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SubjectRe: [PATCH] Cleanup port 0x80 use (was: Re: IO delay ...)
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> > documentation on the ISA bus which covers the timeout for acknowledging an
> > address cycle. Otherwise for tsc capable boxes I agree entirely.
> >
> The ISA bus doesn't time out; a cycle on the ISA bus just happens, and
> the fact that noone is there to listen doesn't seem to matter.

Not so simple. I found my IEEE draft 8)

The address out comes from the chipset (southbridge now days). The
sequence is

BALE high
Output address
BALE low
Set IORC/IOWC etc

Wait for NOWS while watching IOCHRDY

NOWS low says - card now ready
IOCHRDY high suppresses the wait state timer count

The default timeout is 4 wait states, which is 6 bus clocks for a failure
Maybe 7 - Im not clear if the final cycle to recover and start again is
always there.

> The delay is something like 8 cycles @ 8.3 MHz or around 1 ms.

1uS ?

Alan
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