2 Nov
2001
2 Nov
'01
10:08 a.m.
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.