locked
max addressable memory for vista beta 2 RRS feed

  • Question

  • I'm trying to find whether Vista is capable of supporting 4GB of memory..not having any luck looking through the requirement documents.  I would be installing it on a laptop with an Intel Core Duo and Intel 945GM Express chipset.  The laptop specs and Intel specs say max is 4GB but I've been told XP Pro can't address that full amount unless it's a 64-bit processor.

    Thx

    Sunday, June 11, 2006 5:50 PM

Answers

  • The following quote from a Microsoft white paper regarding running 32-bit applications on a 64-bit Windows XP Professional system may help clarify the issue at hand:

    "The primary driver compatibility concern is running Physical Address Extension (PAE) mode on 32-bit systems. PAE mode enables processors to address greater than 4 gigabytes (GB) of memory. The primary difference between PAE memory paging and non-PAE memory paging schemes is the extra level of paging that is required in PAE mode (3 levels instead of 2)."

    In other words, the limit of non-PAE memory paging schemes in 32-bit systems is 4GB. 64 bit versions of the XP operating system can use up to 128GB of RAM, depending on the version. 64 bit versions of the Windows Server 2003 operating system can use up to 1 terabyte of RAM, depending on the version.

    Regarding whether an application can take advantage of more than 2GB of RAM, I can't speak to that directly. Since I don't have more than 2GB of RAM anywhere, I can't try to configure applications to use greater than that amount. :) However, if you are talking about a single application, that's a question for the ISV. The limitation of 2GB of RAM is not in the operating system.

    A caveat: Not all of the SKU details are available yet for the different versions of Vista that will be sold, so I can't say for certain that lower-end versions of the OS won't have memory limits.

    Hope that helps!

    Wednesday, June 14, 2006 3:47 AM

All replies

  • Windows XP Pro 32-bit has an upper limit of 4GB.

    Windows XP Pro 64-bit has an upper limit of 128GB.

    Does your laptop currently have 4GB of RAM installed and the OS is not recognizing all of it, or is this a planning question?

    Monday, June 12, 2006 10:25 PM
  • Hi Saska,

    Just bought a toshiba laptop with 1gb memory installed but it can go to 4gb max.  It's got the Intel Core Duo cpu with the Intel 945GM Chipset.  It's currently running XP Pro..was scouting around for 2gb memory sticks for it..they are hard to find at this point..anyway someone in another forum remarked why try since Windows/Vista would not be able to use the entire 4 unless it was the 64 bit version.  From what I've read in other discussions, this is not true correct?  However same discussions also stated that many apps don't/can't address more than 2gb unless designed to do to and few are.  I do plan to be using virtual server on this laptop so I'll need all the ram I can stuff in there..

    Wednesday, June 14, 2006 2:06 AM
  • The following quote from a Microsoft white paper regarding running 32-bit applications on a 64-bit Windows XP Professional system may help clarify the issue at hand:

    "The primary driver compatibility concern is running Physical Address Extension (PAE) mode on 32-bit systems. PAE mode enables processors to address greater than 4 gigabytes (GB) of memory. The primary difference between PAE memory paging and non-PAE memory paging schemes is the extra level of paging that is required in PAE mode (3 levels instead of 2)."

    In other words, the limit of non-PAE memory paging schemes in 32-bit systems is 4GB. 64 bit versions of the XP operating system can use up to 128GB of RAM, depending on the version. 64 bit versions of the Windows Server 2003 operating system can use up to 1 terabyte of RAM, depending on the version.

    Regarding whether an application can take advantage of more than 2GB of RAM, I can't speak to that directly. Since I don't have more than 2GB of RAM anywhere, I can't try to configure applications to use greater than that amount. :) However, if you are talking about a single application, that's a question for the ISV. The limitation of 2GB of RAM is not in the operating system.

    A caveat: Not all of the SKU details are available yet for the different versions of Vista that will be sold, so I can't say for certain that lower-end versions of the OS won't have memory limits.

    Hope that helps!

