Re: memory remapping, 4gb memory on 945gt

[H. Peter Anvin]

Dr. David Alan Gilbert wrote:
> > > Now I can understand this explanation for 32-bit mode, but I'm running
> > > in 64-bit mode.  There should be a way to use the fourth gig under
> > > Linux.  Is there?
> > The chipset limitation applies to 64bit mode as well as to 32bit mode
> > (which actually does not have a 4GB limitation with PAE)
>
> Note that some system and memory vendors have incorrect statements
> stating that the 3.xGB limit is a 32bit OS issue on these machines
> and it'll all just work fine on 64bit OSs.

Supposedly WinXP-32 doesn't use memory over 4 GB even if it is available 
(a market-segmentation decision of the part of Microsoft, to force 
people to buy WinServer 2003; WinXP SP2 does PAE so there is no 
technical reason.)  This probably has disincentivized hardware vendors 
from providing support for remapping the memory from the aperture above 
the 4 GB mark.  The logic isn't all that trivial, especially if the 
aperture size is configurable, so I can understand why they would punt.

	-hpa
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