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Slower with 2 CPU? 4 Gig Total RAM but 3 Gig only Registered?

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Last response: in Systems
May 27, 2010 3:18:12 AM


I have a home-built high end workstation

2 x 3.0 Ghz Intel Xeon Dual Core 5160 (Both Identical)
2 x 2 Gig 667 FBDimm RAM (4 Gig Total)
PCI-E Nvidia Geforce GTS 250
700 watts PSU
500 GB SATA Hard Drive
Intel S5000Xvn Workstation Motherboard

ISSUE 1: By looking at the FPS while benchmarking with 3DMark, it seems that I get more FPS using 1 CPU than 2. Why is that? Is that normal? Usually I get 700 fps with 1 core then I went to bios and enable multi core processing so that 2 CPU is running and then I get only 400 fps.

ISSUE 2: I installed 4 Gig identical FBDimm RAM. It registered 4 gig at BIOS and when I go to My Computer General property tab, it only says there 2.99 total RAM

More about : slower cpu gig total ram gig registered

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May 27, 2010 3:46:18 AM

On Issue 2, I bet you are running a 32-bit OS. A 32-bit OS can only generate addresses up to 4 GB. So as it deals with ANY form of RAM, whether your mainboard RAM or that extra on your video card, it can only handle that much.

Now, in order to use the RAM built into your video card, it has to reserve a certain address range for that, and thus the portion of mainboard RAM in that same address space is NOT available to use. Then if we look at the OS itself, it will load into a chunk of mainboard RAM at the bottom end of the address range, then reserve a bit more of that RAM space to use itself exclusively. In total, it it typical for the OS to consume 0.3 to 0.5 GB of RAM.

My guess is that you have a 512 MB video card. Reserving 512 MB of address space for that video card RAM, plus about 0.5 GB for the real mainboard RAM actually occupied by the OS, you find that the RAM address range that is available for use as "Free Space" comes to about 3.0 GB. This is normal in 32-bit OS's.

This is why people are moving to 64-bit OS's. Their address generation ability is HUGE! If you did that on your machine, it would reserve an address range for the video card RAM that does NOT overlap some of the mainboard RAM, and you would be able to use that extra 512 MB of RAM. But you still would have about 0.5 GB occupied by the OS. Of course, in that situation IF your mobo could handle it, you might be able to add more RAM and expand beyond 3.5 GB of Free Space.