    Wednesday, June 14, 2006 3:47 AM
  • Saska,

    Thanks for finding that info, it helps..it's a bit of a minefield out there right now, for instance the top HP laptops only go to 2gb max vs the toshibas 4gb max.  So which should I buy?  Which will better serve me 3 years down the road?  On the surface of course is more is better.  But some are arguing that while 4gb may be attractive, buffing it out to a full 4gb ($$) is a waste of money in that the 32 bit apps can't / don't use anything above the 1st two GB's..it can devolve into technical mish-mash when all the end consumer wants to know is will the $ spent on that extra 2gb stick of ram be wasted? 

    Other posts I've seen generally agree the OS is not an issue, the apps have to be specifically developed to address above the 2GB limit, and most currently don't as there's not been a real need to.  But it also brings up other questions, say if I have two apps each needing 1.5 GB, will they have to share the first 2GB or can they each grab above that if needed (minus what the OS needs of course). 

    Appreciate your help!

    Wednesday, June 14, 2006 4:56 PM
  • Since the operating system is in charge of overall memory management for applications, I would conclude that a limitation of 2GB of memory use per application would not mean anything like "just the first 2GB available on the physical hardware". The application may only be able to take advantage of that (for example, maybe a 3D rendering program could only store 2GB of data buffered in RAM), but the other 2GB not in use by that application would be managed by the OS and used by other apps.
    Wednesday, June 14, 2006 7:14 PM
  • so how do i get vista to see all 4 gbs? it only shows 2.87 gbs of physical memory. i have 4 - 1 gig sticks that are matching pairs.  thanks for any help.
    Wednesday, July 19, 2006 1:57 AM
  • I guess I am in the same boat.

    I'm having trouble getting 32-bit Vista to recognize all of the RAM in my Shuttle SD37P2 "Conroe" (Intel 975X / ICH7R chipset) system:

    A clean install of 32-bit Vista RC1 (build 5600) only recognizes 2GB of RAM on a 4GB Shuttle "SD37P2" system.

    A clean install of 64-bit Vista RC1 (build 5600) on the same iron recognizes the entire 4GB of RAM.

    The Shuttle SD37P2 has the latest available BIOS SD37S022, dated 2006/07/06, an Intel Core-2-Duo E6700 processor, Intel 975X / ICH7R chipset and 4GB of ECC DDR2 RAM (as 4 sticks of 1GB each) The BIOS recognizes all 4GB of RAM in dual-channel mode and displays the correct RAM size in SETUP.

    The Shuttle BIOS has a setting for a "memory-hole" - which does NOT affect the amount of RAM seen by 32-bit Vista - setting it to "enabled" or "disabled" seems to have no effect on the result.

    I would rather run the 32-bit version at least for the near term as most of my 3rd-party software won't run on 64-bit.

    Any suggestions or ideas welcome! 8-)

    Tuesday, September 19, 2006 4:06 AM
  • Jesus Christ, 1 Terabyte!! I could run my entier system and backup all my filles in RAM and have it save state with my ups, I cant imagine ever needing more RAM or bits, procs mabey...
    Tuesday, September 19, 2006 6:52 PM
  • No - you are wrong. Windows XP Pro 32-bit has an upper limit of 3GB. I've got 4GB on my computer and Windows XP Pro 32-bit version only addresses 3GB. You're a MSFT employee and don't know this? Dang...glad you're not a technician in our company.

    The question I'm trying to find on MSFT's website is what Vista's upper limit going to be. It's like this company doesn't get it yet...we've got these monster machines out here and they (MSFT) are still holding up back from taking advantage of the PC power that's out here.

    DOS was dead years ago folks. It took you long enough to get rid of the 640K limit, now can you open the channel and let us have unrestricted access to what available hardware is on the market? It's not the hardware manufacturerers - it is MSFT that's keeping us down.
    Wednesday, October 25, 2006 3:30 AM
  • I have a similar problem as gmoffitt

    I have an older processor 3.4 GHz 478-pin w/ 1MB L2. Vista shows just about 3GB (2.99896), but I have 4GB of RAM.

