I haven't been following this thread too closely so I may have missed
something, but it seems to me that the proposed solutions are overly
complex. One simple solution that comes to mind is to define a set of
vendor unique SCSI commands, one for each of the registers in the IDE
command stack and then do all the emulation in the device driver on the host
side. The interface card is just then a simple state machine; really simple
if u make it a non arbitrating protocol implementation and use PIO for data
transfers (SCSI-1 lives :-).
Tom