Behind the 4GB Memory Limit In 32-Bit Windows 756
An anonymous reader points us to a very detailed post by Geoff Chappell, first put up early this year, explaining how the 4GB memory limit commonly bandied about for 32-bit Windows (he is writing mainly about Vista) is more of a licensing preference than an architectural limit. The article outlines how Chappell unlocked his system to use all the memory that is present, but cautions that such hackery is ill-advised for several reasons, including legal ones. "If you want [to be able to use more than 4GB in Vista] without contrivance, then pester Microsoft for an upgrade of the license data or at least for a credible, detailed reasoning of its policy for licensing your use of your computer's memory. ... [C]onsider Windows Server 2008. For the loader and kernel in Windows Vista SP1 (and, by the way, for the overwhelming majority of all executables), the corresponding executable in Windows Server 2008 is exactly the same, byte for byte. Yet Microsoft sells 32-bit Windows Server 2008 for use with as much as 64GB of memory. Does Microsoft really mean to say that when it re-badges these same executables as Windows Vista SP1, they suddenly acquire an architectural limit of 4GB? Or is it that a driver for Windows Server 2008 is safe for using with memory above 4GB as long as you don't let it interact with the identical executables from Windows Vista SP1?"
I don't understand... (Score:5, Funny)
is more of a licensing preference then an architectural limit
So it's a licensing preference, followed by an architectural limit? If so, how is this a story?
Re:I don't understand... (Score:4, Funny)
No, it's a licensing limit..
I think you missed the point of the parent. Schon was wittily illustrating the grammar mistake (then/than) and the effect it has on the meaning of the statement.
An appropriate response would have been something equally witty such as, "Well I don't know about you but I'd rather have 4GB then 32GB!"
Re:I don't understand... Simple: Greed. (Score:4, Informative)
They should be selling the 64-bit version. They should be preinstalling the 64-bit version. People *shouldn't* be using the 32-bit version, becuase there's still a very real architectural limitation in the 32-bit version: a given process can only see 3 GB of memory, no matter how you set up your licensing.
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And software support, ask Intuit if their latest software in the Quicken line of accounting and retail software will run in 64bit windows.
Nobody needs more than 640K of RAM (Score:4, Insightful)
Now they will say nobody needs more than 4G of RAM.
I remember back in the day when 8M of RAM was considered too much.
Looks like Microsoft will force upgrades to Windows 7 to get over the 4G RAM limits?
Ah for the days of the AST Rampage card that got over the 640M RAM limits using EMM/EMS memory standards. Can't someone just write a RAM extender driver for 32 bit Windows for XP and Vista to get over the 4G RAM limit?
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Looks like Microsoft will force upgrades to Windows 7 to get over the 4G RAM limits?
I doubt 32-bit Win7 will drop this limitation. Also, you can already use more than 4GB RAM in 64-bit editions of XP and Vista.
Ah for the days of the AST Rampage card that got over the 640M RAM limits using EMM/EMS memory standards. Can't someone just write a RAM extender driver for 32 bit Windows for XP and Vista to get over the 4G RAM limit?
Not likely, NT-based OSes (WinNT, 2000,XP, 2003, Vista, 2008, and 7) are not DOS, and the methods of accessing memory are not the same. EMM386 was designed to access higher areas of memory in 16-bit and 16/32 hybrid operating systems(DOS, Win9x + ME). NT is an actual 32-bit OS with flat memory addressing.
Besides, this isn't a technical limitation, this is an imposed limit by Microsof
Re:Nobody needs more than 640K of RAM (Score:4, Informative)
That's what PAE is. To the process, the address space is just one huge flat expanse from 00000000 to 7FFFFFFF. (or BFFFFFFF if the OS is configured that way and the software understands it) To the OS, the processes are allocated RAM in 4 kB pages which are mapped to their corresponding hardware frames in RAM via the page table. When the process accesses an address, the low 12 bits determine where within the page it should read, while the high 20 bits determine the entry in the page table. That entry has the hardware address which it then accesses. PAE allows the hardware address to be larger than 20 bits so that the OS can address more than 32 bits of physical memory transparently to the individual processes.
Re:Nobody needs more than 640K of RAM (Score:4, Funny)
idk my BFFFFFFF jill?
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Nope, Windows 7 x86 RTM (32-bit), with 4GB of physical ram "3.25GB Usable" per the computer properties screen.
Re:Nobody needs more than 640K of RAM (Score:4, Informative)
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Whether users need it or not, new computers are going to start including more than 4 GB sooner or later by default.
Which isn't really a problem, in that the newer 64-bit OS's support those quantities of RAM just fine. When XP 64-bit first came about it wasn't really ready for prime-time, but Vista 64 and Windows 7 64-bit are pretty much identical to their 32-bit cousins.
Aside from obscure legacy needs, I don't see any reason why a new user wouldn't go for the 64-bit versions, and if you have to run obscure legacy hardware or software, then you have to (and always have had to) live with some restrictions cause by that.
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Use bank switching... (Score:3, Interesting)
That's how my Commodore=128 got around the 64k limitation of its CPU, and could access upto 16 banks or 1 megabyte of RAM.
If the same technology was used with 32 banks of Windows XP space, you could get 128 gigabytes.
