Who ate my memory?

The consumer versions of 32-bit Windows XP and Vista have a stated limit of 4 GB RAM, but a practical limit of about 3.1 GB. A lot of partial explanations have been floating around, so I thought I would try my hand at clearing up the issue. (Wish me luck!)

The design of the Intel 386 architecture supported access to up to 4 GB of physical memory (32-bit physical addresses) and unlimited virtual memory (4 GB at a time via 32-bit virtual addresses). 4 GB of physical memory seemed quite unthinkable at the time the chip was released, so the actual CPU did not have enough address pins to actually do this. Back then a 32-bit address space seemed extravagant for anything less than a supercomputer or mainframe. Nowadays, you can get 4 GB for under $400, and what was unthinkable in 1986 is within reach of anybody thinking about a new computer.

So at least I can access 4 GB, right? Nope.

The original IBM PC’s processor could access 1024 KB of physical address space, but you could only use 640 KB for RAM. The remaining 384 KB of address space was reserved for memory-mapped hardware and ROM. A similar situation exists with current systems: hardware reserves large chunks of the upper 1 GB of physical address space. Because of these reserved areas, a system with a 32-bit physical address space will be limited to somewhere around 3.1-3.5 GB of RAM.

To overcome the 32-bit limitation, recent x86 CPUs (Pentium Pro and later) have 36 address pins and can address 64 GB of RAM. The original design of the x86 32-bit protected mode only provided access to 32-bit addresses, so PAE (Physical Address Extensions) mode was created to allow access to 36-bit addresses.

PAE mode changes the layout of the page tables. Page tables map virtual addresses to physical addresses. Without PAE, the 32-bit virtual addresses map through 2 levels of page tables (1 level for huge pages) and are translated to 32-bit physical addresses. With PAE, the 32-bit virtual addresses map through 3 levels of page tables (2 levels for huge pages) and are translated to 64-bit physical addresses.

PAE doesn’t do anything to the virtual memory limit. Pointers are still 32 bits, so a process can only access 4 GB of address space at a time. However, using PAE, two or more processes could each access a different 4 GB of physical memory. With proper operating system support (i.e. AWE on Windows operating systems) PAE also allows a process to allocate additional memory outside its normal address space, then swap portions of that additional memory into its address space as needed.

So PAE is the answer, right? Well, maybe…

One thing that can prevent access to more than 4 GB of RAM is motherboard design. PAE can only access 64 GB of memory if all 36 address pins are properly wired up on the motherboard. This is not always the case, since those extra 4 wires make the motherboard just a little bit more expensive to design and manufacture (and use just a little bit more power). Many motherboards (especially on laptops) only have 32 address pins connected. If that is the case, no OS will be able to access more than 4 GB of address space.

Another hardware limitation is the ability of the chipset to remap RAM. If you have 4 GB of RAM, and 600 MB of address space is used up by PCI/AGP reserved areas, the only way to access the top 600 MB of RAM is to remap it into the addresses above the 4 GB boundary. Not all chipsets are able to do this, so some systems will just waste any RAM that happens to be shadowed by a PCI/AGP reserved region.

My BIOS reports 4 (or more) GB of RAM, I’ve enabled PAE, and I still only see 3.1 GB. What gives?

Unless you’re running one of the advanced server varieties of Windows, you won’t see more than 4 GB of physical memory. This is a limitation of Windows designed (I assume) to encourage people building expensive servers to pay more for Windows than those who are using it for normal day-to-day activities.

As for that last 0.9 GB, it all comes down to drivers and system stability. Not all drivers behave well in the presence of 64 bit physical addresses. Many driver authors assume that only the bottom 32 bits of the physical address are valid. Others don't properly handle the creation of bounce buffers when necessary (they’re needed when transferring data from a hardware device to/from a buffer that is above the 4 GB mark in physical memory).

