21MX proms (per request

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. Best, J