Re:Use bank switching... (Score:4, Insightful)
Did you read the article? (No, you didn't) It points out most modern Windows systems automatically use PAE because Microsoft has turned on DEP by default where supported. It appears 32bit desktop Windows has a limitation imposed by the licensing code since around XP SP2, not some option you can disable. It also points out most applications don't use anywhere near 4GB of memory (yet at least) and the primary practical use of that much RAM these days IS multiple applications.
Simple (Score:5, Informative)
Windows Server 2008 drivers have to be signed. For them to get signed, they can't do stupid shit like assume they are loaded in the memory space between 3GB->4GB, I'd imagine.
Re:Simple (Score:5, Funny)
...they can't do stupid shit like assume they are loaded in the memory space between 3GB->4GB, I'd imagine.
You must be new here...
Word for the wise (Score:5, Informative)
On a 32-bit system a single process will always be limited to 4 GB due to the number of address bits, unless the programmer goes through hoops to access a larger memory area one small piece at a time (tricks like that were common in the DOS era -- anyone remember EMS?). On Windows the kernel typically reserves one half of the address space, cutting the usable memory of a single process down to 2 GB. Thus you won't get much advantage from a 64 GB capable kernel unless you run multiple programs that all require 1-2 GB of memory. Come to think of it, such usage is most likely on a server.
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Re:Word for the wise (Score:5, Informative)
Then get a 64-bit OS and be happy.
PAE is a hack. Even if your copy of windows supports it, it still sucks. It doesn't actually grant the ability to access all 64GB at the same time, it only lets you access it in 4GB windows, so your app has to jump through a lot of hoops to be able to actually use that memory. It was a decent solution for having large databases in the 32-bit era, and that was rightly the only place it should be used. Today, 64 bit cpus are completely mainstream and vastly superior for handling large amounts of data.
Frankly, in the era of 64-bit budget computers, I think calling the 4GB limit "architectural" is as fair as saying the 286 had a 1MB limit after the introduction of the 386. Technically not completely accurate, but for most nearly all practical purposes it drives the listener in the right direction, which is getting the product which doesn't have the restriction in any way.
Re:Word for the wise (Score:4, Informative)
Then get a 64-bit OS and be happy.
I agree.
PAE is a hack.
I disagree. Paging is fundamental to memory management. You like having memory mapped to 4KB pages, but call it a hack when those 4KB pages are mapped to different physical memory locations? Why?
Apparently PAE is even more efficient than 64bit addressing. It's the faster option, although you're 100% correct about the per-process limit being roughly 3GB, which means it'll be obsolete shortly. Games, video editing, and virtual machines will be first to benefit from 64bit > 4GB memory usage.
What I've always wondered is why Windows uses 4KB pages. Larger pages are far more efficient. The guy who made 7-zip tried hacking in multi-megabyte pages, and had a 15% speedup. O_o
Re:Word for the wise (Score:4, Informative)
Complete BS, PAE isn't a hack, in fact the way paging is done on x86-64 is designed very similarly to 32-bit with PAE, using an extra layer of indirection as PAE does. (Yes your 64-bit CPU actually likely has 48-bit's of **physical** memory).
Also, you are completely ignoring things like disk cache, which can massively improve system performance. Sure no **single** application will be able to use all of that memory, but the system as a whole can easily get that high if it has the RAM to work with.
For example, I have a Linux box with 4GB of RAM using a 32-bit with PAE kernel. Routinely after a few hours my disk cache is upwards of 3GB. The system is noticeably faster once the disk cache is populated vs immediately after startup.
Take a look at the Intel docs, PAE isn't a hack in any way.
Re: (Score:3, Interesting)
Windows 64 bit runs either 32 or 64 bit apps pretty seemlessly. The big disadvantage of being 64 bit is that Microsoft has dropped all 16 bit support in their 64 bit operating systems. For 99.5% of people, this is fine.
The other .5% are like me and still have some 16 bit software they are really old games from the Win 3.1 days I still love (sim tower and others), or old utilities from mid 90s that haven't been replaced simply because I am used to them and they work.
For these, virtualPC is the only option
Re:Word for the wise (Score:5, Informative)
Yea, but even if you enable 16GB of RAM under 32bit Windows, XP and Vista can only give 2GB of it to photoshop, MAX. No SINGLE application can utilize more than 4GB of virtual address space under PAE, had half the address space is reserved for the lernel. PAE however is disabl;ed under 32bit OS as it has risks, especially for lots of drivers, and letting general users have access to this, without a process for validating and supporting all their apps under it (which most companies do not have programmers who understand this type of addressing), would be a support nightmare. PAE works when lots of individual apps need to run concurrently, or when multiple instances of the same app need to run under seperated memory spaces. Both these cases are uncommon for workstation users, and the 64 bit edition solves this issue for most users who would take advantage of it, so PAE is not included in workstation OS by Microsoft. This is NOT a licencing issue, or even a "charge more for advanced features" issue, it;s about who needs it, how much it costs to support it, and whether or not the SHOULD be using it vs other options...
Its possible for an application under 32bit windows to also take advantage of AWE (Address Windowing Extension). This requires the lock Pages in Memory privilidge for the app, and some pretty extensive code level support. This can allow a 32 bit app to use more than 4GB of RAM under 32bit. It is not very efficient. It;s also one of the API's you're paying extra for under the server licnece that you do not get under the workstation license (XP can't do this, Server 2003 can). Typically this is reserved for apps with massive datasets (DBs over 2GB, large video files, massive images, etc) in situations where the code can not be easily ported to 64bit but where support for AWE can be added.
