> > All 8-bit Commodore disk drives have CPUs, period, IEEE or no. Some older
> > drives have two, one for "IP" to accept commands over the Commodore serial
> > bus and one to act as FDC. 1541s and later drives have "schizophrenic" CPUs
>
> Did any of the 'serial bus' drives have 2 CPUs? Most (all?) of the
> IEEE-488 ones do, one for the interface, the other for the disk
> controller. THey are both 6502-family devices, and are clocked on
> opposite levels of the same master clock, so that only one attempts to
> access memory at a given time. This makes it trivial for them to share
> memory, and of course that's the way the 2 CPUs in a CBM drive communicated.
>
> But every serial-bus drive I've worked on (1541, 1570, 1571) only has 1
> (6502) CPU in it.
AFAIK, this is correct. Only the IEEE drives have dual CPUs. *However* --
the IEEE 2031 is also a single CPU. The 2031 is suspiciously similar to the
1541 and analysis has shown that simply replacing the ROMs and the serial
bus connector turns a 1541 into a 2031 and vice versa. Its position on
the disk drive timeline is somewhat murky.
Still, the holdover from the original dual CPU Commodore drives persists
in all later 8-bit Commodore drives as the alternating IP/FDC modes.
--
----------------------------- personal page: http://www.armory.com/~spectre/ --
Cameron Kaiser, Point Loma Nazarene University * ckaiser_at_stockholm.ptloma.edu
-- FORTUNE: You can overcome any obstacle. Try a steeplechase. ----------------
Received on Fri Nov 02 2001 - 18:08:21 GMT