IBM 5150 rom: 5700051 at U33 - anyone have this?

[Mark L. Weindling]

Any luck on this yet? If you're still stuck, let me know and I'll see  
what I can do.

-Mark


On Aug 30, 2008, at 9:07 PM, Jonathan Gevaryahu wrote:

>
> 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
>