Replying to a message of James Vahn to Darryl Gregorash:
 JV>>> page of ports are always on the 8MHz bus, and port 4Fh is
 JV>>> always unused, so a stable form of jmp $+2.
 >>  
 >> I think it would be highly unwise to rely on this being true
 >> forever.
 JV> I seem to recall that 4F was mirrored on the motherboard in
 JV> some way and impossible to use in any real fashion..? I
I don't know; if it is, it isn't part of any standard that I know of. The 
only port use list I have is about 5 years old. 
Unless something is stated as reserved for future use, eg. in the ISA 
specifications, or is otherwise in use, anything that is not used should be 
free for grabs.. 
  JV> Here's a clip from the Linux kernel. He uses port 80h, which
 JV> shows in a port list as being used for DMA.. Any comments?
 Yeah.. the list I have shows 80h as free, but again, that list is 5 years 
old. Even if it is free, since 81h is already in use by a DMA controller, 80h 
is one I would be absolutely sure to stay away from :)
--- FleetStreet 1.20 NR
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