26 Oct
1999
26 Oct
'99
1:28 p.m.
Allison wrote:
I think you got that backwards. VME and 68k were
synchronous. The PC
bus is async (as is s100, Multibus, U and Q busses)!
No, it was right.
The 68K internally sychronizes the DTACK/ signal to a clock, but as far
as the bus goes, the clock is not needed. It's fully asynchronous. This
is explained very clearly in the 68000 data sheet.
On the other hand, the PC bus requires cards to either (1) operate at
the exact speed the computer wants, or (2) provide handshaking synchronously
to the bus clock.