Physical Address Extension (PAE) does not work on vista as expected.

Discussion in 'Windows Vista Performance' started by Sarah White, Jun 8, 2008.

  1. Sarah White

    Sarah White Guest

    I upgraded (a so-called "clean install" on same partition... it made xp
    pro x64 unusable by renaming various system folders) to windows vista
    home basic hoping that PAE would work.

    I had assumed that 4GB RAM would be no problem (the intel e6600 core2duo
    in this system supports 64bit instructions, and as a result PAE works on
    linux just fine) though it is not doing what I expected.

    After installing Vista SP1 (came out recently) from windows update, I
    decided to try using BCDEDIT.EXE and set PAE to "force enable" mode...
    Not working as expected!!!

    Well, pressing [windows logo key on keyboard] and [break] at the same
    time (you can also bring that up by right clicking what XP called "my
    computer" and selecting "properties") ... windows now reports: Memory
    (RAM) 4.0 GB ... it was too good to be true:


    Article ID : 283296
    Last Review : February 28, 2007
    Revision : 4.4

    """ Windows Server 2003 Enterprise Edition loads a standard VGA video
    driver for NVidia... """

    • Microsoft Windows Server 2003, Enterprise Edition (32-bit x86)
    • Microsoft Windows Server 2003, Datacenter Edition (32-bit x86)


    Wrong on two counts!!!

    A) I'm using nvidia's latest WHQL drivers

    Windows is not using "standard VGA video driver" but is using Nvidia's
    latest digitally signed vista 32 bit drivers (Version 175.16) Digital
    Signer: Microsoft Windows Hardware Compatibility

    B) I'm running windows vista (with signed, WHQL drivers) and windows
    task manager still reports "physical memory (MB) 2813" on the
    performance tab!!!
    Sarah White, Jun 8, 2008
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  2. Sarah White

    Mark H Guest

    If you are running a 32-bit version of Windows Vista on a computer that has
    4 GB of memory installed, the amount of RAM available for use could be less
    than what you would expect. For more information about memory usage, see
    article Q929605, in the Microsoft Knowledge Base.
    Mark H, Jun 9, 2008
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  3. Sarah White

    Sarah White Guest

    Err... obviously :p

    Yes, 32bit addressing has a 4GB limit. That's the whole point of PAE. I
    suppose I should have asked "what are the steps required for using PAE
    to actually remap addressing to the extended areas?"

    Based on the behavior I am seeing, I'm inferring that my video card
    drivers aren't detecting PAE (and / or realizing my cpu supports 64 bit
    instructions) and as a result, the driver's DMA / MMIO (or whatever
    technical jargon applies here) is falling back on non-PAE mode and using
    addresses inside the 32-bit RAM area.

    I'm outright frustrated that when I "upgraded" my 3 year old edition of
    Windows XP Pro x64 (2005 edition) to Windows Vista Home (32bit, and SP1
    is brand new) that enabling PAE is no more successful than it was in XP.
    I could understand if the drivers weren't digitally signed / WHQL
    certified, or if the hardware was not capable of 64bit mode, but these
    drivers are digitally signed, and the drivers for XP Pro x64 worked

    Any rate, yesterday I invoked the "windows anytime upgrade" feature in
    windows, paid a bit of money and such. In the next few weeks I'll be
    receiving vista "ultimate"... I'll once again opt-in / elect to join the
    "Help Experience Improvement program".

    ....I already felt it neccessary to submitted a comment about vista's
    built-in "help and support" definition of PAE:


    Physical address expansion (PAE)

    A feature that allows x86-based computers to support more than 4
    gigabytes (GB) of physical memory. Up to 64 GB of physical memory can be
    used as regular 4-kilobyte (KB) pages, and the number of bits that can
    be used by the kernel to address physical memory can be expanded from 32
    to 36.

    Sarah White, Jun 9, 2008
  4. Sarah White

    Sarah White Guest

    Oh nuts, looks like yet another microsoft article (this one explains PAE
    in depth) failed to list "windows vista" as officially supporting PAE.