Windows XP originally supported a full 4 GB of RAM. You would be limited to 3.1-3.5 GB without PAE, but if you enabled PAE on a 4 GB system with proper chipset and motherboard support, you would have access to the full 4 GB. As more people began to take advantage of this feature using commodity (read: cheapest product with the features I want) hardware, Microsoft noticed a new source of crashes and blue screens. These were traced to drivers failing to correctly handle 64-bit physical addresses. A decision was made to improve system stability at a cost of possibly wasting memory. XP SP2 introduced a change such that only the bottom 32 bits of physical memory will ever be used, even if that means some memory will not be used. (This is also the case with 32-bit editions of Vista.) While this is annoying to those who want that little bit of extra oomph, and while I would have liked a way to re-enable the memory “at my own risk”, this is probably the right decision for 99.9% of the general population of Windows users (and probably saves Dell millions in support costs). See the relevant KB article and a TechNet article for details.

Some of the server Operating Systems still allow the use of larger amounts of memory. I’m guessing that this is done with the assumption that higher quality parts will be used and drivers will be more likely to have been tested in PAE mode with large addresses.

Side-note: PAE is also related to page execution protection, called "hardware DEP" (Microsoft term), "NX" (AMD term), and "XD" (Intel term). In 32-bit x86 processors, this can only be used in PAE mode. This is why you might see PAE mode used even on systems with less than 4 GB of memory.

Performance note: 3-level page table lookups are inherently slower than 2-level page table lookups. However, the processor has substantial dedicated circuitry that usually eliminates most of the performance impact.

Comments (64)
  1. Thomas Schaaf says:

    Is there maybe a way to change this or would that conflict with the EULA somehow?

    And why doesn’t the 32 bit Version of Vista check whether the RAM is high quality enough or if it’s not?

    That way some users who would buy the high quality hardware would get support for the things they buy..

  2. Doug E. Cook says:

    I’m not sure what this has to do with the EULA. I haven’t looked at the source code, but from the KB articles I read, it seems like the 32-bit physical address limitation is built into the kernel. I don’t think there is any kind of registry setting that would remove the limitation. I could be wrong.

    This isn’t about RAM quality. This is about device driver quality. In many cases, the difference between cheap hardware and great hardware is not the hardware — it’s the quality and stability of the driver. Unfortunately, it is very difficult to determine whether a driver is well-written. WHQL is a good start.

  3. Shresel says:

    But how come, that Vista only shows 2GB of RAM, even with PAE enabled? BIOS reports 4GB, so VIST should say something like 3.1GB, right? Not 2.0GB.

  4. Nelson says:

    I also have DEP, and PAE as a result, enabled, and have 4 GB of ram that is detected correctly on my 64-bit system, but on my 32-bit it is not.

  5. Nelson says:

    Sorry, I meant to specify that I am only reading 2GB of ram in my 32-bit VISTA, not in the vacinity of 3 as others have done successfully.

  6. Doug E. Cook says:


    That’s weird. This sounds like a motherboard limitation or a motherboard driver issue, but I can only guess.

  7. Pavan says:

    Thanks for detailed information. But my PC has Intel 3.0 GH 4 Processor 631, with 1.5GB RAM. The physical memory shown properly in BIOS but in System properties of XP SP2, it shows 1.37GB RAM. Is it required to enable PAE here? I guess as its not more than 4GB, PAE setting is not required. Where is another .13G RAM?



  8. Yuhong Bao says:

    Shame on the driver writers that still write drivers that does not work with PAE!!! PAE support existed since Windows 2000!!!!!

  9. shippee says:

    I have read the above, and appreciate those who try to shed light on this situation.

    I have:



    Intel socket 775 processor (6400 @ 2.13 GHz)

    Windows Server 2003 Enterprise Edition with PAE enabled

        – and the /SOS switch in the BOOT.INI file

    MB shows 4096 GB upon boot

    Windows shows 4096 GB when booting with /sos switch

    Windows shows 4096 GB in properties

    BUT – Microsoft Virtual PC 2007 and Microsoft Virtual Server and other ‘utilities’ only show 2048 GB of available memory within the application(s) – so even though system shows me 4096 GB I’m thinking really only 2 GB is available for use because of PAE being enabled.  If I turn off PAE then I have a bit over 3 GB available.  What kind of a twist is this throwing into the explanations above, if any?

    Steven Shipee


  10. Brad says:

    To Pavan:

    You are not even close to the amount of memory that would require PAE.  Check to see if your system is using an on-board video chipset instead of a dedicated video card.  Usually when you see a chunk of memory missing in Windows like that, it’s because the system has reserved that memory for video memory, or something like that.  A quick calculation shows that your are missing about 128MB of memory, so that would make sense.  Your BIOS should have a setting for how much memory is reserved for video.

