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4GB memory seen as 3GB in BIOS

4GB memory seen as 3GB in BIOS

I have a 945GCM S2L Motherboard which has 4GB memory (2x2GB) running windows vista x64.

Asked by: Guest | Views: 42
Total answers/comments: 4
Guest [Entry]

"Maybe there is a shared memory used by graphics card? Some cards use main memory from computer in order to display contents of the screen.

Look for shared memory (or video memory) and make the value lower."
Guest [Entry]

"GigaByte GA-945GCM-S2L

2 x 1.8V DDR2 DIMM sockets supporting up to 4 GB of system memory

Try update BIOS"
Guest [Entry]

"Some bioses seem to default to have memory mapping (or re-mapping) disabled which means you can't see the full 4Gb. (Some don't even give you an option to enable it). So that would be the first thing to look for. (Of course, every BIOS will probably describe it slightly differently)

Is there any way of updating BIOS from
a x64 Vista installation,

If the update utility won't run, you need to find boot into a operating system that will run it. Some manufacturers give a dos or linux install that can run when you boot from a floppy (if you have one) or a cd.

(I keep having to remind myself that not everyone has a Rescue Disk like Bart CD , but that's what I would use)."
Guest [Entry]

"On a 32 bit XP computer you just cannot use the whole 4GB of physical RAM. It'll always be capped at 3GB.

What happens is that the 32bit processor's use 32 pointers to address the bytes in the RAM. So there are 2 raised to the power 32 (2^32) possible addresses. But, in addition to RAM a good number of these addresses are also used to address other memories like the BIOS, the video memory etc. This uses up one fourth of the 2^32 addresses previously mentioned. So you're left with only 2^30 addresses for the RAM.

These many addresses can address no more than 3GB of RAM (2^30 = 3GB).

This is the reason you're only seeing 3GB of installed physical memory. It has got nothing to do with whether you've a shared video memory or not. This limit will exist in ALL 32bit computers.

In windows XP there is a way to go around this limit. It's called Physical Address Extension (PAE). This can take you up to 4GB (but not beyond). I'm not sure how to enable it. Try googling for it."