4gb RAM installed and working showing 3gb useable on XP

[Guest]

Checked KB and this forum, nothing useful. 4gb in 4 sticks working on startup
and memory check. All sticks checked ok and all swap configurations done.
Only 3gb showing in XP pro system and task manager performance. 3gb switch
set in boot and working for applications at 2.701mb. SP2. Latest bios level,
server MB supports 6gb.

 

[Rock]

Checked KB and this forum, nothing useful. 4gb in 4 sticks working on startup
and memory check. All sticks checked ok and all swap configurations done.
Only 3gb showing in XP pro system and task manager performance. 3gb switch
set in boot and working for applications at 2.701mb. SP2. Latest bios level,
server MB supports 6gb.

That's normal. XP has a 4GB address space but programs can only access
3 GB if the /3GB switch is set.

 

[Guest]

Sorry, did not answer the question. XP sees only 3gb with 4 gb installed.

 

[Rock]

Sorry, did not answer the question. XP sees only 3gb with 4 gb installed.

:

And that's all it will show.

 

[Kerry Brown]

Sorry, did not answer the question. XP sees only 3gb with 4 gb
installed.

It did answer the question Windows XP can see 4 GB of memory space.
Unfortunately it cannot use 4 GB of RAM. Some of the address space is
reserved for other purposes. If you hunt around you can find tweaks to get
around 3.25 GB. Any more you'll have to get the 64 bit version.

Kerry

 

[Jim]

It did answer the question Windows XP can see 4 GB of memory space.
Unfortunately it cannot use 4 GB of RAM. Some of the address space is
reserved for other purposes. If you hunt around you can find tweaks to get
around 3.25 GB. Any more you'll have to get the 64 bit version.

Kerry

This is not exactly the case. The remaining 1 or 2 GB are used to map the
OS into the user space. So, in fact the extra space is far from unused.
Jim

 

[Richard Urban]

This is not exactly the case. The remaining 1 or 2 GB are used to map the
OS into the user space. So, in fact the extra space is far from unused.
Jim

That sure sounds like "reserved for other purposes" to me!


--


Regards,

Richard Urban
Microsoft MVP Windows Shell/User

Quote from George Ankner:
If you knew as much as you think you know,
You would realize that you don't know what you thought you knew!

 

[Tim Slattery]

Checked KB and this forum, nothing useful. 4gb in 4 sticks working on startup
and memory check. All sticks checked ok and all swap configurations done.
Only 3gb showing in XP pro system and task manager performance. 3gb switch
set in boot and working for applications at 2.701mb. SP2. Latest bios level,
server MB supports 6gb.

Check this article:
http://support.microsoft.com/default.aspx?scid=kb;en-us;888137

 

[Guest]

Thank you, the article was helpful although it pushed my expertise. I seems
like SP2 is causing the low reading. It was not clear if the memory is being
used and not reported by sys properties or just ignored. The condition of
4gb or more was met but /pae was not. We have SP2 but not /pae in boot.ini.
We do not understand why with 2gb, 2gb is reported. With 4gb, 3gb is
reported, although it may be that some drivers act differently with 4gb and
SP2 changes the reporting to avoid a compatibility issue. Since we are not
running PAE, I am not sure why we have the problem.

 

[Mak]

read this too: http://forums.2cpu.com/showthread.php?t=63004&page=1&pp=30

 

[Kerry Brown]

read this too:
http://forums.2cpu.com/showthread.php?t=63004&page=1&pp=30

Thanks for the interesting link. Reading through it, it seems no one except
some programmers at Microsoft really understands how Windows works with
large amounts of ram. My personal experience shows little or no speed gains
even with large video or graphics files above 2 GB. Once you hit 2 GB the
speed of other components like the hard drive controller and the drives
themselves become much more significant. Although closely related Server
2003 does show better performance with 4 GB than 2 GB. After reading the
thread you linked to this may just be because of the better motherboards
it's usually installed on. Maybe using a server board that supports PAE with
XP would show some improved performance with XP and 4 GB. It would be an
interesting experiment. Has anyone tried it?

Kerry

 

[Guest]

Sounds I should leave well enough alone. 3gb it is. In reality 4gb may be used
a little but maybe not in some ways possibly.

 

[Bob Huntley]

Please forgive me if this is a silly question.

If XP has a 4GB address space, does that mean that there is no benefit in
setting a memory pool (RAM + Virtual Memory Size Allocation) that is larger
than 4GB?

Reason I am asking is that I recently upgraded to 2 GB of RAM, and wonder if
the normally quoted rules for sizing Virtual Memory (e.g. "never smaller
than the RAM size", "1.5 * RAM size" etc etc) are still valid for large RAM
sizes.

Bob,

 

[Rock]

Please forgive me if this is a silly question.

If XP has a 4GB address space, does that mean that there is no benefit in
setting a memory pool (RAM + Virtual Memory Size Allocation) that is larger
than 4GB?

Reason I am asking is that I recently upgraded to 2 GB of RAM, and wonder if
the normally quoted rules for sizing Virtual Memory (e.g. "never smaller
than the RAM size", "1.5 * RAM size" etc etc) are still valid for large RAM
sizes.

Bob,

That rule of thumb doesn't apply in XP. The size of the page file
needed depends on your computing habits and programs running. In
general more ram needs less page file, not more. What you need to do is
run a little utility from the link below and monitor page file use.
Then set it accordingly. This is an excellent article about virtual
memory and page file setting by the late Alex Nichol, MVP.

http://aumha.org/win5/a/xpvm.htm

 

[Tim Slattery]

Please forgive me if this is a silly question.

If XP has a 4GB address space, does that mean that there is no benefit in
setting a memory pool (RAM + Virtual Memory Size Allocation) that is larger
than 4GB?

No, it doesn't mean that. XP can address 4GB of physical RAM. Each
process that runs in the OS is allocated a virtual memory space of
4GB. 2GB of that is reserved for the OS, so each process can use 2GB
of virtual memory. Few processes will use the entire 2GB, but you may
have 20-30 processes running in your machine, all using hundreds of MB
of memory.

XP manages both physical RAM and the swap file on disk to make every
process think it has as much RAM as it needs, and to try to keep the
data that each process uses most in RAM as much as possible. The best
thing to do with the swap file is to let Windows manage it.