Ok folks, I have found the issue with the format track function. I was writing a preamble of one 0xff followed by all zeros, due to a programming error. With that error, it’s surprising that I could find any sectors at all. Fixed that and the first track is written cleanly and I can read it back reliably. However I must have a bug in the verify track portion of the format function, as the format disk routine quits after writing one track. As RosanaRosana Danna would say – “it’s always something”

I’m moving my Disk II to PC interface blog from my Disk II page to this page, in order to give visitors a chance to add in their comments. Visit the disk II interface page if you want an overview of what this project is about.
http://www.willegal.net/appleii/appleii-disk-int.htm
The initial blog entries about this project are on that page.