I have done some more experimenting. The strange sector counts were just caused by strange byte ordering ;-)

I have now tried reading and writing, and I have discovered a strange "problem". As I repported earlier I have to insert pauses between reads to read the "Identify Drive" data correctly. I have tried inserting a NOP instead of a 1ms pause, but that's apparently not enough.

When I write a sector (512B) it doesn't look like I have to insert pauses. The activity LED flashes briefly during the write. But when I try to read back the sector without pauses the LED stays on like the drive was expecting more reads than it detected. If I read back the sector with 1ms pauses between the reads the LED switches off as soon as the 256 reads are performed. Does this make sense? Is it likely that reads are slower than writes for some reason?

I have tried with two different drives (one old and one not so old), and they both behave the same.

If anyone wants/needs to see the schematic or some more code just ask.

Best regards,

Mikkel C. Simonsen