Rambus and DDR RAM writeup 51
jerkychew writes "Hannibal over at Ars Technica has written part 3 of his RAM guide,, this time focusing on the technical details of Rambus and DDR RAM. As always, a good (if compliacted)technical read. " If you're not scared of pin counts and parity, then this is a cool article.
Time to jump on the bandwagon (Score:1)
Think of the Speed of Light (Score:1)
Forget about using Rambus with much higher clock rates or for very large memories. Of course, they could achieve some performance increase by shrinking the physical size of memory. But this is impossible when Rambus already runs very hot, so hot that not all chips can be "on" at once. Maybe in a decade or two when process dimensions will shrink by an order of magnitude or so!
Rambus proposes a double bank solution. Wait a minute, I thought that their original selling point was their 16 bit data path and the consequent low pin count. Wow, double banking means a 32 bit data path. I think that the Rambus engineers are doing the "double think" here. Why not just use a 64 bit wide data path like everybody else.
Oh, I forgot, it wouldn't be Rambus any more then.
Re:Okay, since you asked nicely... (Score:1)
Re:Sig11 RAM Guide (Score:1)
1) This article was intended as humor. Obviously for a humor-impaired person such as yourself the subtlety of this fact must have escaped you.
2) While this article does offer more hot air than previous posts, I still believe it is very funny. Obviously there are technical problems in compressing hot air, and we're working on them, but I still believe it is better than the use of cold-air in the post-modern 3rd wave era of bullsh*tting.
3)AMD has nothing to do with this article. For that matter, neither does Rambus, DDR SDRAM, the pope, or my left over bag of doritos chips.
4) It would take far less time if you would just start seeing things my way.
5) This is where the reader stopped.
Sig11 RAM Guide (Score:1)
-----------------
(Note: This article has been reformatted to fit your screen, and editted for slashdot-PCness)
Rambus - Evil standard put out by Intel. It's bad, really bad. You should never buy it no matter what. Why? Because Intel is an evil bad corporation that made lots of money. Buy AMD instead.. they, uhh.. made less money! Alternatively, buy the chips and drill holes in them to let out the evil spirits before use.
SDRAM DDR - Horray! Our savior! This type of RAM has none of the evil problems Rambus has (which, for space, we are choosing not to reproduce said list of problems), and they're made by a bunch of l335 d00ds fighting the evil Intel empire. Nevermind that they're produced overseas in sweatshops like Nike shoes and the people on the assembly line deal with chemicals that could take the paint off your car in 5 seconds flat... they are l335!
Re:DDR SDRAM (Score:1)
Re:DDR SDRAM? Not until the lawsuits clear ... (Score:1)
and if you read my post.. (Score:1)
you'd see that i said it was broken, and it is
sorry foolio, you fail!
...dave
and that is enough to be annoying :) (Score:1)
thus my link
i'm not karma whoring
...dave
Re:WTF (Score:1)
Apologies.... (Score:1)
I was all excited to see my posting on slashdot, until I read it and saw all the mistakes I made. Now I feel like a doofus
And, yes, I even used the preview button. Unfortunately, all I checked was the HTML formatting. Live and learn, I guess.
Re:WTF (Score:1)
HELLO, guys, see the connection... (Score:1)
While in theory it does reduce complexity, there is a cost, as this article points out. And when you get down to it, RDRAM fits exactly into this category of "serial protocol"... basically it's making it go four times as fast down a pipe four times as narrow! Now, while Intel may be having second thoughts about this (internally of course), it still seems like another one of the serial protocols they're trying to promote, for better or worse.
I just saw the connection and had to share it.
-----
Re:That doesn't even make sense (Score:1)
In fact, a single rambus channel has full CAS bandwidth down to a 16byte transfer size. After that you are limited by the CAS bandwidth.
This is actually a lot better than some of the proposals for DDR-II
Re:Breaking News: Rambus not that bad (Score:1)
Re:Did anyone notice the lack of opinion? (Score:1)
I'd say that's because it isn't a review. It's a technical explination of why Rambus is the way it is. The explination serves to shed light on what sort of goals were in mind and what sacrifices were made to get there. Combined with the first two parts of the series, and the rest to come, it's more of a history book than an editorial.
Personally, I like seeing articles that are informative like this, without getting into a "which one is better" match. If people read them, and (gasp) learn from them, then they can be better informed to make their own opinion, rather than just "Rambus baaad! DDR goood!". I've made my decision (mainly though choosing the other chip), but it's interesting to read nonetheless.
Re:Did you notice that there's a second part? (Score:1)
Did anyone notice the lack of opinion? (Score:1)
It's like Ars has been castrated. They didn't really make any commitments to talk about which they thought was better; The only time they really complimented RDRAM they said that it had better bandwidth than normal SDRAM but wouldn't mention DDR SDRAM at that point. They also said that RDRAM had some benefit or other, "But this has problems as we will discuss in our next installment."
