Hi. I recently acquired from local aftermarket a Quadlink board. It uses unusual DISK II drive controller, which is very picky in relation to diferent 360K PC drives. Roughly 40% of my otherwise perfectly working PC drives are reading well diskettes writteln by standard Apple2 computers. The rest fail when used to read Apple2 diskettes. The problem occurs with decent error rate on external tracks usually from 0 to 9. The more the head moves to inner tracks the more the "non working with qudlink" PC drives read flawlessly inner tracks. If these less compatible drives write an A2 diskette on quadlink then that diskette is readable on a standard Apple ][. Now I think quadlink's specific implementation without the Wozniak PROM state machine is quite picky to some timing signal parmeter but I am wondering which is that. The schematics of the clone is here:
https://github.com/schlae/quapple/blob/main/Quapple.pdf
What puzzles me more is I found by chance a couple of diskettes written on Apple2 DISK II drives over 10 years ago by me that can be read by all 360K PC drives I connect to quadlink, incl. those "uncompatible". If I make a copy of these diskettes on a real Apple2 the copy works nicely on Apple2, but no longer is read by Quadlink. If I make copy on the quadlink witha second (drive 2) writing "less comptible" 360K drive then the written diskette is read by all 360K and Apple2 drives I tried.
I am able to run copy plus sector editor, or any other software on quadlink, or apple2 and provide what is read for your considertion with a "non comptible PC drive", and by your instruction. I am inclined to think it is a design flaw due to the fact Quadram had to void the original Apple's disk controller design...Any ideas are welcome...
For testing purpose I programmed and installed a new set of PALs from Quapple, no changes in disk drive opertion with them was noticed from this situation.