    Windows and PAE Windows Version Support

    Windows 2000 Professional / Windows XP
    AWE API and 4 GB of physical RAM

    Windows XP SP2 and later
    AWE API and 4 GB of physical address space

    Windows 2000 Server / Windows Server 2003, Standard Edition
    AWE API and 4 GB of RAM

    Windows Server 2003 SP1, Standard Edition
    AWE API and 4 GB of physical address space

    Windows Server 2003, Enterprise Edition
    8 processors and 32 GB RAM

    Windows Server 2003 SP1, Enterprise Edition
    8 processors and 64 GB RAM

    Windows 2000 Advanced Server
    8 processors and 8 GB RAM

    Windows 2000 Datacenter Server
    32 processors and 32 GB RAM (support for 64 GB was not offered because
    of a lack of systems for testing)

    Windows Server 2003, Datacenter Edition
    32 processors and 64 GB RAM

    Windows Server 2003 SP1, Datacenter Edition
    32 processors and 128 GB RAM


    There was one particular thing I found annoying on this gaming system I
    built a couple years ago -- I had to run all my games in "32bit
    emulation mode" under x64 version of windows if I wanted to use all my
    ram; Here I am a couple years (and a few upgrades) later, and I'm still
    unable to tap into all of that ram even with an upgraded version of windows.
    Sarah White, Jun 9, 2008
  5. Sarah White

    Al Dykes Guest

    PAE required hardware on the mobo and it's been a while since I used
    PAE but then, it wasn't available on desktop mobos.

    It's possible it is standard on any 64 mot mobo, if that's the case
    I'd like to hear that from someone.

    If you don't know what PAE does, it probably won't do you any good.

    Again, my info is a little dated, but the application had to be
    programmed for it. Things like Oracle and Windows Server were.
    W2K/Pro wasn't.

    I've heard conflicting things about Photoshop using PAE.
    Al Dykes, Jun 9, 2008
  6. Sarah White

    Al Dykes Guest

    Thank you. I didn't know that.

    What is the practical use if, in this case, it doesn't let the box
    access more than 4GB compared to 3.5GB without ity, and it does have
    overhead when it is being used?
    Al Dykes, Jun 9, 2008
  7. Sarah White

    Sarah White Guest

    Oh, it's VERY practical. The addressing requirements of my hardware eats
    over a gigabyte (frighteningly close to half) of my 4GB RAM. If you run
    multiple instances of games at a time (very common practice for MMORPG
    gamers) your memory requirements go up dramatically.

    I might as well mention: you can actually use OVER 4GB of ram with
    PAE... I just happen to only have 4GB installed at the moment. Of
    course, I won't be upgrading my ram until I have bullet-proof PAE
    support in the OS that's most compatible with my games.
    Sarah White, Jun 9, 2008
  8. Sarah White

    Mark H Guest

    Mark H, Jun 9, 2008
  9. Sarah White

    Mark H Guest

    Mark H, Jun 9, 2008
  10. Sarah White

    Sarah White Guest

    I'm amazed that you're bothering to tell me that; my original post (top
    of this thread) said that I used BCDEDIT to enable PAE.

    As for changing "how memory is reported" I have two conflicting reports.

    Report 1) Control Panel\System: 4.0GB (2.75GB before BCDEDIT -> PAE)
    Report 2) Task manager "performance tab" (Physical Memory) Total 2813MB

    If you're saying style-2 (task manager or other) reports won't be
    changed by PAE, are you able to cite / reference a specific article? I'm
    curious if this is because my signed, WHQL drivers are trying to use the
    same address as a large portion of my RAM, or if some entirely
    unexplained thing is going on.

    As for style 1, I hate to break it to you, but control panel -> system
    (easily opened using [win] + [break] keys) is reporting a different
    (higher) number now that I'm using PAE: it actually says 4.0 GB now!