    I thought Vista was going to fix the addressing issue...as I understand the CPU has the ability to map 36-bit...so my other devices would not "steal" address space.

    BTW...I haven't tried disconnecting all my PCI devices to see if the RAM increases...(a suggestion I saw for XP dated in 2005).

    I've seen some stuff about PAE and /3G, but I'm not sure if I can benifit from them. I'm not using this machine as a server and I can see almost 3GB so???

    ----

    Anyway, I just bought this DDR along with a 7800GS, so I don't want to have to purchase a new MOBO, VC and CPU 64....b/c then I'll just want DDR2.

    Monday, October 30, 2006 12:19 AM
  • As several folks above, I picked up an early EM64T H/T machine from early 2005 and tricked it out to the 4 gig memory limit. I tried the 3G and PAE Boot.Ini switches (and played with swap space, and tried Vista RC2 both 32 and 64 bit, and tried Fedora) w/o success after seeing only 3 gig showing (all 4 gig show in the BIOS). A gentleman elsewhere pointed to

    h20331.www2.hp.com/Hpsub/downloads/RAM%20Allocation%20w-WinXP_HP%20MWP%20x64%2003Nov05.doc

    which explains the issue quite well. Please note the above article is from HP but the issue really applies to the Intel chipset as far as I can understand... with no apparent "fix" if you want to keep BIOS and PCI working :( The above mentioned gentleman did mention picking up a patch that improved (reduced the loss) from the Intel site but did not specify the precise location. 

    Also, please note the Intel Core 2 Duos appear to have the same problem - from the December 2006 Macworld page 34 - "... the Intel chip set that Apple uses in the IMac allows the operating system to address only 3GB of RAM at a time -- and in total. So even if you put 4GB of RAM (split between 2GB DIMMs) in the IMac, the computer would still function as though it had only 3GB."

     

    Sunday, November 5, 2006 3:12 PM
  • that is not entirely true... i have an older Dell Precision 530 at home with dual 2.8GHz Xeon processors and 4GB of installed RIMMs, and Windows XP Pro picks it up as 3.58GB of memory.
    Monday, December 11, 2006 9:27 PM
  • with out getting into the tech aspect of it becuase i dont have a lot of time your 32 bit v of windows will allow "UP TO" 4 gigs the thing thatl imits your os from reading that full 4 gigs is the memory adress limation in a 32 os, everyhting u use in your system (Hardware) has its own memory adress.

      to put it simply the less hardware you have in your system the more usable ram u will see for exampl go int0 your bios and disable everyhting you are not using and take out all the hardware u have exept what u need to run your system barbone and you will get close to the 4 gig mark veryhting else u add will take a memory adress away from your ram and assign it to another peice of hardware. u have to stop thinking ram for a min and start thinking  adress's on a 64 bit os you wont have this problem as it has far more momory alocation adress slots.

     google what i am saying for more in depth explaination hope this helped a bit wish i had more time to explain further ill try and post more later if i can

    Tuesday, December 26, 2006 9:54 PM
  • This was well stated by enigmatai. Further details can be read here: http://www.brianmadden.com/content/content.asp?ID=69 

    Like my well stated friend said, stop thinking RAM and think TOTAL memory in a system. All 32 bit systems can only address about 4 gig of total memory period. Easiest thought is your video card. Mine is a 512, therefore my system immediatly can only handle maybe 3.5 gig then you must account for other system memory, as well as other hardware that requires address space. Even forget Windows, any 32 bit operating system can only address about 4 gig of Memory.

    Also note that PAE does move the divide of ram from an even split for application and kernal memory to allow more ram to be available for applications. Again read the linked article.
    Wednesday, January 31, 2007 3:17 AM
  • "All 32 bit systems can only address about 4 gig of total memory period."

    This shows a common confusion between virtual and physical address space.