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But this is a huge hack, and can still cause issues with drivers etc still believing that the kernel has reserved half the ram, but is instead restricted to the top 1gb.
Re:Word for the wise (Score:4, Insightful)
Sigh... allow me to point out how you are wrong in virtually everything you said.
Yea, but even if you enable 16GB of RAM under 32bit Windows, XP and Vista can only give 2GB of it to photoshop, MAX. No SINGLE application can utilize more than 4GB of virtual address space under PAE, had half the address space is reserved for the lernel.
Any application can easily access up to 3GB of memory directly, use the /3GB switch when booting. Using more than 3GB requires PAE and indirect addressing like the days of old.
PAE however is disabl;ed under 32bit OS as it has risks, especially for lots of drivers, and letting general users have access to this, without a process for validating and supporting all their apps under it (which most companies do not have programmers who understand this type of addressing), would be a support nightmare.
No its not, PAE is FOR 32 bit OSes, 64bit OSes don't need PAE, they can directly access the larger amounts of ram. PAE will be useful for running lots of apps that aren't aware of the API to utilize the extra memory, or allow apps that use the proper API to indirectly address larger amounts of ram, which is FAR faster than using some sort of swap like Photoshop does when it needs more RAM than available. PAE is turned on by default on clean installs of Windows XP SP2 so that DEP (The no execute bit) can function as the code in XP requires it.
Its possible for an application under 32bit windows to also take advantage of AWE (Address Windowing Extension). This requires the lock Pages in Memory privilidge for the app, and some pretty extensive code level support. This can allow a 32 bit app to use more than 4GB of RAM under 32bit. It is not very efficient.
Two things, first you just contridicted pretty much everything you wrote before this point, and second its FAR FAR more efficient than using disk based swap of some sort.
It;s also one of the API's you're paying extra for under the server licnece that you do not get under the workstation license (XP can't do this, Server 2003 can). Typically this is reserved for apps with massive datasets (DBs over 2GB, large video files, massive images, etc) in situations where the code can not be easily ported to 64bit but where support for AWE can be added.
Funny, works on my XP machine, not sure why it doesn't work for yours. Photoshop is fully aware of the extensions and will be happy to use more than 3GB of ram in XP 32 bit if you have more available.
Why must you people spew shit you have no clue about, to the point that you contradict yourself in your own post. If you're going to do this shit at least read the entire wikipedia page before you start posting rather than bit by bit as you post, it'll make you a little more believable and you'll get some extra knowledge too.
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The problem is (Score:3, Informative)
That for an app to use more than 2GB of memory on a PAE enabled system, the app itself has to specially support and use AWE (address windowing extension). Only apps that are coded to do that can make sure of more than 2GB. Well those are extremely rare. MSSQL server is the only one I know of. Any other apps is still limited to 2GB.
No such problems on a 64-bit system. Each 32-bit app gets 4GB of virtual address space. That means normal apps can access 2GB of memory, any app flagged as large address aware can
Let's just get over this and move to 64bit (Score:4, Insightful)
Seriously, there are no real technical reasons why we can't just run 64bit operating systems. Let's just stop selling 32bit ones.
Re: Let's just get over this and move to 64bit (Score:5, Informative)
Seriously, there are no real technical reasons why we can't just run 64bit operating systems. Let's just stop selling 32bit ones.
Good idea.
Unfortunately, lots of Windows software won't run on 64-bit Windows XP. Even Windows Update tells you you have to close the 64-bit WIE so it can run the 32-bit version to fetch the update... how lame. Then half the updates won't install, for reasons that aren't made clear.
It should be clear by now that Microsoft, like every other corporation on the planet, isn't going to do a damn thing unless their share prices depend on it. When there's overwhelming consumer demand for 64-bit computing, they'll start fixing their consumer software to support it.
Re: (Score:3, Interesting)
Unfortunately, lots of Windows software won't run on 64-bit Windows XP.
I have no issue at all running standard 32-bit apps on XP64.
Most of the software that won't run is shell extensions, or other software that provides some DLL that must be loaded by other apps (like Microsoft Management Console plugins). Some of this can be worked around if there are both 32 and 64-bit versions of the app, and then you might not be able to use all the plugins you want at the same time, but at least you can get the job done. Because of this, the default for multi-version apps is usually the
Like? (Score:3, Informative)
Seriously, what apps don't run in 64-bit Windows? I ask because I run 64-bit Windows at home and at work, and part of what I do is check our apps for compatibility. Here is a list of some of the programs I've tested and verified work in 64-bit Windows. This is not a complete list, just off the top of my head:
Matlab 2008, HFSS 11, ADS 2008, VMWare 6.5, Visual Studio 2008, Firefox 3.5, Thunderbird 2, Office 2007, Adobe Audition 3, Sony Vegas 8, Geovision Multiview 8.3, Winamp 5, 7zip, Sonar 8, Play 1.2.5, Tex
Just Recompile it (Score:5, Funny)
What's the problem? Just grab the source and recompile it.
