fc1_x86_64 preview on tyan thunder k8w (S2885ANRF REV .03)
Alan Cox
alan at redhat.com
Thu Dec 11 22:42:29 UTC 2003
On Thu, Dec 11, 2003 at 04:11:26PM -0600, Thomas Dodd wrote:
> It was sort of explained before by Mark. What was ment is you _cannot_
> use the last .5G because it's mapped to PCI.
Thats the physical memory map. Because PCI is 32bit for some cards you
end up with a PCI hole (remember the ISA hole.. now we have two 8))
So its
0-639K RAM
640K-1Mb ISA + ROM window
1Mb-3.5Gb RAM
3.5Gb-4Gb PCI plus ROM plus APIC etc
4Gb->... RAM
> There may be some trick to move that though. I remember this was a
> problem for 32bit too. PCI+kernel took the last 1GB on a 4GB box, so
> processes only got 3GB. There were sopme hack to get 3.5GB on those, so
> it might be posible to get more on 64bit systems. Maybe only loose 0.25GB?
Thats different. You end up needing some mappings for kernel and user
space to be efficient when dealing with user mappings. Whether you can
get your .5Gb back depends if the chipset can remap it higher up in memory
so that the 3.5-4Gb RAM masked by PCI is remapped at the top of memory.
Alan
More information about the fedora-test-list
mailing list