26 Apr
2018
26 Apr
'18
5:30 p.m.
On Thu, Apr 26, 2018, 15:59 Bill Gunshannon via cctalk <
cctalk at classiccmp.org> wrote:
I believe the Z-80 was subordinate to the M68K.
In high-level conceptual term, maybe, depending on the software.
In term of the actual capabilities of the hardware, the Z80 was firmly in
control of _everything_ in the machine, including control over the MC68000,
while the MC68000 had no direct control over anything but its MMU (built
from TTL) and memory. If code running on the MC68000
wants to talk to
anything at all, disk, tape, console, printer, serial ports, etc.,
all it
can do is politely request that of the Z80. In that sense it's like the CPU
of a CDC 6600, which can't do anything without the PPUs
The Model 16 was developed
independently of the Model II.
The Model 16 was developed as an expansion of the already-existing Model
II, with a few other changes like half-height floppy drives that were later
implemented on the Model 12 also.