  11. Matthew says:

    We are having that problem with XP too. For me it’s really funny because I think the market will regulate it by itself. If the operatingsystem will support the hole 4 gb the manufactures will build better hardware ! But in that way you could compare the situation with buying a new car. You are buying a new ferrari but the dealer tells you that he switched the engine. It’s too dangerous an the chance that you’ll have an accident is too high…

    ‘ Nowadays, you can get 4 GB for under $400, and what was unthinkable in 1986 is within reach of anybody thinking about a new computer. ‘

    You’re right but microsoft just released vista, in that fact I’m really wondering that you solved it with that version. The memory is since the last years very cheap.

    Why don’t you relase a patch where you can switch between 3,1 gb and 4 gb ?

    Because of that all I become suspicious that microsoft isn’t able to fix it !

  12. you should have thought twice says:

    This is a joke. I mean, do you really believe this funny explanation?

    Did MS ever cared about crashes because of bad third party hardware when developing an OS?

    Did MS cared with DOS about this? No!

    Did MS cared with Windows 98 about this? No!

    Did MS cared with XP about this? No!

    And now suddenly you ignore t`he right of your costumers to decide themselves what to inatslland waht not by manipulating the the availablity of RAM in the OS?

    Tell this your grandma. Maybe she is believing this.

    We are on a free market. If the argumentation above woul be correct, nobofy would buy products with bad drivers anymore within 6 months. The producers of those bad drivers would reengineeer and everybody would be happy after 12 months. This is how life works. Everywhere.

    And no you (MS) has the balls to stat, that you want to protect the costumer by disallow to make his own decision? What is the next step? MS forbids to use dualcore because it might be incompatible with some drivers?

    How about Vista? Why did you not forbid Vista because it is incompatibel with so many drivers? Why did you not care there about your costumers? Maybe because the reason behind all this is a totally different one?

    Just sit down and think. This is so unlogic, We are not that dump! I am shocked that someone writes an article about this in the public.

  13. Intel Quad 6700 on ASUS P5B E Deluxe says:

    This is my issue: 4 Physical gig memory in this system. Running windows server 2003/SQL. Memory shown as 2.91 GB. Bios shown 3 BG total. When I updated bios to the latest still unable to get it to see  4BG in bios.

    Not I’ve tried 4 different motherboards same thing. So I’ve done ini file, pae,bios, not sure what’s going. Any suggestion? Thanks

  14. Adam says:

    I believe 64bit Windows Vista fixes this problem so I think the solution is to FINALLY move beyond 32-bit everything.  Driver manufactures and application developers need to focus on 64bit support Microsoft needs to encourage this through the removal of 32bit support on a determined schedule.  I believe they have already taken the first step towards doing this by only releasing Exchange 2007 in 64bit.  Excellent!

    Do I need more than 3GB of memory for Windows XP/Vista 32bit?… maybe it would be nice but I think I’ll move to 64bit and into the future and start taking my lumps now.    My 2 cents.



  15. butonic.de says:

    I lately got my hands on 4GB of RAM which I tried to put to use in my Laptop. My Fujitsu Siemens Celsius H240 is a Intel CoreDuo based Platform and I had hoped that I would be able to acess all of the memory. Long story short: the circuit / BIOS combinat

  16. Silvereagel says:

    Hi i  got the same problem here too i got 4gb RAm my bios confirms it but my Vista only uses 2 GB. any idea what i can do about it??

  17. Doug E. Cook says:

    Silvereagel – You can use Windows Server 2003 (you must enable PAE), or you can use a 64-bit operating system. You might also be able to access more memory by minimizing the hardware installed (each hardware component reserves some address space, possibly reducing the address space accessible to Windows).

  18. Silvereagel says:

    Im running vista 32.

    i know that the system cant take use of the full 4gb but. It only shows 2gb i meen i have readen alot of this and the most people can at least use 3.5gb or so.

