Ok never mind.. managed to solve it by putting the new tape drive in the old server, had to change a few jumpers and switches but it worked. :) Thanks very much for all your help!
The SCO box has no network cards, basically everything runs over serial connection (I tried transferring the data with Kermit, Zmodem etc.) but I kept getting some sort of data transfer error.
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I'm trying to create a tape backup of a list of files on a 10 year old server, running SCO Openserver 5.0.5 (the tape drive is a Seagate STD224000N,...