The only new information I can gather from those picture is it would
appear that pins 1 and 28 of the EPROMs is tied together and since 28
is Vcc, connected to +5V this would eliminate 27512 as pin 1 on a 27512
is A15, but on 2764, 27128, and 27256 it is Vpp and would normally be
tied to +5V for read. As I mentioned previously the empty position has
pin 26, 27, and 28 tied together, if the positions that are populated
with sockets are the same that would eliminate 27128 and 27256 as well,
and I would stand by my previous suggestion that it is 2764. I would
suggest that you check to see if 26 and 27 are connected to pin 28 on
those sockets to verify.
Paul.
On 2022-03-22 07:03, D. Resor via cctalk wrote:
I've taken and uploaded some larger easy to view images of the processor board
component and solder sides.
One plus is the eproms are socketed.
I've uploaded an image showing the silk screening stamp on the underside of the
eproms.
Now that I look closer at the Power Supply PWB I see it too is filled with
proprietarily marked parts (sigh).
Big Blue's curse continues.
Interestingly Xerox didn’t do this with the Star 6085 Workstation. The full
service manuals are available for download. I believe the 8010 is the same way.
I suppose I can email my contact at IBM archives and inquire about circuit
diagrams... It never hurts to ask.
I have the MiniPro TL866II Plus programmer. It does have the ability to read
the ID of ICs. Setup requires you first select IC p/n number from the list, and
then it verifies the data prior to a read or write.
It would be nice if it could ID the IC automatically. I realize there are
probably too many variables to do this safely without risk of destroying the
EPROM and/or the data written on it.
https://www.dropbox.com/s/juvn0ahnwp51k80/ProcessorPWBCompSide1.jpg?dl=0
https://www.dropbox.com/s/s4mqpxd9ksnciil/ProcessorPWBSolderSide1.jpg?dl=0
https://www.dropbox.com/s/rl26dkv3jjuip0u/PromUnderside1.jpg?dl=0
https://www.dropbox.com/s/mqok0avoqqumyuq/PowerSpplyPWB1.jpg?dl=0
Don Resor
-----Original Message-----
From: cctalk <cctalk-boun...@classiccmp.org> On Behalf Of Glen Slick via cctalk
Sent: Monday, March 21, 2022 9:17 PM
To: General Discussion: On-Topic and Off-Topic Posts <cctalk@classiccmp.org>
Subject: Re: ID UV erasable PROMS used on an IBM PC board?
On Mon, Mar 21, 2022 at 8:25 PM Chuck Guzis via cctalk <cctalk@classiccmp.org>
wrote:
The PROMs are most likely house-labeled Intel commodity parts with
JEDEC-standard pinouts, so it should be fairly easy, using an EPROM
reader, to figure out if these are 8KB, 16KB, 32KB or 64KB devices.
Some device programmers can read the manufacturer and device ID codes from a
device, if they are implemented. That would be another way to check for a Intel
standard part.
Intel 2764 - 89h / 02h
Intel 2764A - 89h / 08h
Intel 27C64 - 89h / 07h
Intel 27128 - 89h / 83h
Intel 27128A - 89h / 89h
Intel 27C128 - 89h / FCh
Intel 27256 - 89h / 04h
Intel 27C256 - 89h / 8Ch
Intel 27512 - 89h / 0Dh
Intel 27C512 - 89h / FDh