  19. Doug E. Cook says:

    Silvereagel – I really don’t know. I have two video cards on my machine, so I can only access 3 GB. When I remove one of them, I can access 3.5 GB. It depends on the hardware you have installed. But I don’t know the exact reasons why it doesn’t work for you.

    Maybe your BIOS is configured to remap the memory and it is remapping too much of it. Normally the BIOS will only remap the part that conflicts with hardware. But Vista-32 can’t use any of the remapped memory (since it is remapped above the 4GB mark).

  20. No, si usas un sistema operativo de 32 bits no puedes usar más de 4 GiB de memoria RAM. Punto. Con 33 bits sólo puedes acceder a 2 elevado a 32 posibles direcciones. Existen mecanismos propuestos para tratar de acceder…

  21. Shiv says:

    Running Linux eliminates these problems.

  22. J says:

    Not true – Linux can’t re-wire your motherboard. Linux actually faces many of these same problems – the only difference being that Linux is happy to let you shoot yourself in the foot with driver quality issues with 64-bit addresses, where Windows will try to protect you. But this is only applicable if you motherboard and your chipset can support PAE, which a very large number can not.

  23. sol says:

    this article was referenced on slashdot on 22-DEC-2007:  http://hardware.slashdot.org/article.pl?sid=07/12/22/076211

  24. "Linux is happy to let you shoot yourself in the foot with driver quality issues with 64-bit addresses, where Windows will try to protect you."

    On Linux, drivers are free software.  If they have bugs, we fix them.  We don’t have to add workarounds to "protect" the user from 3rd party propietary trash.

  25. Patrick says:

    All you people missing 128 MB or 64 MB of RAM probably have on-board video.

    Intel and Pavan, this isn’t an issue of the OS not accessing that RAM — it’s just your style of MB.

  26. Yuhong Bao says:


  27. Matt says:

    "On Linux, drivers are free software.  If they have bugs, we fix them.  We don’t have to add workarounds to "protect" the user from 3rd party propietary trash."

    I agree with open-source development, however the word "protect" isn’t evil. Protection is good. The facebooking, myspacing, e-mailing, pornsurfing end user shouldn’t need to be aware of hardware configuration.

    1 bug on MS software = media fieldday

    100 bugs on Linux = another day at the office.

  28. Rico says:

    So this problem only arises, if using a 32bit architecture? or is this also a problem for 64bit architectures? I’m thinking of buying a new PC and wanted to have 4GB RAM in it (and be able to use this 4 GB).

  29. dman says:

    Do Mac (is this a dirty word?) users have these problems?

  30. Brandon says:

    I have a 64 bit prosseser and I’m looking fowerd to getting vista ultamate 64 bit.

  31. Jim says:

    Before I try this I thought I would ask a couple of questions (before we start…I am NO guru when it comes to computers, so bear with me please).

    1. I run Vista64 with a total of 8GB, shows 3.83GB. Total VM of 9.58Gb, shows 5.94GB.

    2. I’m trying to run Autodesk Inventor (32) and have a large assembly that "dumps" in the (roughly) 4GB area. I imagine I’m hitting the 4GB "limit".

    3. I’ve seen where adding /PAE will get me the full 4GB, but what about the other 4GB above that. Will I ever be able  to access the full 8GB with Inventor?

    Sorry for any "stupidity" on this, but I’m on a "non-supported" machine at the company I work for…so I’m the IT guy for this (and yes, we’re in trouble).


  32. Justin says:

    Mac users are shielded from these problems by not having infinitely varying hardware and software configurations.

    On hardware that doesn’t allow more than 4 GB of address space, Apple limits the RAM to a lower value, generally 2 GB. Higher-end machines with higher RAM capacity are designed with all the necessary hardware support included.

    The Mac OS X kernel and Unix layer have been 64-bit for a while, and Leopard (OS X 10.5) also offers full support for 64-bit applications with graphical user interfaces.

  33. I am running Windows Vista x64 and I installed 4GB of RAM, the BIOS shows 4096MB RAM but Windows Vista shows 3070MB RAM. This is seriously f*cked up.

