Ok, Steve I have only happy 5.2 but I did not see any slowdown feature in it as you discribe, About: taking the lid off the 810 drive.
The happy discovery cart can and will copy just about every 16 bit 3.5 floppy drive and any format, I am now in the process of hooking up a 5.25 drive to my st. it seems the pinouts are compatable but I just realized that the drive must be double density and not high density! A searching I will go!
I still cant copy realm of impossibility even with the 5.2 software mabe the 5.3 will do it mabe not?
