Re: memory remapping, 4gb memory on 945gt

Dr. David Alan Gilbert
2008-01-04T18:19:34Z

* Andi Kleen (andi@firstfloor.org) wrote:
> felix-linuxkernel@fefe.de writes:
>
> > I recently put 4 GB of memory in my Acer Travelmate 8210 series
> > notebook. The BIOS only detects 3 GB.
>
> Actually it will detect 4GB, but put the PCI hole over the last GB.
> One way to get more usable memory is to configure the BIOS to use a smaller
> PCI hole (e.g. use smaller frame buffer/aperture etc.)

Unfortunately there are certainly some that don't make many options
for configuration and also use a vast amount; my Toshiba A100-306
uses an entire 1GB for the PCI space and has very little in the
way of configuration.

> > I googled around a little. It appears to be a chipset limitation of the
> > 945gt, which uses the fourth gig for devices.
> >
> > 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.

Dave
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