21MX proms (per request

Jay West jwest at classiccmp.org
Fri Sep 11 15:35:40 CDT 2015

Gerard wrote....
HOW OFTEN theses old PROM fail  ?? 

Who had been through this problem and does it "really" worth to have some
blanks "just in case" ??
1) Once is enough, if it is the only known copy of that particular rom. But
in general they are very reliable. More often than not - when they fail -
something else took them out in the process of it's failure. I have had a
prom failure all by itself though.

2) It's extremely worth it. For one.... many of the machines run by people
on this list immediately become boatanchors if a prom fails, especially if
it's a microcode rom. Second... you're missing the more general case - say I
have a HP21MX that was running 2000/Access and I now want to run RTE-6/VM.
Guess what - I need the microcode roms that are required for RTE-6/VM.
Fortunately, other collectors have taken the time to copy their proms and
upload them online (bitsavers is a great example). So I can download their
rom images and burn a new set for running new software I had not been able
to run before. Another example - say my machine came with only paper tape.
Two years later I happen to acquire a disc drive. Sure would be nice if I
could just download the loader rom image and burn it so that I can boot from
that device. With a burner and blanks, all that is possible.



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