Memory problems - Server 2003 64 addresses 3.2gb only. Intel 945G

We've got a development/test server running Windows server 2003 64bit, standard edition with SP2. (it also has dual boot to the 32bit edition)

How can I diagnose problems with memory? I'm worried we've got a faulty stick of RAM, but I want to check I haven't just missed a config setting somewhere before I get on the phone to Crucial.

The RAM's been upgraded to 4gb but windows (64bit) doesn't seem to be recognising the full 4gb. Task manager reports "3406152 kb" and system properties "3.25 gb".

Even more confusingly the BIOS reports only 2gb.

Extra Info: The hardware is basically a cheap desktop. It's got a Pentium 4 ("ACPI\GENUINEINTEL_-_EM64T_FAMILY_15_MODEL_4_0") in a Foxconn 945G7MA-8EKRS2 (intel 945G).

It's been years since I tinkered with hardware, and never in a 64bit or server OS, so I'm out of my depth.

From serverfault Andrew M

• Have you tried MemTest86? It's an ISO that you can download and it will punish your system for a while with all kinds of tests for your memory.

  Suggestion: if you suspect one memory module over the other, put it in the closest DIMM slot to your CPU. A potential problem with this approach may be that a memory module isn't bad, but rather a DIMM slot is bad.

  From pcampbell

• The 945G chipset has a 32-bit memory controller. Typically it reserves 256MB for video memory, and the other 512MB will be used for other resources that use direct memory access (DMA) or memory-mapped I/O. On a 32-bit system you would only be able to access all 4GB (and probably be able to install more than 4GB) of memory if the chipset supported physical address extensions (PAE).

  Your memory is fine. This is the limitation of your chipset. In fact, I'm running on a 945G-equipped system right now with 4GB of memory installed, 3.25GB usable.

  gbn : Spot on. Chipsets need to be 965 or above to support > 4GB RAM properly http://en.wikipedia.org/wiki/List_of_Intel_chipsets

  Andrew M : Thanks - that explains it. :)
  From The Lazy DBA

• Isn't PAE disabled in 64-bit Windows? From MSDN:

  "PAE is supported only on 32-bit versions of the Windows operating system; 64-bit versions of Windows do not support PAE. For information about device driver and system requirements for 64-bit versions of Windows, see 64-bit System Design. The Address Windowing Extension (AWE) API is supported on 32-bit systems. It is also supported on x64 systems for both native and Wow64 applications."

  http://www.microsoft.com/whdc/system/platform/server/PAE/pae_os.mspx

  I don't know about the 945G-Equipped System but I would yield to Lazy DBA that the problem lies there. I just don't think that PAE will solve it with a 64-bit OS. I am interested to hear other suggestions, though.

  From Shane Corellian