What pansies. If you can't say what you feel, then you have lost your ability to report the news. Tell us what we need to know, don't give us the marketing data. We can get that from the company webpages.
Re:Think of the Speed of Light (Score:1)
You obviously have never heard of a wave-pipeline either.
You obviously should not be posting to this thread.
-bitMonster
Re:Sig11 RAM Guide (Score:1)
> 1) More parts (thus, higher cost)
Wrong. You use fewer parts to get the same bandwidth.
On the other hand, there is more logic on the die, so the cost is higher. It *should* be a very tiny fraction, though. The reduced cost of the packages due to lower pin-counts *should* offset this. We're all waiting on that....
> 2) Only access 1/2 the banks of memory at a time.
This is a minor issue, considering that you still have 4 times as many banks as in PC100/133 SDRAM.
The memory controller needs to be smarter, though.
Speaking of which, why aren't any of these PC-hacker news sites looking at why the Intel DRAM controllers suck so badly, and always have. Intel has traditionally optimized the price/performance of their chipsets for the desktop and value markets. Studying the specs on their SDRAM controller is considered a good baseline. As in, "Well, at least it's more efficient than Intel's." This isn't surprising to me, because everyone at Intel knows that MHz sells new {boxes|chipsets|CPUs}. I, on the other hand, would shell out money for a new chipset that increased DRAM efficiency by 20%.
-bitMonster, who designs memory controllers for fun and profit. Well, mostly for profit.
Re:and if you read my post.. (Score:1)
-- Sig (120 chars) --
Your friendly neighborhood mIRC scripter.
Re:DDR SDRAM? Not until the lawsuits clear ... (Score:1)
Re:Apologies.... (Score:1)
What, praytell, is this fundamental limitation? (Score:1)
All really, it's quite simple (Score:1)
A processor with an integrated RDRAM controller will be able to have low access latency and extremely high bandwidth (keep in mind that you haven't seen a processor with an integrated RDRAM controller, yet, so the current benchmarks should be taken with a grain of salt). The next generation of processors will have to use RDRAM to compete, because there isn't currently a good high-bandwidth alternative that scales.
Would I want a PC with Rambus? No, not today and probably not for a few years. But servers and workstations are a different animal.
Okay, since you asked nicely... (Score:1)
As for latency, Intel did a poor implementation in which the memory controller was in the chip-set, and communicated with the processor over a standard bus. A better idea is to do what Alpha is doing, and place the RDRAM controller on-chip, which reduces the latency signifigantly.
Asympotically, there is no comparison. Processors will get more and more bandwidth hungry, and RDRAM will always supply much more bandwidth than SDRAM for an equivalent pin count (because of the pipelined--optimized data path with synced clock). Latency will be corrected by better implementations (although it will never rival SDRAM). Latency to memory is not quite as important as everyone here would have you believe, and it will become less so as caches get larger and better.
That doesn't even make sense (Score:1)
Breaking News: Rambus not that bad (Score:1)
As I've said many times in the past, in the future, memory will look more and more like Rambus and less like DDR SRAM.
In a bus-based SMP machine? Yes, Alpha is doing it (Score:1)
Yes they are aware, and what I'm saying is that (Score:1)
Well, if you buy 12,000 of them, they'll cut you (Score:1)
|C|o |m|p|a|q| sells 12,000 Processor EV68 machine to DOD [compaq.com]
Exactly (Score:1)
And as far as which one is "better" it all depends on the situation. (I say as much in my intro to the Rambus section.) Individual technologies are "better" or "worse" for _particular applications_. Depending on the constraints that you're operating under (cost, latency, bandwidth, availability, granularity, etc.) one solution will fit your needs better than another one.
Yeah, sometimes it's easy to make a clear call on which of two similar technologies is better for 99% of the applications out there, like if you're comparing FPM RAM to EDO RAM. But Rambus is complex enough and different enough from DDR SDRAM to where it's not always a black and white issue. Rambus has advantages that make it better for certain applications, and DDR DRAM has advantages that make
But again, there are no benchmarks in the article, nor will there be. There are plenty of places where you can find out how an RDRAM system configured a certain way stacks up against a similarly configured DDR DRAM system running a certain set of application benchmarks. I'd suggest you check out one of those to see which technology best suits your particular needs. If you're just curious about how it all works, though, I hope my article can be of some help to you.
I hate to spoil the fun here but ddram is toast (Score:2)
one word, PATENTS!
Rambus owns the intellectual property of virtually every syncronized ram chip in existance (including ddr)and also including a really scary patent on using a register to address memory!
