Hi..
 > OUT 4Fh,AL
 > Makes a dandy pause. Apparently the ports below FFh all operate
 > at 8-10 MHz, and the CPU will sit quietly waiting for the OUT
 > to finish (unlike IN). The trick is to find an unused port to
 > write to, and 4Fh seems to be the one.
I tried a number of modern and old M/B's to see if port 4fh is accessed by 
the BIOS (Using a POST card setup for port 4fh instead of the usual 80h. This 
post card also indicates the presence of a READ from a port, as well as 
writes).
I found port 4fh to be completely unused in any board tried. You seem to have 
found a good port to use! I wold sugest that port 80h is a good second 
substitute as almost every modern BIOS writes POST codes to this port, which 
suggests that writes here are quite harmless.
As for creating a fixed delay; this "trick" has been used both in the crynwr 
packet drivers and in Linux... therefore I'd say it's probably pretty 
reliable. The source code (linux?) I've studied also suggests that this works 
on a MCA computer, however, the MCA machine delays approximately half the 
time of an ISA bus machine (IE the out is twice as fast).
    Craig
--- FMail/386 1.0g
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