Re: (Score:3, Interesting)
In what way is it terrible? Driver availibility isn't brilliant and the lack of a netware client is annoying but other than that I haven't noticed any real problems with it.
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Excuse me, but both Linux and Mac OS X have very, very good support for 32-bits apps under a 64-bit OS. The only ones that don't seem to be able to pull it off is Microsoft. I had to install Windows XP 64-bit last week for someone trying to access all memory in their machine and a) none of the drivers worked, even for simple things like USB and other 'generic' hardware where in Linux or Mac you can load 32-bits kernel extensions or generic USB and network controller drivers b) SP3 is not even available yet
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Excuse me, but both Linux and Mac OS X have very, very good support for 32-bits apps under a 64-bit OS. The only ones that don't seem to be able to pull it off is Microsoft. I had to install Windows XP 64-bit last week for someone trying to access all memory in their machine and a) none of the drivers worked, even for simple things like USB and other 'generic' hardware
This is a PITA, the truth is there is little generic hardware in a modern PC, you need specific drivers for almost everything. These drivers
Re:Let's just get over this and move to 64bit (Score:5, Insightful)
there are no real technical reasons
Well, other than for crappy software that assumes that an address is 32 bits...
Or hardware that doesn't have drivers for 64-bit systems...
So, yes, no technical reasons at all...
Re:Let's just get over this and move to 64bit (Score:5, Informative)
Minor technical reason:
64 bit OS's don't run on 32 bit CPUs, which is most of the netbook lines. While there are a few Atom models which are 64 bit, the majority of them are 32 bit. I don't think MS wants to abandon that market to Linux, since it would allow netbooks to become a Linux "gateway drug".
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All NEW Os should be 64 bit, sure. unfortunately, we have to have a 32bit solution that maintains continued support for all the legacy apps we can't leave behind.
Sure, we could "restrict" the sale of 32 bit apps, and restrict all signed apps to 64 bit here forward, and most people buying new machines to work with new stuff, and common apps would not have issues, but about half my back catalog of personal software would either have to be replaced or run in a VM (and currently, many games don't like VM or do
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Re:Let's just get over this and move to 64bit (Score:5, Interesting)
As long as we maintain the ability to run 32-bit programs on those 64-bit operating systems. I have Perl programs that parse and analyze very large log files. Their memory usage went up by a factor of about 1.5 when I switched to a 64-bit system. This was not good, since they were running at about 90% of RAM on the 32-bit system. On the 64-bit system, they swapped heavily, and my nice 10 minute report became a not so nice all day report.
I now pick the 32-bit version of Linux distributions, even on 64-bit capable hardware, unless I actually need 64-bit.
Re: (Score:3, Funny)
Seriously, there are no real technical reasons why we can't just run 64bit operating systems. Let's just stop selling 2-bit ones.
Fixed that for ya.
Re: (Score:3, Interesting)
The Intel Atom: [wikipedia.org]
Atom implements the x86 (IA-32) instruction set; x86-64 is so far only activated for the Atom 230 and 330 desktop models. N and Z series Atom models cannot run x86-64 code.
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There is no reason to support 32-bit right now.
Other than publishers of proprietary applications who won't port them to 64-bit. Some of these publishers are even out of business. Compare to the transition from PowerPC to Intel Macs during the Tiger era: without the Rosetta emulator, it would have been a much rougher experience.
Hmm (Score:5, Insightful)
I skimmed the article.
What it boils down to is : it's possible for 32-bit windows to use more than 4 gigs of memory. Microsoft doesn't allow this for the consumer licensed versions of Windows. While the article makes various allegations that Microsoft is doing this to be bad, the author found out that many device drivers intended for 32 bit windows will break if PAE is enabled. In addition, PAE is an ugly hack, and it still won't let a single thread access more than 3 gigs of RAM. These days, single applications like games and video editing software can easily use more than 3 gigs of RAM.
Long story short : Get, and use 64-bit Windows for Windows machines with a lot of RAM. Since 64-bit XP is poorly supported, and Vista is dog-shit, then that means you should be using 64-bit Windows 7.
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Alternatively you can use any distribution of Linux or BSD released in the last 5 years.
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Aye. Linux is no utopia, though. Truth is, Windows works pretty darn well so long as you cater to it's "special needs" properly.
Aye. Windows is no utopia, though. Truth is, Linux works pretty darn well so long as you cater to it's "special needs" properly.
32b? (Score:4, Insightful)
Are there people out there who have more than 4GB of memory but still run old 32b operating systems? How uncharacteristically anachronistic of any technology enthusiast...
Re:32b? (Score:4, Funny)
You'd be surprised. You see alot of people go into BestFutureBigBlockStoreUSAToday and say "My computer's running slow!" and they go "You need more Rams!" and the customer goes "How much will that cost me?" and they go "300 Bones, and we'll do it for you!" and next thing you know, Blogger Buddy Bill has 8 Gigs of RAM on his 32b XP. And because he paid so much, he insists theres a difference!
Re: (Score:3, Interesting)
Yeah, I hate it. I write software to process large scientific datasets. Corporate IT still will not support 64-bit XP or Vista, so all the scientists/engineers are running 32-bit. It is usually easier to try enabling 3GB user space or PAE and hope their drivers are complaint than it is to get them to upgrade their OS.
