[Leaplist] Only seeing 3G memory

[Bryan J. Smith]

From: Bryan J Smith <b.j.smith at ieee.org>
> Again, the system is "seeing" all 4GiB, but _no_
> PC can _ever_ access all 4GiB under 4GiB, hence why it is less.
> It's why Windows Home/Pro can only support 3GiB (no
> PAE support), and why you have to load a x86-64 or i686 PAE
> kernel to access al 4GiB.

Just to clarify, this is only partially accurate.

Most 32-bit, non-PAE kernels (Windows, Linux, etc...) use
a 3/1G user/kernel memory model.  In the kernel space, memory
mapped I/O and other reservations are accounted for as well.

That's why 1G is typically a "safe" kernel address space/size,
although it can be larger if there is a lot of memory mapped
I/O going on.



-- 
Bryan J Smith        Professional, Technical Annoyance
b.j.smith at ieee.org  http://www.linkedin.com/in/bjsmith
------------------------------------------------------
I'm a PC, but Linux -- Windows: Life Without Firewalls



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