At 2004-06-09 13:20:31 +0530, [EMAIL PROTECTED] wrote:
>
> A 32 bit processor system can address upto 4GB of memory.

Depending on the processor, it may be able to access more memory. Many
32-bit systems now support hacks like PAE (Physical Address Extension)
to support more than 4GB of physical memory. The linear address space
is still 4GB, so the kernel has to map highmem pages into the normal
zone before they can be used.

For an explanation of PAE, look at the "More Information" section of:
<http://support.microsoft.com/default.aspx?scid=kb;en-us;268363&sd=tech>

You may also want to read:
<http://www.skynet.ie/~mel/projects/vm/guide/html/understand/>

> (1) If a system has 4GB of physical RAM for a single 32 bit processor,
> will the OS be able to use virtual memory, considering all of the
> addressable virtual space is physically available. ?

Sure. Each process has its own page tables that can address the entire
4GB memory space, and the kernel can swap pages out from one process's
address space and make those pages available to another process under
memory pressure.

Of course, no single process can allocate more than 4GB (in fact, with
a 1:3 kernel:user split, the limit is 3GB).

> (2) What is the maximum amount of virtual memory which Linux (2.4 or
> 2.6) use / provide ?

I'm not sure, but it depends on the architecture.

-- ams

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