    A "32 bit" CPU is a CPU with a 32-bit virtual address size. The virtual address space is thus 4GB.

    Since the Pentium Pro in the mid 1990s, the 32-bit Intel x86 architecture has supported a 36-bit physical address bus.  Therefore, a 32-bit (virtual) system can address 64GB (physical), given appropriate motherboard and chipset.

    From the point of view of the OS, the important feature is whether or not it enables Physical Address Extension (PAE) in the CPU control registers. Prior to XP SP2, the desktop OSes chose not to enable PAE, so the system effectively functioned with a 32-bit physical address space, and thus the RAM limit was somewhat less than 4GB.

    But with recent Intel processors, the OS needs to enable PAE to get hardware DEP (Data Execution Prevention) support. Therefore, on the fact of it, there's no reason why XP cannot support a true 4GB of RAM (i.e., extend the physical space slightly beyond the 32-bit physical boundary).

    Anyone know why the OS chooses not to do that?


    Thursday, February 8, 2007 1:03 AM
  • Thanks for this information.  I just installed an extra 1gig stick in my Vista 32 system for a total of 3 gig.  Vista only recognizes 2 gig.

    Running XP on the same machine, XP recognizes all 3 gig.

    Having read the article that you referenced, I'm wondering if it matters that I have 3 gig when running Vista.  If I take the new 1 gig stick out of Vista, will it still show 2 gig?  Or, will it recognize less than 2 gig?  Should I keep all 3 gig in the system?

    Saturday, February 10, 2007 7:42 PM
  • intel core duo is EM64T (64BIT by Intel) so you could put 4gb ram in and vista will pick it up, and 64bit is pretty useful in my opinion due to the performance and the fact you can gett 64 bit software when people bouther to make it (but who am i to say this im a software programmer lol)

     

    32 bit vista should pick up 4gb ram as a MAXIMUM amount, it can only address a maximum of 4GB ram

    Wednesday, February 21, 2007 12:00 PM
  • I have a new Dell w/ 4GB of RAM + e6700 duo.  Windows Vista Ulimate reports 3GB of RAM on the System Info (welcome) screen.

    This page explains it (somewhat):
    http://msdn2.microsoft.com/en-us/library/aa906211.aspx

    "increaseuserva Megabytes
    Specifies the amount of memory, in megabytes, for user-mode virtual address space. This variable can have any value between 2048 (2 GB) and 3072 (3 GB) megabytes in decimal notation. Windows uses the remaining address space (4 GB minus the specified amount) as its kernel-mode address space. "

    In other words - the system can only use 3GB MAX of application space (what the system info screen reports).   The other 1GB is used by the KERNEL for drivers, etc.

    Microsoft & Dell need to do a much better job of explaining this to people or there are going to be a lot of disgruntled customers out there, Especially after RAM prices come down and make 4GB more affordable.

    - LC
    Cyber Sprocket Labs
    http://www.cybersprocket.com/

    Tuesday, February 27, 2007 11:33 PM
  • AMD 3800+, 4 gig RAM, 2 x 250 gig SATA II HD; WinXP Professional, SP2; I would love for XP to recognize 4 gigs RAM; my BIOS does, but XP only sees 3 gig's. How can I improve XP's vision so it'll see and be able to use all 4 gigs RAM
    Monday, April 16, 2007 1:29 AM
  •  CharlestonSW.com wrote:

    I have a new Dell w/ 4GB of RAM + e6700 duo. Windows Vista Ulimate reports 3GB of RAM on the System Info (welcome) screen.

    This page explains it (somewhat):
    http://msdn2.microsoft.com/en-us/library/aa906211.aspx

    "increaseuserva Megabytes
    Specifies the amount of memory, in megabytes, for user-mode virtual address space. This variable can have any value between 2048 (2 GB) and 3072 (3 GB) megabytes in decimal notation. Windows uses the remaining address space (4 GB minus the specified amount) as its kernel-mode address space. "

    In other words - the system can only use 3GB MAX of application space (what the system info screen reports). The other 1GB is used by the KERNEL for drivers, etc.

