21MX proms (per request

[Jay West]

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

Who had been through this problem and does it "really" worth to have some
blanks "just in case" ??
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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.

Best,

J