Back in the day (early 90s, IIRC), there was a package called "SyDupe" from modesty-forbids. It could use up to 3 diskette controllers, each with up to 4 drives (grand total 3). Simultaneously copying three disks, sensing disk changes, so no keyboard interaction aside from startup. Stick a disk in, pull another out, sort of thing.
Ran on DOS. The three controller restriction was due to the limit of 3 8-bit DMA channels on the Peesee. All with off-the-shelf hardware. I still have a 6-floppy version in a tower case that still runs just fine. --Chuck
