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Jeff Parsons 2014-11-16 13:41:38 -08:00 • committed by jeffpar
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blog/2014/10/13/README.md
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The 8Mhz IBM PC AT 5170
---
I just added my first [IBM PC AT "Rev 3"](/devices/pc/machine/5170/ega/1152kb/rev3/) machine configuration
I just added my first [8Mhz IBM PC AT](/devices/pc/machine/5170/ega/1152kb/rev3/) machine configuration
to the list of [IBM PC Machine Configurations](/devices/pc/machine/), and not surprisingly, the new machine
fails to boot.
I call it "Rev 3" because it uses the 3rd [ROM BIOS](/devices/pc/bios/5170/) that IBM released for the PC AT,
a revision that is supposed to include support for 3.5-inch 1.44Mb diskettes -- which would be great, because I
have a number of 1.44Mb diskette images it would be nice to be able to read in a PCjs machine.
This machine uses the 3rd [ROM BIOS](/devices/pc/bios/5170/) that IBM released for the PC AT, a revision that
included support for 3.5-inch 1.44Mb diskettes -- which will be nice, because I have a number of 1.44Mb diskette
images I would like to be able to read in a PCjs machine.
Machines with this BIOS also ran at 8Mhz, so I've bumped the CPU speed up to 8,000,000 cycles/second. It'll be
interesting to see whether this BIOS also increased any of its hard-coded timing delay-loops as a result.
Since machines with this BIOS also ran at 8Mhz, I've bumped the CPU speed up to 8,000,000 cycles/second.
It'll be interesting to see whether this BIOS also increased any of its hard-coded timing delay-loops as a result.
Anyway, when I enabled ChipSet I/O port messages in the Debugger:
@ -25,4 +25,4 @@ activity:
I know what I'm going to be doing this afternoon now.
*[@jeffpar](http://twitter.com/jeffpar)*
*October 13, 2014*
*October 13, 2014*