  34. Doug E. Cook says:


    I’m not sure what numbers you’re quoting. If you’re running Vista64, Windows will support at least 8 GB (depends on which version of Vista) as long as your motherboard and BIOS also support that amount of memory. However, even using the 64-bit version of Vista, your 32-bit applications will never be able to access more than 4 GB of memory at once. /PAE is not applicable for 64-bit versions of Windows — it is an adjustment that only works with the 32-bit versions of Windows and helps the 32-bit versions overcome certain specific limitations of the 32-bit mode.


    Actually, the Mac OS X kernel is NOT 64 bit, though it can make use of more than 4 GB of memory via various tricks. Newer versions of Mac OS X can run 64-bit applications through a thunking layer (similar to the trick that the 64-bit version of Windows uses to run 32-bit applications on a 64-bit operating system). Other versions of Unix do have 64-bit kernels available, but Mac OS X does not yet have this technology implemented. Not to say that is necessarily a bad thing, as generally it is the application and not the kernel that benefits from the 64-bit support.

  35. Andrew says:


    I see exactly the same problem. I have just upgraded my laptop – now I have 2 x 2GB RAM. In BIOS I see 4GB, but on Vista 64 only 3GB.

  36. Hug says:

    Windows xp/vista 32bit can only use 2gb of memory unless you enable the /3gb in the boot.ini. It cannot utilize the memory. you want 4gb or more of ram you need to upgrade to 64bit windows.

  37. hug says:

    PS vista sucks not worth it. stick with xp until windows 7 comes out

  38. sss2 says:

    yeah my PC with 2 OS (Vista 32-bit and XP sp2) just detected 3,5GB PC 800 DDR2 but in my Bios detected 4 GB..

    how to fix it .. maybe vista 64-bit

  39. hug says:

    Yes, anything 64-bit It will read 3.5gb ram but it will still only use 2gb for the user regardless. unless you do the 3gb in the bootini but even taht can cause problems. 64bit is the way to go for up to 8gb of ram utilization

  40. Nick Panoussis says:

    Bottom line is that with 4 GB RAM, even if you get windows 64-bit versions, it can be a possibility (motherboard+bios combination limitation) that U  don’t get the entire 4GB RAM, is this correct?

  41. Doug E. Cook says:


    If you have a 64-bit edition of Windows but you still only get 3.5 GB of RAM, it is a motherboard or BIOS limitation (the motherboard is not remapping the memory). In some cases, this something that can be enabled in the BIOS options, but on laptops it is often simply a solid limit.


    Actually, the /3GB switch is much more complicated than that and has NO EFFECT on how much RAM can be used by Windows. Normally on a 32-bit operating system, Windows reserves 2 GB of address space for itself and gives each process 2 GB of address space. With the /3GB switch, Windows limits itself to 1 GB of address space and processes can use 3 GB of address space if they are specially marked as "large address aware". Note that this refers to address space, not RAM. Also note that this switch has a significant impact on many areas of the system (maximum amount of disk cache, maximum number of threads, windows, processes, TCP/IP sockets, etc.) since there is less space available for the operating system, so it should only be used to correct a specific problem where a memory-intensive program (SQL Server or Exchange) runs out of address space.

    I personally kind of like Vista, but there are definitely pros and cons. It is certainly more secure and a lot of things just work better, but it also uses more memory and can be a bit annoying. So I can understand your opinion.

  42. Ashraf says:

    Dear All,

    I have Installed 8GB of RAM (2GB each 4 Pcs) in windows XP Pro 32 bit, but it is showing only 3.5 GB.

    how can i enable the full 8 GB?

    please give me the simple way to do….

    send me to my email please….




    thank you in advance


  43. Ashraf says:

    Dear All,

    I have Installed 8GB of RAM (2GB each 4 Pcs) in windows XP Pro 32 bit, but it is showing only 3.5 GB.

    how can i enable the full 8 GB?

    please give me the simple way to do….

    send me to my email please….




    thank you in advance


  44. Erik says:

    There have been a number of comments regarding os x 10.5. In fact, os x leopard kernel is 32-bit, NOT 64-bit.

    Se for example:


  45. AlexM says:

    Okay I also have this problem.. Been running 2×1 gigs of ram for some time, and now upgraded with further 2×1 gigs.. BIOS detects 4 gigs but windows (xp pro) only 2.. Been playing a bit with the /PAE and /3gb switches with no result and can now understand that these are effectless in my case.

    dcook, you were explaining something about the /3gb switch, something about letting some programs use larger amounts of ram or adress space.. How to do this? Think that would solve my problem, as my music software demands at least 2 gigs of FREE memory!

