OOM Error

#2
Hi Folks

All 32 bit operating systems (WinXP and Vista32) have 4 GBs of Virtual Address Space
Is the above correct for XP ?

From what I can find, only XP Professional supports 4GB VAS.

HTH
ATB
Paul
 

n4gix

Resource contributor
#3
Is the above correct for XP ?

From what I can find, only XP Professional supports 4GB VAS.
Paul, that came directly from an official MS document that I read while researching for this article. Unfortunately, I didn't think to maintain a list of references, so can't provide a URL to that MS document at this time...

However, keep in mind that the range of integer values that can be stored in 32 bits is 0 through 4,294,967,295 or −2,147,483,648 through 2,147,483,647 using two's complement encoding. Hence, a processor with 32-bit memory addresses can directly access 4 GB of byte-addressable memory.

Because of this, the maximum size for a VAS table is likewise limited to 4GB, half of which is allocated for the OS + peripherial devices, unless otherwise re-allocated through use of the /3GB switch, and having an application marked as LARGE_ADDRESS_AWARE.
 

n4gix

Resource contributor
#5
In the below cited article, note that for every 32bit OS version, these limits to VAS apply:

User-mode virtual address space for each 32-bit process

2 GB
Up to 3 GB with IMAGE_FILE_LARGE_ADDRESS_AWARE and 4GT
Please refer to the table for max RAM for every OS version. Note that in the table for WinXP, the only version without 4 GB is the Windows XP Starter Edition, with a maximum of 512 MB

http://msdn.microsoft.com/en-us/library/aa366778(VS.85).aspx

From the above, it would appear that the reported 3.5 limit applies only to the maximum size of the "User-mode virtual address space." The remaining physical RAM however is still usable by the OS to map the "Kernel-mode virtual address space."

Also, take special note of Phil's second paragraph, first sentence:

Normal Win32 processes have 2G of address space, out of the 4G available. The remaining 2G is left to the OS for its needs, drivers, etc. This is completely independent of physical RAM - this is how much virtual address space each process gets.
 

n4gix

Resource contributor
#7
MSDN - 4-Gigabyte Tuning states 4GT is only available on XP Professional.
Since I actually have three systems running WinXP Home Edition, and have successfully used "...the BCDEdit /set command to set the increaseuserva boot entry option to a value between 2048 (2 GB) and 3072 (3 GB)..."

...I have conclude that they are flat wrong in that article... :yikes:

It certainly wouldn't be the first time... :rotfl:

Keep in mind these are the same folks who maintain that one cannot network WinXP Home systems...

...while I've happily networked 3 WinXP Home 'puters, 2 Vista32 'puters and most lately a Win7x4 'puter...

Phil Taylor once remarked that "there's a great deal of confusion..." What many don't seem to realize is that a large amount of the "confusion" is mostly MS generated, with their KB articles that contradict each other...
 
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#8
Hi FOlks

Bill -
Agreed, lots of conflicting info on MSDN & KBs. :D



Since I actually have three systems running WinXP Home Edition,
and have successfully used "...the BCDEdit /set command
to set the increaseuserva boot entry option
to a value between 2048 (2 GB) and 3072 (3 GB)..."
Not disputing your above,
nor that the boot.ini can be edited to include the switches. :D

My question is -
Does XP Home Edition actually do anything with them ?
i.e.
What difference(s) are you seeing in XP Home Edition ?



PS
Isn't BCDEdit a Vista only tool ?
Equivalent on XP Pro is bootcfg.
Or notepad for XP Home Edition.



Keep in mind these are the same folks
who maintain that one cannot network WinXP Home systems...
Never seen MS make such claims. :D

You've always been able to setup a workgroup
but never join a domain from XP Home Edition.

Lots of articles at - MSDN Search - XP Home Edition network



HTH
ATB
Paul
 
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n4gix

Resource contributor
#9
Not disputing your above,
nor that the boot.ini can be edited to include the switches. :D

My question is -
Does XP Home Edition actually do anything with them ?
i.e.
What difference(s) are you seeing in XP Home Edition ?
What difference(s)?

Before applying the /3GB switch and increasing userva via the boot.ini file, frequent and repeatable OOM Errors...

...post application, zero OOM Errors after several hundred hours of testing on all three WinXP Home Edition machines.

I've also reversed the process and reverted all three machines to default condition, with the OOM Errors returning with a vengence, so I'm very confident that it isn't merely a placebo effect.

I'm a pragmatist Paul. If it works for me (as it has also worked for others running WinXP Home Edition), then I have to accept the results as valid, licit and successful, irrespective of the claim to the contrary by MS... :coffee:

Regarding the BCDEdit remark, it is indeed a Vista tool. That's the problem with being tired and simply copy/pasting a quoted remark from somewhere else... :tongue-ti
 
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