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Re: fc1_x86_64 preview on tyan thunder k8w (S2885ANRF REV .03)




Alan Cox wrote:
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))

That makes sense. Thanks Alan.


So its

  0-639K		RAM
  640K-1Mb		ISA + ROM window

Is the and ISA bus on any x86-64 board? Is it possible?

I don't think you can even find a SocketA board with ISA slots.
I have a ISA card I cannot replace right now that's keept me on a SlotA board and a lowly 800MHz Thunderbird Athlon.


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.

Know which ones, if any, currently can? AMD, Nvidia, or VIA? Why would they release a chip that couldn't?

-Thomas




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