bouyer@antioche.lip6.fr asked:
> Does someone know if the ST506 specs are available on-line somewhere
> (I doubt - altavista didn't find anything).
>
> If someone knows how it works - I suppose the alternate register status
> doesn't exist on ST506 drives/controller (it has the property
> to not ack the interrupt on IDE systems, where the status register does) ?

If you need to know about alternate status registers, what you need is
the programming spec for the IBM PC/AT hard disk controller card, not
the ST506 spec.  ST506 is the electrical interface between the hard
disk controller card and the disk drive, not the programming interface
of the controller.
-- 
Andreas Gustafsson, gson@araneus.fi