H. Peter Anvin wrote:
Rene Herman wrote:
I do not know how universal that is, but _reading_ port 0xf0 might in
fact be sensible then? And should even work on a 386/387 pair? (I
have a 386/387 in fact, although I'd need to dig it up).
No. Someone might have used 0xf0 as a readonly port for other uses.
As support: port 80 on the reporter's (my) HP dv9000z laptop clearly
responds to reads differently than "unused" ports. In particular, an
inb takes 1/2 the elapsed time compared to a read to "known" unused port
0xed - 792 tsc ticks for port 80 compared to about 1450 tsc ticks for
port 0xed and other unused ports (tsc at 800 MHz).
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