29 Aug
2007
29 Aug
'07
6:34 p.m.
as most of us know, the IBM PC and PC/AT (I think)
have extra rom sockets. If you want to obtain a dump
of an eprom, could you simply plug them into these
spare sockets and use Debug or whatever to capture an
image? Seems straitforward enough, but I figured it
wouldn't hurt to ask...
I should work, but there are a couple of 'gotchas'
1) The AT has a 16 bit data bus, so the 2 'spare' EPROM sockets are
mapped to the same address range, one supplies the high byte of each
word, the other the low byte (or equivanently, one contians the bytes at
even addresses, the other those at odd addresses). This is no real
problem, it's easy to take every second byte in software.
2) The EPROMs had better not be a valid PC BIOS extension, or it'll be
linked in when the PC boots. I would have thought on an AT, swapping the
2 ROMs round (or only inserting them one at a time) would fix that
3) THe EPROMs have to be the right pinout. IIRC, the PC/AT takes a
stndard 2764-27256 type of device, which is simple. The PC takes some odd
ROM type, not pin-compatible with the usual EPROMs.
-tony