I have the following machine configuration:

  • Intel Core 2 Duo E6300
  • 1 x 2048 MBytes memory chip
  • 2 x 1024 MBytes memory chip
  • 1 x Radeon HD 4870
  • Motherboard : Gigabyte 945P-S3
  • Windows 7 RTM 64-bit

In both Windows and the BIOS I have 3.25GB memory available. How can I enable it to support 4GB?

EDIT: I've sort of upgraded the CMOS version, and Windows acknowledges I have 4GB but is only using 3.25GB.

alt text

I guess it is hardware after all?

migrated from serverfault.com Sep 4 '09 at 13:24

This question came from our site for system and network administrators.

  • I'm fighting the same battle right now. Pretty sure we're hosed with the i945 chipset. Granted, I'd love to be proven wrong! – Chris_K Sep 4 '09 at 13:18

Your BIOS needs to support memory hole remapping.

Memory hole is there since all devices must fit in 32-bit address space during boot (since BIOS is not aware whether you will use 32-bit or 64-bit OS later). Remapping takes care to move affected memory to memory area after 32-bit boundary.

I would check whether new BIOS firmware is available if that setting is not in your current BIOS firmware.

  • Yes, there is a newer firmware version. Right now I've F2 installed. I will try to update, right? bit.ly/M0Fgv – ArielBH Sep 4 '09 at 9:25
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    @ArielBH: yes, update is almost always a good thing. – Josip Medved Sep 4 '09 at 10:11
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    Strangest thing. I tried to update the CMOS. I did every step by the book. The cmos failed to load. I had to clear the CMOS. CMOS is up again, and now when I check the version, it indicate the new version, how can it be? – ArielBH Sep 4 '09 at 13:34
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    @ArielBH: It is definitely strange. I would try to update it once more just to check whether it updated everything. Most BIOS update routines check whether old BIOS fits ok. – Josip Medved Sep 4 '09 at 15:54
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    @josip frankly I feel lucky that I've managed to get the cmos to work again. I think I will not touch it anymore :) – ArielBH Sep 4 '09 at 21:33

Josip is correct that the BIOS with memory hole remapping is necessary. As Chris_K tries to say your hardware must also to be able to physically address more than 4GB see KB929605. I believe that the Intel 945 chipset family cannot do this. So, sorry to say you are out of luck.


Windows 7 x64 should recognize that RAM with no fiddling required.

If the BIOS doesn't recognize all 4 GB, there's no chance Windows will see it. It's possible that the reason they provide a memory support list is because the board is very choosy.

I would each of your ram sticks individually, to make sure the BIOS sees them correctly.

Now that I'm thinking about it, the SU guys are going to have a lot more experience with this.

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    Josip is probably right - did you find any options related to memory hole remapping in the bios? – Kara Marfia Sep 4 '09 at 12:54

It looks like the 945 chip set doesn't support more than 4 GB of address space (and some versions only 2GB). So you end up with the same limitation as Vista 32 bit - you won't be able to use all of 4 GB of your RAM since address space is used for more than just RAM.

From the Intel 945 chip set datasheet page 24:

The (G)MCH supports 32-bit host addressing, decoding up to 4 GB (2 GB for the 82945PL/82945GC/82945GZ) of the processor’s usable memory address space

And of page 205:

Addressing of memory ranges larger than 4 GB (2 GB for 82945GC/82945GZ/82945PL) is not supported


The manual for your motherboard doesn't say it is a requirement, but it does advise using the same size memory modules. It's possible that having 1gb modules being scanned first is preventing it from detecting the larger 2gb module.

I would try swapping which bank the modules are in ( 1x2gb <-> 2x1gb ) and see if that helps, failing that I think you just need to get two 1gb modules to replace your existing 2gb module.

Of course, the up-side of the latter would be that you'd re-enable dual-channel and get faster memory use of the system.

  • Yes, I had those 2*1GB chips. My last visit to Redmond, USA i've bought 2 chips of 2GB. As it happens one of them was faulty, so I got stuck with only one (and I live abroad USA). – ArielBH Sep 4 '09 at 13:43
  • Yeah--I would never mix memory chips like that. It's not the culprit but it's just asking for trouble. – Loren Pechtel Sep 4 '09 at 15:48

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