Nicolas, could you maybe have a look? The logic in FDC_SetIRQ() seems
quite new to me - something goes wrong there so that GPIP does not get
set to low... Do we maybe have to call FDC_ClearIRQ() somewhere else
in the HDC code?
After doing some reading, I think the IRQ line of the HDC should be
disabled right at the start when a new command byte is sent (and of
course it has to be enabled again once the byte has been accepted).
I've committed a fix, EmuTOS now seems to recognize the ACSI disks
again.