQ, DREQ) the chances of them being significantly different than one another is less, because they're closer to following a consistent path through space. This allows them to toggle the lines MUCH faster in LVD applications than parallel applications, which gives us much higher data rates.
Another thing is that the IDE bus still uses TTL signal levels (5V/0V), meaning that it takes a HUGE amount of power to wiggle all those 40 conductors up and down to get some data across. The little chipsets on motherboards these days have trouble supplying enough internal power to do that, so LVD will help them make less complicated circuits in the chipset to talk serial ATA.
eric
Re:SATA design (Score:2)