    Microsoft & Dell need to do a much better job of explaining this to people or there are going to be a lot of disgruntled customers out there, Especially after RAM prices come down and make 4GB more affordable.

    - LC
    Cyber Sprocket Labs
    http://www.cybersprocket.com/


    Um... You bought that excuse? Its a known issue.. Check this thread..

    http://forums.microsoft.com/TechNet/ShowPost.aspx?PostID=1292561&SiteID=17

    Why would the system which uses the ram for drivers and kernel regardless of 3 or 4 gb max report the full 3gb and not 2gb when you have only 3gb physical mem installed? Is the system not using ram for those functions until you hit 4gb of physical ram? I doubt it... Why would they INTENTIONALLY make it mis-report ram after decades of reporting correct values (with the exception of shared video ram). I say BS! FIX IT!!
    Wednesday, April 25, 2007 5:36 PM
  • Hi,

    I have been told that XP pro only supports 3gb of ram, as in you can put 4 in but programs will only recognise 3. Is this the case?

    Thanks for your help

    Monday, June 4, 2007 10:55 AM
  • Hi Guys

    Dont meant to bust your bubble but memory limitations in windows is common and has no bairing to 32 and 64 bit.

    AMD and intel have a difference ie AMD 64bit processors and Intel use 32bit processors hence you have more than 1 version of vista and I dont meant vista home/ business/ ultimate I mean you have 32 bit which support intel and 64 bit which support AMD processors however that is all irrelevant this is to do with DEP (Data Execution Prevent) If you know how to configure this you can tell windows be Vista or XP to recognise all your RAM providing your BIOS recognises it too for Example :

    My BIOS detects 4gb RAM

    Windows Vista Ultimate 32bit Detects 3.4GB the same would happen to Windos Vista Ultimate 64bit. I know have both Smile

     

    The Answer is in DEP. I hope this links helps:

    http://support.microsoft.com/default.aspx/kb/912923

     

    also

    What is Data Execution Prevention?

    Data Execution Prevention (DEP) is a security feature that can help prevent damage to your computer from viruses and other security threats. Harmful programs can try to attack Windows by attempting to run (also known as execute) code from system memory locations reserved for Windows and other authorized programs. These types of attacks can harm your programs and files.

    DEP can help protect your computer by monitoring your programs to make sure that they use system memory safely. If DEP notices a program on your computer using memory incorrectly, it closes the program and notifies you.

     

     

    Check out MS knowledge base this will help you get your answers

    good luck as I am about to resolve my memory issues on Vista

    Friday, July 20, 2007 8:47 PM
  • hi
    the AMF Clicker changed name to Clicker Mouse Bar and it is free now.
    i am owner of the Clicker Mouse Bar program now [I got the source code] but I need a programmer [C or C++] to develop it some more for free. please help me.

    go to http://myhead1967.tripod.com/cd1/id26.html
    to contract me, go to http://myhead1967.tripod.com/cd1/id3.html

    carlo
    Friday, August 3, 2007 12:47 AM
  • Looks like we need to run Vista with the /execute option to disable DEP.

    But the question remains - HOW?

     

    Vista doesnt use boot.ini anymore!

    Tuesday, August 7, 2007 6:31 PM
  • Does Win XP Pro require a firmware or any other modification/update to utilize the 4 gig of RAM?

    Thanks
    Sunday, August 12, 2007 12:13 AM
  • No, YOU are wrong, Mensanot - just because your PC shows 3GB when you have 4GB installed does not define what the 'upper limit' is.  The upper limit is defined as the possible positions in physical RAM which have a unique address - mathmatically, the limit is 4GB in ANY 32bit OS (not just Windows, so you can drop the 'it is MSFT that's keeping us down' bit too).

     

    Windows XP and Vista report 3GB because the last 1GB is being used for kernal mode operations - 3GB for you, 1GB for the system.

