options for replacing failed small ROMs in PDP-11

Noel Chiappa jnc at mercury.lcs.mit.edu
Sat Jun 25 09:15:32 CDT 2016

    > From: Glen Slick

    > the part is listed as DM8598-AD, where a DM8598 is a 256-bit (32x8)
    > tri-state bipolar mask ROM.
    > Some substitute T.S. PROMs include the Signetics 82S123

On my M8101, it's an 82S123, which is a tri-state programmable PROM (the
82S23 is the open-collector version of that chip). Those should be relatively
easy to obtain.

BTW, quick question: if a fusible link PROM 'fails' because one of the
fusible links regrows, is it possible to 're-program' that particular chip,
back to the 'original contents'? Some programmers might barf (because they
want the chip to be 'empty' to start with'), but maybe one of those home-brew
pgrogrammers could 'refresh' the chip (thereby avoiding using up a new chip,
when it's not really needed)?

      > From: Curtis H. Wilbar Jr.

      > Is there a file containing the image ?

I'd really like to accumulate a database of the contents of all the PROM
components for all the PDP-11 CPU's. I've got a few of them (for the -11/05),
but there are zillions more.

Anytime anyone creates one, can you please send me a copy, and I'll try and
get them organized and uploaded (and if I _really_ get ambitious, I might try
and start filling in the gaps).


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