[reaperducer]

Can you upload code to be executed on a stock 1541/1571?

Yes. There were disk duplicators that ran entirely on the drives.

You'd upload the program to a pair of daisy-chained drives, put the source disk in one, and the destination disk in the other and they'd go about their business.

You could then disconnect the computer and do other things with it while making all the disk copies you wanted.

I've always wanted a modern equivalent. I thought FireWire might make it happen, but it didn't. And it's my understanding is that USB doesn't allow this kind of independent device linking.

The closest thing I've seen in modern times was a small box I got from B&H that would burn the contents of a CF card onto a DVD-RW.