17 Jul
2015
17 Jul
'15
9:21 a.m.
On 07/16/2015 11:45 AM, Mike Stein wrote:
Not the same thing of course but remotely on-topic,
and I never miss an
opportunity to put in a plug for Cromemco:
By comparison, Cromemco used semi-autonomous 4MHz Z80A SBCs for their
I/O processors, with 16KB of local RAM and up to 32KB of ROM;
communication with peripheral cards is via a separate 50-pin 'C-Bus'.
That wasn't all that uncommon in the microprocessor world--once the
price dropped sufficiently, doing multiuser applications by giving each
user their own CPU was practical. Molecular was another outfit that did
practically the same thing.
Dual-CPU setups, where the "weaker" of the two CPUs was in control of
the "stronger" one were even more numerous--just consider the number of
"add in" processor cards for the PC archicture. 68K, NS32xxx...you name
a CPU, it's probably been on an ISA card.
And there's the veneered and generated Radio Shack 68K series (16, 16B,
6000) where it's the Z80 that starts things and controls the show
initially, even if you're running Xenix.
In pretty much all cases, the system is capable of running without the
"stronger" CPU.
--Chuck