     

    And I'm glad I'm not a technician at your company too - I'd hate to spend my entire day working with people who think they're always right.

     

    Monday, October 1, 2007 2:11 PM
  • I know what you say is true that 32 bit is limited to 4 gig's, and 64 bit's limit is 128 gig's. I would like to know if in the near future that something will be done to improve the limitions. I guess I'm asking for your fore sight into the future. One other point, have you seen a motherboard that can have 128 gig's of RAM. I've only seen MB's that only go up to 8 gigs. I'm typing and think at the same time. Can anything be done to the BIOS, and Vista to make corections? What I am seeing so far is that we have hit the glass ceiling  when it comes to increasing the useable RAM, either it be 32 bit, or 64 bit. Well that's my two cents.

    Saturday, November 3, 2007 9:04 PM
  • The limit on a 64 bit processor is well above 128 GB.  On a 64 bit processor, there are up to 17,179,869,184 GB addressable memory addresses. 

     

    Addressable memory (from a hardware perspective) is 2 raised to the number of bits.  2 raised to the 32nd power is 4294967296 byes or 4 GB.  2 raised to the 64th power is 18,446,744,073,710,000,000 bytes (or 17,179,869,184 GB).  Of course that is the physical upper limit.  It is up to the operating system to take advantage of it.

    Wednesday, November 7, 2007 1:03 PM
  • What someone quoted from earlier...The bit about being able to use between 2056 - 30xx amount of ram...  That's from info on how to increase your individual program size basically.  The max limit of a given process is inherently 2gb, you can change that to 3gb, or anywhere inbetween by following the instructions on that page.

     

    However that has nothing to do with whether your windows 32-bit (2000, xp, vista) OS recognizes 4gb of ram.  You'd do better to pretend you never saw that message as it has nothing to do with your question. 

     

    You can use up to 4gb of ram in your 32-bit system.  The issue you run in to is address space...  You have 4gb of total address space usable by your 32-bit system.  All of your hardware in your system uses up address space, as does your virtual memory etc.  Typically most hardware uses up the last bits of your address space.  Because that address space is used up (regardless of its actual size...which varies in every machine, since no machine has exactly the same hardware really), your total ram is minus the address space that is taken up by your hardware.  For instance, i have 4gb in my machine now, but with the hardware i have in it, i can only get access to around 3.4 gb of the ram.  If i take that ram out and put it in another one of my machines here, it has about 2.9 gb of ram available to the system.  I think, depending on what gpu you're using, it makes a pretty large impact on how much system ram you have available to your system.

     

    Now whats odd to me, is that when i'm running XP 64, with 4gb of ram installed, I only have 3.5gb of ram available to the system.  I should have all the address space i need for the system to allocate address space to my hardware above the 4gb mark.  ><...Which probably means my bios needs to be updated.  Dell ftw...

    Friday, November 30, 2007 3:16 PM
  •  

    Wow... that was a totally useless post.
    Thursday, December 13, 2007 12:11 AM
  •  GeChaos wrote:

    Hi Guys

    Dont meant to bust your bubble but memory limitations in windows is common and has no bairing to 32 and 64 bit.

    AMD and intel have a difference ie AMD 64bit processors and Intel use 32bit processors hence you have more than 1 version of vista and I dont meant vista home/ business/ ultimate I mean you have 32 bit which support intel and 64 bit which support AMD processors however that is all irrelevant this is to do with DEP (Data Execution Prevent) If you know how to configure this you can tell windows be Vista or XP to recognise all your RAM providing your BIOS recognises it too for Example :

    My BIOS detects 4gb RAM

    Windows Vista Ultimate 32bit Detects 3.4GB the same would happen to Windos Vista Ultimate 64bit. I know have both

     

    The Answer is in DEP. I hope this links helps:

    http://support.microsoft.com/default.aspx/kb/912923

     

    also

    What is Data Execution Prevention?

