Reproducing old machines with newer technology
mhs.stein at gmail.com
Thu Jul 16 13:45:58 CDT 2015
----- Original Message -----
From: "Chuck Guzis" <cclist at sydex.com>
To: <General at classiccmp.org>;
"Discussion at classiccmp.org:On-Topic and Off-Topic
Posts" <cctalk at classiccmp.org>
Sent: Tuesday, July 14, 2015 5:47 PM
Subject: Re: Reproducing old machines with newer
> On 07/14/2015 02:05 PM, Jay Jaeger wrote:
>> Going all the way back to at least the IBM
>> 7090, and presumably the 709,
>> though I have not actually checked. The B5000
>> had IO processors as well.
> Again, you're missing the point. The system
> *starts* with a PPU and loads the CPU up to run.
> OS was pretty much entirely within the PPUs.
> PPUs have autonomous access to the entire memory
> space of the CPU and use the "exchange jump" to
> switch it to a task.
----- Reply -----
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
What's interesting and sort-of-relevant is that
later versions of Cromix (their UNIX work-alike)
could use the IOP to run Z80 programs, especially
useful in a system having only a 680x0 main CPU.
FWIW, their hard disk controller also used a 4MHz
Z80A with 8KB ROM and 64KB RAM that could cache 4
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