    Thanks, good idea for providing that link explaining BCDEDIT under the
    new windows bootloader. I personally found it a bit confusing (was very
    much accustom to using boot.ini) Personally, I like the abbreviated info
    (even though it isn't official) that I found here:

    Note: I'm quite confused about the terms "nx" bit and "hot add" memory
    and a few other terms in there. I know there was a reference in my bios
    menu for something that might have been the "nx" bit... Some kind of
    security feature under the same screenfull of settings that had
    virtualization, disable core 1 (only use core 0) and CPU throttling.
    Sarah White, Jun 10, 2008
  11. Sarah White

    Mark Guest

    Well, my goal was not to frustrate you more or make you upset with me.

    My first post simply pointed out that there may be a difference in reported
    memory depending on where you look: e.g. System Property may report 4GB, but
    task manager may report less.
    I didn't refer to BCEDIT until you replied with: "I suppose I should have
    asked "what are the steps required for using PAE to actually remap
    addressing to the extended areas?"

    To that, I sent you to the instruction manual.
    Have a nice day.

    Mark, Jun 10, 2008
  12. Sarah White

    JW Guest

    Only server OS systems can support more then 4GB of memory with a 32bit OS
    since the use memory mapping to provide 4GB of logical memory to different
    running process which map to different physical memory addresses.
    Vista 32 bit like most if not all personnel computer Boss can not address
    more then 4GB since it does not use memory mapping.
    JW, Jun 10, 2008
  13. Sarah White

    Mark H Guest

    Let's try one more time, but I'll just give instructions:

    From elevated cmd prompt:
    bcdedit /set PAE forceenable

    The reboot is required before proceeding.
    Most likely, not all RAM is being reported.
    That's because on 32-bit OS, DEP is required when PAE is running. (Even
    if not supported.)
    DEP may cause other problems.

    From elevated cmd prompt:
    bcdedit /set nx AlwaysOff
    bcdedit /set PAE forceenable

    It is proven that PAE and Creative sound cards won't work together.
    There may be other configurations that don't work.

    To turn off:
    From elevated cmd prompt:
    bcedit /set nx AlwaysOn
    bcedit /set PAE default

    If it still doesn't work, it's not supported by your machine.
    Mark H, Jun 10, 2008
  14. Sarah White

    Sarah White Guest

    I upgraded WinXP Pro x64 partition to vista because... let me think...
    Sure, 4GB was nice, but practically ZERO driver support for XP Pro x64

    As for your comment about "Only server OS systems..."

    I suppose it is known that the limit is 4gb on XP (why though?)

    The 4GB limit is really just OS developers being lazy (or greedy?)
    Truly, PAE / NUMA / 4GB limit is far more reliable on linux (lol)
    .... What do I know; I'm just a developer that has vista for gaming.

    My opinion, greed -- the 64 bit OS is unnecessary to access 4GB or more
    of memory, but then you are EMULATING 32bit mode for gaming and other
    apps. My very first thought was to check vista's "help and support" ...

    1) go to your start menu and open "help and support" in windows vista.
    2) type "PAE" in the search
    3) the only result is "Physical address expansion (PAE) (definition)"

    They even admit / explain it's "up to 64 GB" but didn't mention they
    will deny you access to your ram / hold out and sell you "upgraded"
    64bit version of windows to make an extra buck. Just my $0.02
    Sarah White, Jun 22, 2008
  15. Sarah White

    pacinitaly Guest

    Has anyone tried this

    Type what's between the " " in a CMD prompt as admi

    " *BCDEdit /set PAE forceenable* " enable use of 4GB RA
    " *BCDEdit /deletevalue PAE* " disable ability to see 4GB RA
    pacinitaly, Mar 30, 2009
  16. Sarah White

    pacinitaly Guest

    have you read the thread

    answer: so you can see the full 4GB of ra
    pacinitaly, Mar 30, 2009
  17. Sarah White

    Kerry Brown Guest

    Windows desktop OS's only use PAE to enable DEP. The address windowing
    extensions aren't enabled except in Windows server OS's.
    Kerry Brown, Mar 31, 2009
  18. Sarah White

    pacinitaly Guest

    WOW, good to know, glad I set it back to defaul
    pacinitaly, Mar 31, 2009
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