Windows XP and 4Gb or RAM

[Guest]

We just got a new box with 4Gb of RAM and dual core 2.8 processors. A very
nice piece of machinery. However, we are using XP 32 bit platform on a 64
bit chip and it is not recognizing all 4Gb of RAM. Do we need to upgrade the
OS to 2003 Advanced Server or the 64 bit XP platform?

 

[kenny]

yes you have to upgrade, but even if you do, it is VERY hard to utilize that
much ram with normal applications. The only way I could think of was to use
several virtual machines simultaneously.

 

[Rich Elgin]

Yes you need an OS that supports 64bit addressing.
With 32bit addressing you can only address 4GB. All of systems adapters
like Video cards need an address range to use it's memory. Address space
is assigned from the high end going downward during the BIOS and System
start up.
The address space used up by the adapters can not be used for the system
memory. That is why you can't use all of your 4GB of memory in a 32bit
OS system.
Rich

 

[Tim Slattery]

We just got a new box with 4Gb of RAM and dual core 2.8 processors. A very
nice piece of machinery. However, we are using XP 32 bit platform on a 64
bit chip and it is not recognizing all 4Gb of RAM. Do we need to upgrade the
OS to 2003 Advanced Server or the 64 bit XP platform?

There have been several threads on this issue recently. One theory is
that the PCI bus takes some address space, allocated from the top
down, so you aren't aware of it unless you're trying to use a full 4GB
of RAM.

Whatever, it certainly seems to be the case that if you put in 4GB of
RAM, WinXP will report somewhat less than that, and the amount of
"missing" RAM varies.

 

[Bob I]

Read this for the explanation
http://download.microsoft.com/download/e/b/a/eba1050f-a31d-436b-9281-92cdfeae4b45/mem-mgmt.doc

 

[Guest]

Thank you Tim. The interesting thing is that we booted the machine to a copy
of Kubuntu Linux live cd 64 bit and it recognized all 4Gb of RAM. The 32 bit
version Knoppix only saw the 2.75 the same as the 32 bit version of XP.
So, this makes me curious about the 32 bit XP.

 

[Tim Slattery]

Read this for the explanation
http://download.microsoft.com/download/e/b/a/eba1050f-a31d-436b-9281-92cdfeae4b45/mem-mgmt.doc

THANK YOU!! That's an excellent document! And the fourth paragraph on
page 10 has the answer to the question:

<QUOTE>
The physical address space is used to address more than just RAM. It
is also used to address all of the memory and some of the registers
presented by devices. Consequently, if a machine is configured with
the maximum amount of physical memory, some of that memory will be
unusable because some of the physical address space is mapped for
other uses.
</QUOTE>