Re: (Score:3, Funny)
Are there people out there who have more than 4GB of memory but still run old 32b operating systems?
Yes [ibm.com].
(In all fairness, though, we don't have more than 4GB of memory per processor.)
Re: (Score:3, Informative)
Windows 2000 had (has) everything needed to get past 4Gb.
Windows 2000 only came in 32bit version
If Windows 2000 (PRO) is installed on a machine with 4Gb of RAM it will use it all, even the memory with a physical address above the 4Gb line.
Windows 2000 datacenter can use 32Gb of RAM before it hits it's license limit.
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The inability to run 16 bit windows apps is still there*, driver support has improved though it can still be a problem (for example the first generation ICD2 is never going to get a 64 bit driver)
*and whats more annoying is afaict there is no reason it has to be that way for 16 bit windows apps (for real mode dos apps there are real technical reaons but not for win16 apps) IIRC MS just found some issues and couldn't be bothered fixing them, wine runs 16 bit windows apps on 64 bit linux fine ;).
Market segmentation (Score:5, Insightful)
And in other news, it costs precisely the same to press a copy of Vista Home Crippled versus Vista L337 OMG, and yet Microsoft charges differently based on which bits are enabled on the particular copy that HP installed on your laptop. This called "market segmentation". If you think a proprietary software company's going to give the cheap version all the same features as the expensive one, just because it wouldn't directly cost them more to do so, then you are hopelessly naive.
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The only cost in software production isn't disk pressing.
And lemons are yellow, but that's not what we're talking about. The marginal cost of copying and distributing two different versions of the same OS, assuming similar packaging, is nil. The only reason to ship cheap limited versions is to segment the market.
Fair price??? (Score:4, Insightful)
I dunno... maybe because they think that price maximizes their profitability?
Or do you feel that they're morally obligated to only make a certain profit margin off of their price?
server hardware vs desktop hardware (Score:3, Interesting)
Many server motherboards have more then 4 RAM slots. Many DDR3 desktop motherboards have 6 RAM slots. But it is not uncommon for server motherboards to have 12 or more RAM slots. Can one get 64 GB of RAM with 6 RAM slots? Sure, we can even do it with 4 RAM slots if you can get 16 GB RAM modules. Most people do not do that. And most regular people have no need for 32GB or 64GB of RAM in their desktop. Vista jokes aside, 64GB of RAM should really be in the for servers not desktops. That can be the thinking behind the 4GB of RAM limit for 32 bit desktop operating systems. Most people who use them will not have a need for more then that.
Also when the 4GB of RAM limit was set, RAM was really expensive. RAM prices have dropped a lot over the years. While having 4GB of RAM today can be commonplace, that was not the case 10 years ago.
PAE? Nothing to see... (Score:5, Informative)
This sounds like more PAE shenanigans. Using PAE on 32 bit Windows has already been well covered by The Old New Thing [msdn.com].
Another kdawson special... (Score:5, Insightful)
Why is /. greenlighting yet another article just for the sake of MS-bashing? Other posters have already pointed out the remaining process memory limits and consumer driver issues that make this a non-starter technically. Not to mention that there's not much (any?) consumer-level 32-bit hardware that has BIOS/Northbridge support for more than 4GB of RAM. Since the 64-bit versions don't cost any more, who cares?
But this guy is saying that Microsoft is doing something "illegal" because he was able to hack his system and enable PAE, even though MS charges extra for that in their server OSes. Is it "illegal" for Ford to sell me a car that's computer governed to 105 MPH even though the engine can get it up over 130? Can I complain to the FTC if I chip the car to remove the limit and then destroy the transmission?
On 32 bit WinXP, you can't even use 4 GB (Score:4, Informative)
Even 4GB is too much for 32 bit WinXP. The OS will only let any app. use a maximum of 2 GB. [microsoft.com]
Unless you enable the /3GB switch in boot.ini, which leads to other problems: your registry system hive must now remain smaller than 12 MB. [alma.ch]
Not much content to this story (Score:4, Informative)
Why this is a non-story:
1) MS removed PAE in XP SP2 because of incompatibility with 32 bit drivers and resulting instability issues.
XP did support PAE before SP2. However, Microsoft received complaints from users regarding compatibility and instability issues resulting from the use of 3rd party 32 bit drivers. Many users were getting BSODs. It was only then that MS chose to remove PAE from XP SP2.
This decision makes quite a bit of sense. Manufacturers were unlikely to update drivers to include PAE support because, at the time, 4GB+ of memory was very uncommon, and relegated to power users who had a specific need for large amounts of RAM. The situation has since changed due to the plummeting cost of RAM, Vista's need for greater memory resources, more demanding applications, and Superfetch, which allows users to make use of idle memory to preload commonly used applications. My own experiences on Vista x64 show that programs start up significantly faster than in XP due with Superfetch enabled.
Now that 64 bit drivers can be had for pretty much all modern hardware, there is no reason to use a hack like PAE to support more than 4 GB of RAM. Most machines sold by Dell, HP etc. now include 64 bit Vista if the machine has 4 GB of RAM, which is now becoming standard.
See below for MS's explanation of the removal of PAE from SP2.