  46. mingus says:

    Re J’s comment on Linux:

    Just for anyone coming across this page for info, J’s comment re Linux having this problem too is misleading.

    Of course if the hardware cannot support the memory addressing extension, no 32-bit OS can.  So obviously there is a mobo and chipset prerequisite.

    Having said that, since the 2.6 kernel, Linux 32-bit supports up the 64GB of addressable memory.  It is not necessary to use the 64-bit kernel, and there are no special driver requirements or issues using the 32-bit drivers.  Therefore, the remark re 64-bit address driver issues (which I assume back references the problem described with Windows drivers) is not only not applicable, it is uninformed (to put it kindly).

    The short of it is that this limitation is a MS design decision.  Specific to the desktop.  Period.  Don’t like it?  Go 64-bit or go Windows Server or go Mac or go Linux.

  47. SpizyChicken says:

    I’m running 2x2GB for a total of 4GB with Windows XP Pro SP2 32 BIT. Only showing 3.2GB of ram in windows, but shows the full 4GB in bios.  I would have gone with 64 bit but the main software I use for my business doesn’t support 64bit. BLAH!

    Intel Q6600 Quad

    4GB or XMS Ram (showing 3.2gb)

    2.5 TB hard drive space.

    1 TB RAID

    NVidia Quadro 1500 FX

  48. Sam says:


    I boot using Win PE.(64 Bit architecture)

    I have 64 Gb Ram but task manager shows 2GB of Ram only.

    Any proper explanation for this will be greatly appreciated.

    – Sam

  49. DanielEran says:

    AppleInsider has a good rundown on how Mac OS X and Windows compare (and a historical overview of memory addressing) in "Road to Mac OS X 10.6 Snow Leopard: 64-Bits" at:


  50. Doug E. Cook says:


    I took a quick look at the article. The Mac side was interesting, but I found the parts that contrasted the Mac with Windows to be quite narrow-minded and one-sided. I suppose that’s to be expected from the source, but I guess I shouldn’t have such high hopes.

    Windows is somehow bad because it either runs a 32-bit kernel (in which case it is limited to only 32-bit apps) or a 64-bit kernel (which has been around and working for several years now, and in which case it runs 64-bit apps in 64-bit mode and 32-bit apps in 32-bit mode). On the other hand, Mac is good because it either runs a 32-bit kernel (which can support 64-bit apps if running on 64-bit hardware) or a 64-bit kernel (which doesn’t actually exist yet, but when it does it will run 64-bit apps in 64-bit mode and 32-bit apps in 32-bit mode). There is, of course, some kind of layer between the kernel and the app in all cases, but somehow that is a bad thing for Windows and a good thing for Mac…

    I must be missing something here, because I don’t really see how the actual 64-bit functionality available from the Mac vs. Windows is really all that different in any meaningful way. There are a few differences in the approaches taken by MS and Apple, but both deliver approximately the same functionality — I can install an OS and run 64-bit apps (if the vendor has a 64-bit version available).

  51. bryan says:

    it sucks to even think that vista is good. I thought with a 32 bit im able to get all 4gb ram. But for nw, it does show 4gb with sp1 but then when I use powertools, its just showing 3gb. May I ask, what if i use xp, what will be the maximum limit of ram accepted?

  52. notten says:

    Half way through that article you decided to say 64-bit addresses instead of 36-bit. I found that amusing although not distracting from the quality of the content.

  53. Bikerman says:

    I run both 32 on one box and 64 ultimate on another, neither show 4 gigs but neither really seem to suffer a lack of performance more than any other super high-end desktop.

    And its not like I sit at one of our designer’s macs and want what he has, it’s all fast.

    Informative article nonetheless, now back to work!

  54. Thor Hundesson says:

    Running modern day games like GTAIV or Colin McRae Dirt (2) is virtually impossible with only a mere 2 GB RAM at hand….

    Once more the IT Industry is jackassing its clients who are stupid enough to pay alot 4dajunk…..

