IBM RAM

IBM PS/2 256K 30 pin SIMM memory module

IBM RAM Back view

IBM RAM side view

I am told these RAM chips are from an IBM PS/2 computer but I have not ascertained the model yet.

The code 1497256 implies 256K but elsewhere on the web they are listed variously as 256K and 512K. I suspect there are either two IBM part codes with the same number, or the 512K part number is a dual-256K module sold as one part. They are reputed to be Parity SIMMS (single in-line memory modules), and they are 30 pin.

The modules are unusual in that the RAM chips are very thick, protruding 6-7mm off the surface of the modules. Each of the 4 chips has the codes

90X0707ESD
IBM 9314
V
18916016PA

on the top.

I would possibly dispute the parity claim on the basis they are missing one RAM chip, and they would have been used at about the time frame parity was beginning to be seen as irrelevant - RAM chips were getting more reliable and the act of detecting a RAM error wasn’t helpful - the computer stopped regardless.

We saw a lot of RAM modules that had been designed for parity, but were converted to non-parity by removing the extra RAM chip to save costs. I assume the parity pin on the module was simply ‘strapped’ in the appropriate high or low state to ensure the processor never saw a parity error.