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Old April 18th 10, 02:39 AM posted to alt.comp.periphs.mainboard.gigabyte
Paul
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Posts: 13,364
Default gigabyte p55-usb3 and bios

Barry Watzman wrote:


Your original premise was wrong. It is perfectly correct for a
*Microsoft* 32 bit OS, when confronted with 4GB of physical memory,
to report only 3.4GB is free. This is an address space problem, and


Although the conclusion is correct, the explanation is wrong, and what
is going on is not "Microsoft specific".

A 32-bit OS (or CPU) can only address 4GB of memory. But the HARDWARE
(in particular, the motherboard, the BIOS and the video card .... also,
often the network card and even the sound card) will use a significant
chunk of that SPACE. For example, for the BIOS, for Network DMA
buffers, for the video memory (or the window into it) and, in the case
of soundcards, for things like "wavetable storage". Note that it is
memory addressing space that is being used, and not actual memory
itself. However, this makes that memory unavailable to the Operating
System (ANY operating system, including Mac and Linux if they are
32-bit) for program storage. So the OS reports something like "3.4GB"
of memory available, even though the system may have more (indeed, may
have a LOT more).

The only way to circumvent that is to use a 64-bit CPU with a 64-bit OS.
That {approximately} 0.6 GB will STILL be used, but there is no chance
that, with a 64 bit address space, it will reduce the amount of physical
memory available to the operating system.


It is the mapping from virtual address space, to physical address space,
that makes it possible for a 32 bit program, to access a chunk of
a much larger physical address space. As described here.

http://en.wikipedia.org/wiki/Physical_Address_Extension

Paul