    Cheap excuses from incopetent developers who’ve been 2 tired to do a proper job and blaming the jacka….clients who refuse to be fooled even more with pricing from fantasialand….

    grrrmbl….how the f*** may i activate PAE ?

    Anyone tell me how to run new generation games on my brand new Acer Aspire M5641 ?

    Intel Core 2 Quad 6600 2.4GHz, 4GB RAM (hahaha…funny joke on the packaging…), NVIDIA Geforce 9600gs / 712-2500mb / Vista SP1 updated to the max + Windows ready boost enabled…

    Dont know anymore what to do….

    tnx 4 usable sugestions….

    PS. My next PC WILL be an APPLE you suckers from Macrojunk….

  55. Yours is one of the best pages I have found on this subject. Indeed, it’s one of the few that are commendable. But I have to ask why don’t you point out that the means to do:

     while I would have liked a way to re-enable the memory “at my own risk”, this is probably the right

     decision for 99.9% of the general population of Windows users

    exists anyway, through boot options? It’s not as if Microsoft would have had to do extra work for what you say you want. All that Microsoft would have needed to do is set pae=ForceDisable and truncatememory=0x100000000 as defaults at installation. Manufacturers who were confident of their hardware and drivers could remove these when setting up. Your 99.9% would be protected.

    Instead, 32-bit Vista retains the code for accessing memory above 4GB but the licensing mechanism is used so that memory above 4GB is discarded. If Microsoft were more open about this being the way the limit is imposed, then the limit might seem less disagreeable. At least it could then be discussed on the basis of what actually is done, and those driver and hardware issues could be assessed independently. Better yet, 64-bit Windows could be assessed on its merits as an operating system for the mass market, instead of being promoted misleadingly as being necessary for using 4GB and more of RAM.


  56. danny says:

    1. enable PAE in registry by changing the value from 0 to 1 ( it that has not already been done)

    Start—>Run—> type: regedit–>go to:

    HKEY_LOCAL_MACHINE/SYSTEM/CurrentControlSet/Control/Session Manager/Memory Management.

    Make a new DWORD and name it "PhysicalAddressExtension" and put it on"1".

    2.add a line in your boot.ini ending with "/3GB" for instance:

    multi(0)disk(0)rdisk(0)partition(1)WINDOWS="Microsoft Windows XP Professional" /noexecute=optin /fastdetect

    multi(0)disk(0)rdisk(0)partition(1)WINDOWS="Microsoft Windows XP Professional 3GB Switch" /noexecute=optin /fastdetect /3GB

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  58. sohbet says:

    I am running Windows Vista x64 and I installed 4GB of RAM, the BIOS shows 4096MB RAM but Windows Vista shows 3070MB RAM. This is seriously f*cked up.

  59. T. Roll says:

    Hahaha! It’s funny how every second comment seems to be the reincarnation of either:

    "BIOS shows 4 GB or RAM while Windows only shows 3.5 GB !!!!1 Halp me pl0x !!!1one!"


    "I ‘upgraded’ my PC/Laptop/Toaster to 1 Bazillion GB or RAM but it just won’t use more than 2/3/4 GB !!i!1!eleven!"

    Did you people even read the article? Sorry but if you keep posting the same questions over and over again, even though they were answered a hundred times already, then you are nothing but ignorant fools who shouldn’t be using (or at least building/upgrading) computers. You are simply not smart enough for that task, sorry.

  60. tekzalim says:

    Turkiyenin en kaliteli sesli chat sitesi.

  61. tekzalim says:

    Turkiyenin en kaliteli motosikletr sitesi.

  62. tekzalim says:

    Turkiyenin en kaliteli ruya tabir sitesi.

  63. tekzalim says:

    Turkiyenin en kaliteli kameralı chat sitesi.

  64. Roux says:

    Knowing this is an old thread, I'll risk having no answer…

    I understand that the OS Kernel/hardware/whatever will reserve space on my memory that will not be available to the rest of the applications, that is why I have 4GB or RAM but it shows only 3.

    Now the question I have is this: when my computer had only 2GB RAM (and we're talking about the same computer), Windows showed me the whole 2GB as available. Why did it not show me only 1GB (as I believe it should have because of the reserved space)?

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