    Data Execution Prevention (DEP) is a security feature that can help prevent damage to your computer from viruses and other security threats. Harmful programs can try to attack Windows by attempting to run (also known as execute) code from system memory locations reserved for Windows and other authorized programs. These types of attacks can harm your programs and files.

    DEP can help protect your computer by monitoring your programs to make sure that they use system memory safely. If DEP notices a program on your computer using memory incorrectly, it closes the program and notifies you.

     

     

    Check out MS knowledge base this will help you get your answers

    good luck as I am about to resolve my memory issues on Vista

     

    Sorry to burst your bubble! But it appears are you are a complete idiot.

     

    http://msdn2.microsoft.com/en-us/library/aa366778.aspx#physical_memory_limits_windows_vista

     

    Enjoy the read and the new found understandings of the differences between 32bit and 64bit. Perhaps your experiences are caused because you bought AMD.

    Sunday, January 6, 2008 4:27 AM
  •  dave____ wrote:
    "All 32 bit systems can only address about 4 gig of total memory period."

    This shows a common confusion between virtual and physical address space.

    A "32 bit" CPU is a CPU with a 32-bit virtual address size. The virtual address space is thus 4GB.

    Since the Pentium Pro in the mid 1990s, the 32-bit Intel x86 architecture has supported a 36-bit physical address bus.  Therefore, a 32-bit (virtual) system can address 64GB (physical), given appropriate motherboard and chipset.

    From the point of view of the OS, the important feature is whether or not it enables Physical Address Extension (PAE) in the CPU control registers. Prior to XP SP2, the desktop OSes chose not to enable PAE, so the system effectively functioned with a 32-bit physical address space, and thus the RAM limit was somewhat less than 4GB.

    But with recent Intel processors, the OS needs to enable PAE to get hardware DEP (Data Execution Prevention) support. Therefore, on the fact of it, there's no reason why XP cannot support a true 4GB of RAM (i.e., extend the physical space slightly beyond the 32-bit physical boundary).

    Anyone know why the OS chooses not to do that?

    I know this is a very old post, but I'm still curious about Dave's question.

    Monday, July 21, 2008 3:10 AM
  • Reason is this:
    Enabling PAE also requires that all of your drivers (as well as many system utilities - AV and disc-burning apps, for example) are PAE-aware.  If they're not, at some point, they'll try to address a space that they don't think is possible, which equals driver crash, which equals OS crash.
    You're more than welcome to enable PAE in your boot file; however, how well it works is up to your hardware vendors.
    Typically, you won't often (if at all) find PAE-aware drivers for the desktop versions of Windows.  Server, yes; desktop, no.

    Monday, July 21, 2008 3:57 AM
  • The max limit is 4gb on XP 32...

    Your personal hardware limit may be 3.5GB, 3, 2.5, or 2...depending on how much hardware you have taking up towards the end of that limit.  Your hardware takes up address space too, it just starts from the 4gb mark and makes its way down.  Every different configuration will use a different amount.

     

    If you have 4gb+ on a 64 bit system, you (the motherboard) can map the address space for your hardware to a different area.  IE if your using XP, and the max of XP 64 is 128gb, it starts at 128gb and works its way down.  I really doubt it maps it that high, but it might.  So as an example (however unlikely...) you had 128gb of ram in your system, you'd be missing the last 2gb or so, depending on your hardware, and in Windows, would only show 126gb or 126.5 or 127...or whatever.

     

    Same deal with Vista.
    Monday, July 21, 2008 3:14 PM
  •  cuppie wrote:

    Reason is this:
    Enabling PAE also requires that all of your drivers (as well as many system utilities - AV and disc-burning apps, for example) are PAE-aware.  If they're not, at some point, they'll try to address a space that they don't think is possible, which equals driver crash, which equals OS crash.
    You're more than welcome to enable PAE in your boot file; however, how well it works is up to your hardware vendors.
    Typically, you won't often (if at all) find PAE-aware drivers for the desktop versions of Windows.  Server, yes; desktop, no.

    Thank you Smile

    Monday, July 21, 2008 11:47 PM