Source: MS Website, "Operating Systems and PAE Support", June 14 2006 - http://www.microsoft.com/whdc/system/platform/server/PAE/pae_os.mspx [microsoft.com]
Driver Issues Typically, device drivers must be modified in a number of small ways. Although the actual code changes may be small, they can be difficult. This is because when not using PAE memory addressing, it is possible for a device driver to assume that physical addresses and 32-bit virtual address limits are identical. PAE memory makes this assumption untrue.
Several assumptions and shortcuts that could previously be used safely do not apply. In general, these fall in to three categories:
Buffer alignment in code that allocates and aligns shared memory buffers must be modified so that it does not ignore the upper 32 bits of the physical address. Truncation of addresses information in the many locations this might be kept must be avoided. It is necessary to strictly segregate virtual and physical address references so DMA operations do not transfer information to or from random memory locations.
PAE mode can be enabled on Windows XP SP2, Windows Server 2003 SP1 and later versions of Windows to support hardware-enforced DEP. However, many device drivers designed for these systems may not have been tested on system configurations with PAE enabled. In order to limit the impact to device driver compatibility, changes to the hardware abstraction layer (HAL) were made to Windows XP SP2 and Windows Server 2003 SP1 Standard Edition to limit physical address space to 4 GB. Driver developers are encouraged to read about DEP.
2. Windows isn't trying to screw users over by purchasing a higher priced 64 bit version. Any retail version of Vista or Windows 7 comes with both the 32 and 64 bit installers. As others have mentioned, it's also possible to activate 64 bit Windows with a 32 bit OEM key.
3. PAE will not allow a single process to use more than 4 GB of RAM so a true 64 bit OS is still superior for programs that need large amounts of memory such as HD Video editing, editing of large images in Photoshop etc.
Re:Wa wa what? (Score:5, Informative)
Linux does not have the same limit [wikipedia.org]
Re:Wa wa what? (Score:4, Informative)
But it wont do you a lick of good in MS windows, except for a very few version of windows.
http://msdn.microsoft.com/en-us/library/aa366778(VS.85).aspx [microsoft.com]
Comment removed (Score:5, Insightful)
Comment removed (Score:5, Informative)
Re:Wa wa what? (Score:4, Informative)
WRONG!! WRONG!! WRONG!!
You are confusing virtual (app) memory and physical memory.
Virtual memory is ALWAYS limited to 4GB (with 2/2GB or 3/1GB split of user/kernel) on 32-bit, PAE or not, Workstation or Server.
PAE allows for more than 4GB PHYSICAL memory. That means you could have 2 3GB apps running all in RAM (no swap) in 6+GB RAM.
For ONE app to use more than 4GB, you NEED 64-bit.
Each application page (usually 4K) is mapped to physical space, whether it's RAM or swap (when idle of course). The PAE allows you to map a page on more than 4GB RAM. This is done entirely by OS.
The problem is that drivers need to know the physical address, because that is what HW devices can access. Some drivers are poorly implemented and fail to do this (like giving a 32-bit address when they sould give 36-bit to the HW).
For a server, the company usually has an IT department that can get certified HW (not off-the-shelf cheap HW) and they usually test the server before deploying. So any driver issue can be corrected (either change the HW or resolve the driver issue) before deployment.
So MS did not want to get calls of data corruption and limited PAE on client windows. My problem (and the article's author's) is that WE (tech-savy computer users) cannot activate it afterwards.
PS: PAE was implemented since Pentium Pro. As I recall it already had 36-lines for adresses (that is 64GB memory space).
Re:Wa wa what? (Score:4, Informative)
The best source for info for this is likely Mark Russinovich. His blog is the origin of the "difficult to measure risk" quote.
Because device vendors now have to submit both 32-bit and 64-bit drivers to Microsoft's Windows Hardware Quality Laboratories (WHQL) to obtain a driver signing certificate, the majority of device drivers today can probably handle physical addresses above the 4GB line. However, 32-bit Windows will continue to ignore memory above it because there is still some difficult to measure risk, and OEMs are (or at least should be) moving to 64-bit Windows where it's not an issue.
He also acknowledges the commercial aspect of product differentiation on MS 64-bit OS versions, but suggests that the 32-bit issue derives from actual experience;
64-bit Windows client SKUs support different amounts of memory as a SKU-differentiating feature, with the low end being 512MB for Windows XP Starter to 128GB for Vista Ultimate and 192GB for Windows 7 Ultimate...
the Windows team started broadly testing Windows XP on systems with more than 4GB of memory. Windows XP SP2 also enabled Physical Address Extensions (PAE) support by default on hardware that implements no-execute memory because its required for Data Execution Prevention (DEP), but that also enables support for more than 4GB of memory.
What they found was that many of the systems would crash, hang, or become unbootable because some device drivers, commonly those for video and audio devices that are found typically on clients but not servers, were not programmed to expect physical addresses larger than 4GB. As a result, the drivers truncated such addresses, resulting in memory corruptions and corruption side effects.
http://blogs.technet.com/markrussinovich/archive/2008/07/21/3092070.aspx [technet.com]
I'd suggest though, the decision to completely disable PAE instead of only enabling it when paired with drivers certified by WHQL as being PAE-safe was a commercial one, based on SKU differentiation rather than risk.
