S-100 Bus

From: Allison J Parent <allisonp_at_world.std.com>
Date: Wed Oct 6 22:14:24 1999

<If you're an S-100 user, particularly if you have experience in bringing =
<up a system from totally dead to totally alive, I'd certainly like to =
<see what your impression of your needs from such a device might be.

I've brought up several IMSAIs, Altairs, NS*, Netronics explorer 8085,
several mongruls and my multi-CPU s100 crate.

Front pannel systems were rich enough to accomplish the task one the FP
was known working or nearly so. Often the problems were dirty switches,
broken wires, failed oneshots or maybe a bad LED. Other problems were the
older boards that didn't like Bus pins 20 and 70 (protect/unprotect).

Must haves:
        
        ability to display memory
        ability to write to memory
        Start, stop and single step the CPU

Most front pannel systems (alatir, Imsai, Ithica intersystems, PDA-80 have
the basic resources. A scope may be needed if there are timing issues
or one shots that are drifted off.

The non front pannel systems required a FP that could be plugged in. the
easiest way was a a minimal CPU (Computime SBC880) that can drive the bus
but is otherwise self contained. That and a terminal is as good as a front
pannel (better).

The multi-cpu system needed more as the CPUs were not commercial units
IE: they never worked before so they had to be debugged first and that
required a bus logic analyser (capture bus state 1024 cycles deep) that
could trigger on specified conditions. This was needed to look at the
interaction of the many cpus and DMA devices. Once the system could run
code predictably (could still crash but reset to rom monitor was reliable)
The bus analyser was almost by un-needed.

A simple logic proble was the single common tool besides a frontpannel or
its analogue. A multi trace scope was handy for altairs (too dam many
oneshots!) and other system where the problem was logic that was damaged
from lightining (my old NS* system).

Allison
Received on Wed Oct 06 1999 - 22:14:24 BST

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