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Possible Duplicate:
Windows XP and RAM 3.5GB+

I've recently installed 4GB of RAM on my server, which is running Windows XP SP2 32-bit and My Computer showed that only 3.37GB were installed. After digging Google for a bit, I couldn't find anything helpful, but I do remember reading a post in a forum regarding the motherboard using 640MB of RAM. Digging in my own BIOS, I've also found that my motherboard has also reserved that amount for its self.

Why does my motherboard reserve this memory and how can I tune it down to say 128MB?

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migrated from Jan 19 '10 at 17:42

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

marked as duplicate by Sathya, Ivo Flipse Jan 20 '10 at 8:17

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.

Sorry about that and thank you for the migration. – Tom Jan 19 '10 at 22:08

It's not your motherboard. It's the fact that you have a 32-bit OS. 32-bit addressing will only allow Windows to see ~3.3GB of memory. If you want to see beyond that, you would need a 64-bit OS.

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Then what is with the '640MB reserved' I see in the BIOS? – Tom Jan 19 '10 at 22:08
Is there an option in the BIOS for selecting architecture? Its overview page here:… shows that it supports either 32-bit or 64-bit architecture. If it's on 32-bit architecture then once again it's the 32-bit addressing limitation. Even if your mobo didn't show reserved memory, your 32-bit Windows wouldn't see more than what it is seeing right now anyway. – Glen Y. Jan 20 '10 at 13:05
no, 32-bit OS can see 4 Gb. Windows takes 1 or 2Gb for itself. What the 'hole' is, is a block of reserved space that old specifications put there ('cos 4Gb was more than anyone could imagine once upon a time) – gbjbaanb Mar 12 '10 at 20:24

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