24 Feb
2013
24 Feb
'13
1:58 a.m.
On 24/02/2013 08:59, Nigel Williams wrote:
We've had some success decoding the various LSI
chips found within the
IBM Displaywriter System, in this case the external 8-inch floppy
drive subsystem (IBM 6360), but one last chip has stumped us, or more
accurately stumped our Estonian colleague who was familiar with the
IBM to Intel part number mapping, see here:
http://www.cpu-world.com/forum/viewtopic.php?p=164045#164045
Anyone with knowledge of how to implement the NEC D765D floppy disk
controller in a detached setup might be able to make a good guess as
to the function of the remaining 40-pin DIP IC (labelled 4430030) in
the picture?
http://i.imgur.com/VtMxSqj.jpg
is it another peripheral chip or perhaps a CPU? I'm guessing the
former since I don't see anything that might hold ROM code for a CPU.
Most of the date codes are towards the end of 1981 so 8144 is the latest
I can see. Thats around the time of the IBM PC announcement and I know
that used an Intel 8048 as a keyboard controller.
So an 8048 or similar, but if so why the 8225A as the 8048 would have
enough I/O lines for a floppy controller.
The Intel 4178628 to the right is an Intel 8255A-5
(Programmable
Peripheral Interface (PPI)).