Virtual/physical/bus accesses (was pre 2.1, AHA1542 fixes)

Keith Owens (
Thu, 26 Sep 1996 23:16:38 +1000 (EST)

On Thu, 26 Sep 1996, Linus Torvalds wrote:
> [snip]
> So when the CPU wants any bus master to write to physical memory 0, it
> has to give the master address 0x80000000 as the memory address.
> [snip]

Interesting (as in "May you live in interesting times" :). I can see
one problem here, the need to distinguish between address 0 meaning
"byte 0" and address 0 meaning "no data present". Does not affect x86
because both map to bus 0, but might be a problem for other systems.
Could result in a situation where 0 != NULL.