Re: HP82161 - really strange problem... Message #2 Posted by Tony Duell (UK) on 23 Nov 2001, 9:19 p.m., in response to message #1 by Pavel Korensky
This is a strange problem. I can think of a couple of unlikely causes and one that might be quite likely here.
The unlikely ones first : The particular part of the internal program on the 82161's micrcontroller thant handles formatting has failed, but the rest of the code is OK. Pretty unlikely. Or that the motor speed is wrong, so it can still read/write a preformatted tape, but if you try to format a tape, it manages to write a block off the end of the tape or something. Again very unlikely.
The most likely cause, I think, is that the track select circuitry has failed, and that the drive is always selecting track 0. That way it'll be able to read a tape with a few files on it (everything is on track 0 -- directory and the files), and it can write some more files to track 0
But when you try to format a tape, it writes the blocks for track 0, then overwrites them with the ones for track 1 (since the drive only ever selects track 0 due to the fault), and then can't find the track 0 blocks to write the directory to, as they've been overwritten.
Debugging that could be interesting because there are 2 custom chips (CPU and read/write chip) involved, and not a lot else.
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