Re:Wa wa what? (Score:4, Interesting)
So there's been a hardware based solution to this since the days of the Pentium Pro( early 90s ) and it is used by open source while Microsoft uses the 4GB limit as a tool to get people to pay up. Surprise, that's why Microsoft has so much of your money in their bank account. These kinds of things are old news but it always helps to let others know that in the open source world, these restrictions and/or features get worked around to improve the product instead of getting used to extract money.
LoB
Re:Wa wa what? (Score:4, Informative)
That's complete bullshit. If you purchased the 32 bit version of Vista, you can go on the Microsoft website and order the 64 bit version for a little more than the cost of shipping. Or you can just buy 64 bit to start with - there's no price difference between the 32 bit and 64 bit editions.
Re:Wa wa what? (Score:4, Insightful)
That's a completely different thing. He's referring to an incident where MS limited the number of inbound connections on port 80. They did that specifically to make it impossible for people to run large scale web-servers on NT Workstation. It had nothing to do with security/stability - it was purely an attempt to protect their profit margin.
And, btw, one of the first things I did after installing XP was get rid of that silly TCP/IP restriction. I agree that it was useful for at least slowing the transmission of worms, as well as limiting how effective they could be as part of a DDOS botnet attack, but I had the exact opposite experience from yours when it came to P2P apps.
I'm also fairly certain that you're wrong about it being "a simple reg entry". You actually had to patch TCPIP.SYS in order to remove/modify the connection limit.
Re: (Score:3, Insightful)
But the article seems to be about a licensing-based restriction on allowed physical memory, depending on your version of Windows. So even if Windows and your hardware supports PAE, it may not let you use >4GB RAM. (nb. PAE is potentially useful even if you don't have more than 4GB RAM, since it gets you the NX bit).
Re: (Score:3, Informative)
Personally I'd call it different versions of MS Windows but I think the above poster thought distributions was close enough.
Re: (Score:3, Informative)
Example of several Windows distributions:
Windows XP
Windows XP Media Center Edition
Windows Server 2003
Same cat, different skin.
Re:Wa wa what? (Score:5, Informative)
I have a feeling he hit it on the head when he mentioned third party drivers as being a possible reason for the limit.
Re:Wa wa what? (Score:5, Funny)
In fact, you can barrow someone's 64 bit disk ...
Barrow [wiktionary.org]:
A mound of earth and stones raised over a grave or graves.
Your plan to put 64 bit copies of Windows in the ground and cover them with grave stones and dirt intrigues me and I wish to subscribe to your newsletter.
Re:Wa wa what? (Score:5, Funny)
Re:Wa wa what? (Score:5, Funny)
I have added you to my newsletter as requested. Email confirmation should be received in 1-2 hours.
Mr. Brinestar, confirmation of E-mail confirmation received at 3:31 PM EST:
Subject: Subscription Confirmation for Binestar's newsletter that you requested on slashdot.
This is an automated email confirming your subscription to Binestar's newsletter as requested in your slashdot post here: http://tech.slashdot.org/comments.pl?sid=1347281&cid=29191073 [slashdot.org]
There is currently no way to remove yourself from this newsletter subscription. I hope you knew what you were doing when you subscribed!
Having completed reading your first newsletter (posted above), I found it vapid and devoid of the call to Microsoftalypse that I look for in all the periodicals I read (most notably my own newsletter entitled eldavojohn's Microsoftalypse that has a staggeringly high readership of a one eldavojohn of Slashdot.org).
Furthermore, to my horror, I noticed it was sent using an account from a hotmail.com address. Considering this datum, I found your footnote warning eerily apt. I shall post a scathing review of your newsletter (seven times longer than necessary) under the guise of frequent and unquestioned Slashdot contributor Bennett Haselton on the morrow. Good day, sir!
Re:Wa wa what? (Score:5, Funny)
Meh, us Linux users sneer at your pathetic Windows barrows. We put our stuff in SSH tunnels.
Demand curve pricing (Score:5, Interesting)
Just like that airplane seat, hotel room, rental car, theater ticket, etc... the same thing is sold for different prices according to willingness to pay. Just like senior discounts.
It's econ 101. demand curve pricing. if the demand versus price curve is actually curved with a long tale then maximum profit is achieved when a company is able to segregate consumers by willingness to pay. Your revenue is the are under the curve. and single price just gets the area of the larges rectangle you can place under the curve.
Econ 201: in second term economics we learn that the price demand curve is not actually a single curve but is a family of curves parameterized by the total number of units manufactured. So as the company is able to sell things at different prices to more people the entire curve shifts down, making it either cheaper for everyone, or mor profitable for the company depending who gets the benefit of the increased production.
even though it's galling to know the product you bought is just a dumbed down version of a beter one at no difference in manufacturing costs it may well be much cheaper than it would have been had they sold one thing at one price.
Of course it may be that your customers hate this. a few companies like Apple and Saturn use a more price fix model precisely because it fits their style of minimizing aggravation. But even they have college student or military discounts.
Re:Wa wa what? (Score:4, Informative)
Funny... What version of linux are you using that has the same limit? Slackware and Ubuntu don't have that limit.
Re:Wa wa what? (Score:5, Informative)
So is that the reason that Linux has the same limit?
