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)? 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). Noel