I know you guys probably just read the previous story here about a guy who now claims that internet stock transactions are his own personal property and the last thing you want to hear are more greedy corporations and whining but they are a real problem.
The only reason sdram is still here is that rambus made it available cheaply now to show that there is competition to the fcc and also to highlight rambus as the next big thing. Rambus promissed no ddr ram chips in large qualitites would ever be introduced without big lawsuits.
I also read a news article on zdnet explaining that the p4 will be rambus only.
As the chip becomes standard expect ddr ram to slowly vanish and people will all forget about ddram since all the vendors like compusa and directwarehouse wont stock ddr because the demand will be too low (remember AMD hardly made a dent in intels armour. Many bussinesses only buy computers with intel chips).
As soon as the ddr is made in smaller and smaller quantities the price to manufacter will go up making it even more expensive then rambus (remember rambus will sue othe memory manufactors unless its priced much higher then rambus.
Company officals admitted they will try this tactic to wipe out ddr.
I believe sadly that amd's sledghammer will als be rambus only (correct if I am wrong guys. I would be happy if I was.). I thought I saw an article here on slashdot that amd finally gave in to rambus demands.
Its a shame supperior technology will be blocked again.
Remember to write to your politicians on patent abuse because its really hurting us.
not quite (Score:2)
Pope
Freedom is Slavery! Ignorance is Strength! Monopolies offer Choice!
there were no good links,.. (Score:2)
on ars (the ones at the bottom are broken and point to part III), so here they are :
part I [arstechnica.com]
and
part II [arstechnica.com]
these are really good, and very educational!
...dave
Re:Your sarcasm hides a truth that is unwelcome he (Score:2)
All the information I have read has pointed to the latency as a killing factor to RD-DRAM. While RD-RAM has faster access, it is only 16 bits at a time, which puts it with DDR-DRAM. If there is something that myself or others don't understand about RD-RAM which will make it better for future use could please allaberate more then just saying Rambus is actually a solid and viable memory technology? I have heard many techinical arguments against it. I am willing to hear arguments for it but I haven't heard any yet so if you have some please post them as I am more interested in the truth then in personal bias.
Molog
So Linus, what are we doing tonight?
Re:Sig11 RAM Guide (Score:2)
1) Rambus is not a standard put out by Intel. Rambus is not even a standard at all. Rambus is a company which makes its money by licensing their intellectual property. Rambus Direct DRAM (RD-DRAM) is a standard put out by Rambus which outlines how to manufacture and communicate with their memory technology. Rambus licenses this to memory and chipset manufacturers such as Intel, NEC, and Samsung. FYI AMD also has a Rambus license, but they have done nothing with it.
2) While RD-DRAM does offer higher bandwidth than traditional SDRAM, its implementation brings about a whole bunch of other problems. Neither RAM standard is perfect, however DDR-SDRAM has better performance than RD-DRAM in almost all scenarios, and it's CHEAPER because A) no licensing fees and B) it's very very similar to SDRAM so fabrication plants can simply modify their existing production lines instead of creating whole seperate lines for RD-DRAM.
3) AMD has nothing to do with Rambus or DDR SDRAM. When you buy RAM you are not "buying Intel" or "Buying AMD." That's like saying you're "buying Honda" when you buy some Firestone tires that fit your Honda. [sarcasm]And of course we shouldn't buy Honda because they are an evil Japanese corporation, and Japan is where Pokémon came from, which is the spawn of Satan.[/sarcasm]
4) Intel is pushing the RD-DRAM standard because of an agreement with Rambus which, if they can make RDDRAM successful, they get enormous amounts of Rambus stock. Basically Rambus bribed Intel in order to get their superior product out there so they could make more licensing fee money.
5) Intel is NOT ALLOWED to market a DDR-SDRAM chipset for high-end desktop machines under the terms of this agreement. All this talk about Intel making a DDR-SDRAM chipset for regular PCs are foolish. They may try to produce a "server chipset" which supports DDR-SDRAM, but you will not see a high-end PC chipset from Intel which supports DDR-SDRAM. Note that the chipset must be made by Intel, that's not to say VIA or SiS can't make one.
6) Rambus is produced in the same fabrication facilities as SDRAM.
7) It's l337 or 1337, not l335.
Re:All really, it's quite simple (Score:2)
RDRAM is technology that was good in the mid 90s but which has been surpassed by DDR SRAM. Making DDR SRAM scale is a far simpler problem than making RDRAM efficient. People tend to solve the simpler problems first.
Re:What, praytell, is this fundamental limitation? (Score:2)
I'm sure the engineers designing the Alpha EV7 are perfectly well aware of the limitations of Rambus technology. Probably more so than I am.
