On Fri, 28 May 2010, Zane H. Healy wrote:
  Can a C1541 or C1571 attached to a C64 read
floppies from other Commodore
 computers such as the VIC-20 or C16?  Since the floppy drive is basically
 a computer attached to the C64 by a serial cable, I tend to think it can,
 but I don't believe I've ever seen anything on this, and I know I've never
 tried. I've never had a floppy drive attached to any of my VIC-20's, back
 when it was my only computer, I only had a cassette drive.
  
 Zane, the short answer is yes.  The long answer is yes, because the brains
 of the drive and the DOS are IN the drive itself, not the computer. :)
 The only difficulty you might run into is trying to read a double sided
 1571 disk in a single sided 1541. 
 I thought this was the case, but just couldn't believe Commodore could have
 done anything so logical. :-)