I'm looking for a specific rom for an IBM 5150 machine: rom 5700051 at
location U33.
This rom was only used on the very earliest (16-64k MB) 5150 machines.
I know Rich Cini has a disassembly of it on his site:
http://highgate.comm.sfu.ca/~rcini/classiccmp/files/PCBios.ASM
but does anyone have the original binary image?
It can easily be dumped from a working 5150 using a dos boot diskette
and the instructions at
http://mess.toseciso.org/dumping:dump_bios_using_debug/
The actual chip is an MK36xxx rom, which requires a pulse train on /CE
in order to read properly. Some eprom programmers will not read these
correctly at all, the first byte will fill the entire rom image because
the address is never re-latched. (MK36xxx roms will not read properly
without a pulse train of HIGH LOW <read data bus then set next address>
HIGH LOW <read data bus then set next address>, etc. IBM loved to use
these, for some reason, and only switched to real
2364/23256/2764/27256/etc on the ps/2 machines and the later ATs, and on
certain expansion cards such as the Xebec hdd controller on the XT,which
uses a 2764 for the z80 rom.)
The chip can be read in an incompatible eprom programmer by sticking the
chip in some solderless breadboard and wiring it to the rom socket in
the following way:
programmer A0 through an inverter(7404 will work fine) and connecting to
rom /CE
programmer A1 to rom A0
programmer A2 to rom A1
etc.
Data lines connect directly. read the rom as a 27128, then toss the
first(0x00), third(0x02), and every odd(0x0x where x is even) byte
thereafter, and keep the rest.
other than the /CE change, the mk36xxx is pinout compatible to a 2364,
which has a different pinout than a 2764 or 27128 does:
+--------------+
A7 |1 +--+ 24| Vcc
A6 |2 23| A8
A5 |3 22| A9
A4 |4 21| A12
A3 |5 20| /CE
A2 |6 2364 19| A10
A1 |7 18| A11
A0 |8 17| D7
D0 |9 16| D6
D1 |10 15| D5
D2 |11 14| D4
Vss |12 13| D3
+--------------+
P.S. does anyone have an IBM 5100 or other machine in the pre-PC 51xx
series? I'm looking for info from those, too.
Thanks!
--
Jonathan Gevaryahu
jgevaryahu(@t)hotmail(d0t)com
jzg22(@t)drexel(d0t)edu