Ronald G Minnich <[EMAIL PROTECTED]> writes: > I notice that the fixed MTRR for region 0xd0000 is defined as ROM. The > type is WRPROT, value 5. Does this mean cacheable? Still worse, if it is > write protected, why did DoC code even work ... After all, 0xd0000 should > not be writeable! I put a scope on the we# pin on the DoC and it is > clearly being written, once for each command to DoC. I don't think the > MTRR is disabling writes ...
value 5 write-protected is a very badly named MTRR setting. It means that reads are cached, but writes invalidate the cache line. Which sounds like it could easily explain what you are seeing. > Shouldn't all the MTRRs above 0xa0000 be UNCACHABLE up to 0xf0000, which > is ROM? The debug prints from linuxbios indicate that fixed MTRR is > enabled. It isn't clearly specified how MTRRs should be setup so the BIOS vendors are on their own. The only semi-clear spec says the BIOS should be copied into RAM, and cached that way. > This is very strange. MTRR settings are fun :) Eric
