I certainly used a CoCo floppy drive unit (the FD501 one I think) on my Model 3 for a time, so it should work on the Model 4 too (same disk controller). And I see no good reason why it wouldn't work on a model 1. I even used one of those cheap mechanical printer swtichboxes (with 36 pin Blue Ribbon connectors) to switch the drives between the CoCo and the Model 3. Made up a couple of cables with edge connectors on one end, Blue Ribbon on the other, and crimped a Blue Ribbon plug onto the cable coming out of the drive box. Looking at the mess of wiring inside the switchbox told me it shouldn't work (noise everywhere!), but amazingly I had no problems... -tony