ID UV erasable PROMS used on an IBM PC board?

Paul Berger phb.hfx at
Mon Mar 21 19:19:05 CDT 2022

They won't be 2732 as the EPROM in the picture has 28 pins, but 2732 is 
a 24 pin package 2764, 27128, 27256 and 27512 are all in 28 pin packages.

The 8519602 does look like an IBM house number but unfortunately it is 
not listed in the cross reference I have .

I would agree it should be fairly easy to figure out what they are by 
looking at the circuitry surrounding them.  The unpopulated U3 position 
beside the EPROM looks like it might be for another EPROM and it looks 
to have pins 26,27,and 28 all tied together on everything larger than a 
2764, pin 26 is A13 so my guess would be 2764.  If you read a 2764 as a 
27128 the upper and lower halves of the image will be identical because 
the A13 pin is not connected on a 2764 so you would effectively read the 
EPROM twice.  Pin 26 tied high would eliminate anything larger than a 2764.


On 2022-03-21 20:49, dwight via cctalk wrote:
> The dies look to have consistent wire bonding. That would mean they are one of the standard EPROMs made by Intel, just preprogrammed by Intel before shipping. The numbers wouldn't be intel numbers they would be IBMs inventory numbers. My guess is that they are 2732s. You might use a microscope and look at the edges of the dies. They often have the die type in the metal layers around the edge some place. Avoid using florescent ring lights as a large amount of UVC leaks from these. White LED are or incandescent lights.
> Also power it up and note which pins look to have signals. if any of the lines have what looks like a constant voltage measure it to the nearest .01 volts if you can. That will help determine if it is driven by a signal or a hard tied wire. Lower left and upper right should be ground and power pins.
> Dwight
> ________________________________
> From: cctalk <cctalk-bounces at> on behalf of D. Resor via cctalk <cctalk at>
> Sent: Sunday, March 20, 2022 6:53 PM
> To: 'General Discussion: On-Topic and Off-Topic Posts' <cctalk at>
> Subject: ID UV erasable PROMS used on an IBM PC board?
> I cannot find a datasheet by any of the numbers silkscreened on these ICs.
> Could these be proprietary IBM P/N numbers?
> No need for a Dropbox account, close the login pop up and you can view the
> image.
> Thanks
> Don Resor

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