Re:That doesn't even make sense (Score:2)
Re:Yes they are aware, and what I'm saying is that (Score:2)
Glad we finally got there. Whew! ;)
Re:That doesn't even make sense (Score:2)
Is that simple enough to understand, or is my crack-addled brain going too fast for you?
Re:Breaking News: Rambus not that bad (Score:2)
I've been using Rambus parts for years (N64, now PS2) and the performance just isn't that great. Performance is what people like, not cool designs or easy board layout. The theoretical performance isn't even that important - it's the massive complexity of the RDRAM controller on the FSB which drags the actual numbers down. Add to that the fact that RDRAM bandwidth is only 1/3 of theoretical bandwidth even in the best case, unless you have multiple channels open simultaneously. Great for multiproc servers, perhaps, but lousy for singleproc desktop machines.
So, I'd be interested to know, why do you think future memory will be more like Rambus and less like SRAM?
Re:Breaking News: Rambus not that bad (Score:2)
Compliacted? (Score:2)
DDR SDRAM (Score:2)
Vote [dragonswest.com] Naked 2000
Your sarcasm hides a truth that is unwelcome here (Score:2)
DDR SDRAM? Not until the lawsuits clear ... (Score:3)
June 16: Toshiba signed agreements with Rambus, Inc to pay Rambus royalties on SDRAM and DDR RAM based products. This development has the potential to seriously shake up the memory market. Toshiba has just set a precedent, and basically sold out the rest of the world's memory manufacturers.
Basically, Rambus is making Toshiba pay huge $$$ to make and market DDR SDRAM. In that article, it states that the royalty rate is even higher than RDRAM. (which we all know is way overpriced!)
Later on in the month, The Register ran this article: http://www.theregister.co.uk/content/3/11576.html
This one is by Hitachi which is counter suing Rambus stating they have an unfair monopoly on memory. Now I'm no lawyer, but reading these articles
Taken from the register piece:
Hitachi admits that the '804 Patent was issued to Rambus on September 21, 1999, and is entitled "Synchronous Memory Device Having An Internal Register."
There's more legal stuff in there
:P
Re:Sig11 RAM Guide (Score:3)
1) More parts (thus, higher cost)
2) Only access 1/2 the banks of memory at a time.
3) RAMBUS claiming patents for SDRAM production doesn't make their case any better as well.
That being said, will RAMBUS (aside from the political issues) give better performance..say...5 years from now, when we all have 2Ghz machines running with an 800Mhz FSB motherboard? Some of what I've seen implies that the performance is really nasty right now, but in a few years when CPU and FSB speeds increase, it could pick up more performance.
Re:DDR SDRAM (addendum) (Score:3)
Maybe I should just tighten the belt and go for the 1040MHz Alpha [theregister.co.uk] (w/DDR, AGPx2)
Vote [dragonswest.com] Naked 2000
Re:DDR SDRAM? Not until the lawsuits clear ... (Score:4)
Rambus is a member of the JEDEC, a committee of Semiconductor manufacturers which was created to help set standards for different types of chips. All the major manufacturers are JEDEC members, as well as other companies including Intel and Rambus.
One of the agreements to joining the JEDEC is that you must disclose all patents, finalized and pending, to the committee and you may not withhold such information, or use information gained in the JEDEC forums to file your own patents.
Rambus decided not to follow the agreement, and instead filed a patent during the SDRAM standard negotiations which would attempt to patent the exact implementation of SDRAM which was being written up. In the patent office, if your patent is not granted you can get extensions on it by modifying it. So what they did is continually string the patent along for several years, modifying it slightly so that as the SDRAM (and later DDR-SDRAM standard) was finalized, their patent looked exactly like what the standard was supposed to be.
Now the patent finally went through (god bless those morons in the patent office), and since everyone has implemented their RAM according to the standard, Rambus is suing them all for patent infringement.
However, there is very little chance they'll win. First, they violated the JEDEC agreement. Second, there is certainly prior art. Third, there was a decision back in '96 (I think) against Dell Computer when they patented something which was the result of "An Industry-wide Standardization effort" where the courts ruled that their patent was unenforceable. This is going to happen to Rambus, as well.
As for Hitachi and Toshiba backing down and paying license agreements there are specific reasons.
After the settlement, Hitachi sold their RAM division to NEC. They don't have to deal with the problem now, and since NEC is incorporating Hitachi's RAM infrastructure into their own, the licensing agreements probably mean jack now.
Toshiba, on the other hand, manufactures the RD-DRAM which is used in the PlayStation 2. They're making enormous amounts of money from this, and if they didn't agree to pay more licensing fees to Rambus, Rambus might pull their RD-DRAM license, thus forcing Sony to find someone else to manufacture the RAM.
Hope this has been informative...