Unless I'm misunderstanding you and the summary (not RTFAed yet - I know, I'm bad) Linux doesn't necessarily have the same limitation. The summary seems to imply that only 4GB of *physical* memory are being supported on 32-bit systems by some versions of Windows. All OSes running on 32-bit x86 are restricted to a 4GB virtual address space, therefore neither Linux nor Windows can offer more than 4GB of directly addressable memory *per process*. But many 32-bit x86 CPUs can address more than 4GB of physical memory using PAE mode.
The base requirement for using PAE is that the OS supports it - Windows can use it, Linux can too. PAE gets you the ability to address physical memory addresses over 4GB but only if the motherboard has enough address lines to actually relay these requests to the memory. Even if you can't / don't have more than 4GB of RAM installed, it may still be worth it because PAE also lets you use NX (no execute) on 32-bit. PAE on 32-bit doesn't make the process address space any larger, so any given process is still limited to 32-bit pointers.
32-bit Linux has to be compiled with or without PAE support, so your distro should make sure it installs a the right kernel version to correctly support your hardware. Some OSes (e.g. Solaris) can switch between PAE and non-PAE at boot time, so they only need one kernel image to support both modes. I don't know how Windows handles this.
A further benefit of PAE, that I've left till last because it's really somewhat gross: the memory mapped IO regions used by PCI devices also take up part of your physical address space. This can result in a "memory hole" where your *real* RAM is overshadowed by an area of memory-mapped IO regions - the real RAM is there but you can't access it. As a result, if you put 4GB of RAM in your system and use a non-PAE kernel (only 4GB of physical address space) then you are *guaranteed* not to be able to use all that RAM because you will *definitely* have hidden some of it "behind" the memory mapped IO regions. If you use PAE mode, the motherboard can potentially remap that "hidden" RAM to a higher physical address, so that you can use it. Not all motherboards support this remapping, even if they *do* support 4GB worth of DIMMs - which is rubbish because they're claiming to support memory that the hardware will never let you actually address. It pays to be wary of this kind of craziness - my mobo has this limitation, which I discovered after buying 4GB of DIMMs (so I stuck one in another PC, which kept me happy in the end).
Uh, sorry to the parent poster, I've rambled a bit off the point I was originally making and probably just told you a load of stuff you already knew!
Re:Wa wa what? (Score:5, Insightful)
Re:Wa wa what? (Score:4, Interesting)
Re: (Score:3, Funny)
Often would have done - but this time ;-) I thought of it roughly in the middle of the rest of my ramble. Maybe I'm just slow today!
Re: (Score:3, Interesting)
If you have an AGP video card you will not be able to access all the memory. AGP video is memory mapped just below the 4GB mark.
Re: (Score:3, Informative)
I thought the BIOS could just remap the rest of your RAM above 4GB, as shown in the article.
Re: (Score:3, Informative)
The last time I compiled linux for x386 I was given the option of supporting more than 4 gig of ram with a warning not to do it unless you needed to because of the performance penalty.
It seems like the cost effective thing to do in the vast majority of cases with x386 is to get multiple boxes with 4 gig of ram. The exception seems to be some database servers with a particular load pattern.
Re: (Score:3, Insightful)
The cost effective thing to do in the vast majority of cases is to upgrade to 64bit. Multiple 32bit machines will eat a lot more power.
Re: (Score:3, Informative)
I recently did configuration work on linux boxes that had 4 GB in RAM in them, but couldn't see more than 1GB of it because the previous administrator had neglected to enable CONFIG_HIGHMEM4G in the kernel configuration.
And to see more than 4GB of RAM on a Debian box, you need to use a special -bigmem kernel that has CONFIG_HIGHMEM64G enabled, because handling physical memory addresses more than 32-bits wide slows everything down, so Debian opted not to enable CONFIG_HIGHMEM64G by default.
So your Linux boxe
Re: (Score:3, Informative)
The Intel Xeon processors introduced a mode called PAE that increases pointer size to 36 bits. This allows the OS kernel to access more than 4GB of ram. Individual processes typically can not access this RAM directly but the OS and CPU handle this using hardware and virtual memory.
The Slashdot post is typically alarmist in claiming that there is an MS conspiracy afoot when in fact it's that PAE causes problems for countless drivers that are used on consumer computers but aren't used on servers. Servers h
Re: (Score:3, Insightful)
How can a 16 bit OS address 1 Meg of RAM when 2^16 is only 64k? Read the article. It's interesting.
Re: (Score:3, Funny)
If only they linked to an article that explains that~
dumbass.
Re: (Score:3, Informative)
Why run Vista32 on a 64 bit processor at all?
Windows Vista 64-bit ordinarily requires kernel-mode device drivers to be signed with a commercial Authenticode certificate. If you override this at startup, the desktop shows an ugly "Test Mode" banner in all four corners. There is a user-mode driver framework, but it makes no provision for input devices or a couple other cases. Some makers of low-volume hardware, such as hobbyists working on assistive input devices for people with disabilities or LPT-style bit-banging interfaces to systems too tiny/cheap/
Re: (Score:3, Insightful)
Two reasons I see for having a 32 bit OS:
1: 64 bit editions do not have 16 bit MS-DOS support. Of course, this can be mitigated by DOSBox, Windows XP Mode, and other VMs, but a number of places have a specific application that they want to work out of the box and not have to install/configure any more than they have to.
2: Netbooks have a low resource footprint. A 32 bit OS can work better in the 1-2GB max and still offer a workable machine.
Re: (Score:3, Insightful)