Vista 32bit not recognizing 4GB RAM - The Final Word

[Guest]

I have created this post before, but I will give one more try. None of the
discussions I have seen to date answer the question.

I have 4x1Gb RAM installed. Vista recognizes 2.93Gb and BIOS recognises
3008MB. I changed the Memory Remapping option in BIOS to Enabled. BIOS
recognises 4GB (4096MB) and Vista now recognizes 2GB. I installed
VistaBootPro and Enabled PAE (Physical Address Extension) mode. There was no
difference in the RAM recognized by Vista.

Some postings on these forums claim that certain devices (such as video
cards) are reserving part of the physical address space for their device
drivers. That successfully accounts for the difference between 3GB and
2.93GB. It does not account for the difference between installed RAM (4GB)
and the available RAM (2.93GB). Installed hardware devices cannot possibly
reserve more than 1GB of physical RAM.

In order to test my hypothesis, I removed 1GB RAM, giving me 3GB installed.
Vista shows 2.93GB of available RAM, precisely the same as was available with
4GB installed.

I can only conclude that unless there is a switch in the BCD file that
Microsoft has not told us about, Vista 32bit can only use 3GB RAM. Microsoft
should make clear the maximum amount of RAM that can be used by Vista 32bit,
under what circumstances it can be used, and how to use it.

 

[Tom Lake]

I have 4x1Gb RAM installed. Vista recognizes 2.93Gb and BIOS recognises

3008MB. I changed the Memory Remapping option in BIOS to Enabled. BIOS
recognises 4GB (4096MB) and Vista now recognizes 2GB. I installed
VistaBootPro and Enabled PAE (Physical Address Extension) mode. There was
no
difference in the RAM recognized by Vista.

Your motherboard can't handle the PAE switch. Some can and some can't.

Some postings on these forums claim that certain devices (such as video
cards) are reserving part of the physical address space for their device
drivers. That successfully accounts for the difference between 3GB and
2.93GB. It does not account for the difference between installed RAM (4GB)
and the available RAM (2.93GB). Installed hardware devices cannot possibly
reserve more than 1GB of physical RAM.

Sure they can! Each PCI slot takes RAM addresses, The VGA Aperture takes
RAM
addresses, The BIOS takes RAM addresses, the Video BIOS takes RAM addresses,
All sorts of devices take up RAM addresses. Not all of these are fully
decoded so that
even if a peripheral only needs 100K of address space, it might be seen in
the actual 4GB
address space as taking 512 MB.

Some motherboards won't allow the PAE switch to work. The RAM area use by
the peripherals is moved above the 4 GB mark but there's no way to get at
it.

Tom Lake

 

[Guest]

Although this link address WinXP, it clearly states the problems with the 3GB
limits imposed on 32-bit machines. Typically, the graphics card is hard coded
where it will reside in memory as handled by the OS resulting in memory above
that address not being available.

http://h20331.www2.hp.com/Hpsub/downloads/RAM Allocation w-WinXP_HP MWP x64 03Nov05.doc

To see if this is the case, pull your graphics card and allow the on-board
video to take over. Depending on it's addressing, you may see as much as 3.5
GB available.

While your hardware may not be using all that memory, it may be hardcoded to
addresses which prevents the OS from using the gaps.

 

[JW]

Here is the link to the MD KB article on the subject.

http://support.microsoft.com:80/kb/929605/en-us

 

[Joe Guidera]

Bear in mind, we're talking RAM "Addresses" and not necessarily actual RAM.

J

 

[Richard Urban]

Please. The final word has been posted numerous times. Or do you want the
final - final word, in hopes that it will change?

--


Regards,

Richard Urban MVP
Microsoft Windows Shell/User

 

[Zim Babwe]

I think he wants the final word for today.

Please. The final word has been posted numerous times. Or do you want the
final - final word, in hopes that it will change?

--


Regards,

Richard Urban MVP
Microsoft Windows Shell/User