Re: large memory support for x86

From: Brian Gerst (
Date: Fri Oct 13 2000 - 14:07:42 EST

Timur Tabi wrote:
> ** Reply to message from Ingo Molnar <> on Fri, 13 Oct 2000
> 20:44:19 +0200 (CEST)
> > processes are not limited to a single segment, eg. Wine uses nonstandard
> > segments. But as i said, using multiple segments does not let you out of
> > 32 bits of virtual memory.
> Sure it does, just like segments let 16-bit apps access more than 64KB of
> memory. If you have two selectors, each one can point to a different physical
> base address, and IIRC, the size of the physical address base can be 36 bits.
> That gives you 16 physically contiguous 4GB memory blocks.

You missed the point. The layering on the X86 memory managment is such:

Virtual Address <- limited to 32 bits
Physical Address

Segmentation never directly gives you a physical address, even in real
mode. Although in real mode virtual address is hardwired to physical
address. Virtual addresses are always 32 bits on the x86. In real
mode, in protected mode, and with PAE enabled.


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