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

  • Thread starter Thread starter Sarah White
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Sarah White

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:

http://support.microsoft.com/kb/283296

--snip--

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

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

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

--snip--

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!!!
 
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.

http://support.microsoft.com/?kbid&ID=929605
 
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
flawlessly.

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:

--snip--

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.

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

http://www.microsoft.com/whdc/system/platform/server/PAE/pae_os.mspx

--snip--

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

--snip--

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.
 
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.
Click to expand...



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

http://www.microsoft.com/whdc/system/platform/server/PAE/pae_os.mspx

--snip--

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
Click to expand...


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?
 
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.
 
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:

http://www.ocmodshop.com/ocmodshop.aspx?a=989

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.
 
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.

Sarah White said:
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:

http://www.ocmodshop.com/ocmodshop.aspx?a=989

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.

Mark said:
The point is:
If you don't have more than 4GB of memory, PAE will not change how
memory is reported.

It is supported, but only through BCEDIT:
Click to expand...
Click to expand...
 
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.
Sarah White said:
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:

http://www.ocmodshop.com/ocmodshop.aspx?a=989

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.

Mark said:
The point is:
If you don't have more than 4GB of memory, PAE will not change how
memory is reported.

It is supported, but only through BCEDIT:
Click to expand...
Click to expand...
 
Let's try one more time, but I'll just give instructions:

From elevated cmd prompt:
bcdedit /set PAE forceenable
Reboot

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
Reboot

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
Reboot

If it still doesn't work, it's not supported by your machine.
 
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?)
-- http://msdn.microsoft.com/en-us/library/ms791485.aspx

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
 
pacinitaly said:
Has anyone tried this?

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

" *BCDEdit /set PAE forceenable* " enable use of 4GB RAM
" *BCDEdit /deletevalue PAE* " disable ability to see 4GB RAM
Click to expand...

Windows desktop OS's only use PAE to enable DEP. The address windowing
extensions aren't enabled except in Windows server OS's.
 
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