Does Vista 32-bit see 4GB of memory as 4GB?

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Nocturnal

Nocturnal

Lifer
Jan 8, 2002
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Say if you view the My Computer property dialog, does it say 4GB of memory? Or, is it similar to XP where often times it only reports 3.25 or 3.5GB of memory being available?
 
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Steve

Lifer
May 2, 2004
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www.chicagopipeband.com
It's a 32-bit OS, like XP and 2000. It will show you whatever RAM is available. Whatever isn't has its address space in use by the system (hardware addressing, etc.).
 
Nothinman

Nothinman

Elite Member
Sep 14, 2001
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3.25
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That number is completely arbitrary, the amount of memory 32-bit XP and Vista will see is determined by your hardware and can be much lower than 3.25 if you've got lots of greedy hardware.

It's a 32-bit OS
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That's irrelevant, it can't see the memory because MS designed it that way. The fact that 32-bit Win2K3 Server can access memory >4G is proof of that.
 
S

Steve

Lifer
May 2, 2004
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www.chicagopipeband.com
We've had this discussion before, Nothinman. That's basically a 36-bit OS:

Text

"This 36-bit memory space allows Windows Server 2003, Enterprise Edition and Windows Server 2003, Datacenter Edition to support 32 GB and 64 GB of physical memory, respectively, by using Physical Address Extensions (PAEs). However, the use of PAEs imposes a significant overhead, requires programmers to use the Address Windowing Extensions (AWE) application programming interface (API), and still limits the maximum physical memory to 64 GB. It also does nothing to change the 4 GB of virtual memory address space."
 
Nothinman

Nothinman

Elite Member
Sep 14, 2001
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We've had this discussion before, Nothinman. That's basically a 36-bit OS:
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Then XP and Vista are 36-bit OSes because they support PAE, MS just limited them to 4G for driver compatibility reasons. But I really doubt anyone is going to start calling 32-bit CPUs or OSes 36-bit because it's not really correct and all of the parts that matter are still 32-bit.
 
Nothinman

Nothinman

Elite Member
Sep 14, 2001
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OSX sees 4GB well and its 32 bit...
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Well first the hardware is handled differently so the same driver issues won't apply to OS X that apply to Windows so it's possible that Apple didn't feel the need to limit OS X like MS did with Windows. And second the kernel of OS X has been 64-bit for a release or two even though the userspace is still mostly 32-bit and that's what determines how much memory is seen.
 
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aka1nas

Diamond Member
Aug 30, 2001
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Vista 32-bit has the same limitations as XP with regard to usable RAM and for the same reasons. There's too many crappy drivers around for consumer applications and hardware that there would be probems.
 
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tcsenter

Lifer
Sep 7, 2001
18,684
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Originally posted by: Nothinman
We've had this discussion before, Nothinman. That's basically a 36-bit OS:
Click to expand...

Then XP and Vista are 36-bit OSes because they support PAE, MS just limited them to 4G for driver compatibility reasons. But I really doubt anyone is going to start calling 32-bit CPUs or OSes 36-bit because it's not really correct and all of the parts that matter are still 32-bit.
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PAE only enables the OS to give user-mode processes (e.g. applications) access to physical memory above the 4GB boundary when more than (not equal to) 4GB physical memory is installed. It has no bearing on the 4GB virtual addressing space limitation.

Access to memory above the 4GB boundary in PAE mode must use the much slower paged-access mode because it cannot be accessed via DMA.
 
Nothinman

Nothinman

Elite Member
Sep 14, 2001
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PAE only enables the OS to give user-mode processes (e.g. applications) access to physical memory above the 4GB boundary when more than (not equal to) 4GB physical memory is installed. It has no bearing on the 4GB virtual addressing space limitation.
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I know this and that's what we're talking about, the amount of physical memory the OS allows you to use and 32-bit XP and Vista only let you see a max of 4G minus hardware resources.

Access to memory above the 4GB boundary in PAE mode must use the much slower paged-access mode because it cannot be accessed via DMA.
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I doubt I'd call it much slower and it's only inaccessible to devices that only have 32-bit BARs.
 
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tboo

Diamond Member
Jun 25, 2000
7,626
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I have 4gb of RAM. With 1 8800GTX installed on my PC I see 2.75gb of RAM. With a dual SLI setup of 2 8800 GTXs I see 2.25mb of RAM
 
zephyrprime

zephyrprime

Diamond Member
Feb 18, 2001
7,512
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The reason why windows xp sees only 3.25 GB of memory on a 4GB machine is because of video memory mapping. The video memory on your video card is getting mapped onto the cpu's memory space multiple times (once for monitor 1, once for monitor 2, once of tv out).
 
Nothinman

Nothinman

Elite Member
Sep 14, 2001
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The reason why windows xp sees only 3.25 GB of memory on a 4GB machine is because of video memory mapping. The video memory on your video card is getting mapped onto the cpu's memory space multiple times (once for monitor 1, once for monitor 2, once of tv out).
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Partially true, but there are also more devices that need memory ranges and AFAIK each device only gets mapped once. If your 3x numbers were correct then an 8800 with 768M of memory would use over 2G worth of addresses.
 
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russki

Senior member
Nov 7, 2000
640
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I have 4 gb on my work maching and winXP says I have 3.5GB NOT 3.25GB... I run dual monitor 256mb quadro card for my CAD stuff
 
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masteraleph

Senior member
Oct 20, 2002
363
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Originally posted by: asdfqwertyuiop
is it possible to use the last 1gb somehow with vista 32? Any 3rd-party program?
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No. MS could allow it, via PAE, but there are various things (i.e. nvidia drivers) that will auto-crash with more than 4GB combined address space and memory in a 32-bit windows system. This would be what is known in the industry as a "bad thing."
 
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jlbenedict

Banned
Jul 10, 2005
3,724
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Originally posted by: asdfqwertyuiop
is it possible to use the last 1gb somehow with vista 32? Any 3rd-party program?
Click to expand...


Yep.. its called "using an operating system designed to see and use more than 4gb"

:p
 
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