Re: [uCsimm] Why was the 68000 bus not exposed

From: Carl M Holmberg (
Date: Thu Sep 14 2000 - 04:07:26 EDT

Welcome to the world of the electrical engineer. Imagine yourself
between classes over at Ryerson, sketching out an embedded controller
design for which you harbor some whacked out fantasy of selling to the
general public. Primary considerations: 1) Useful, 2) Produceable, 3)
CHEAP. If RT-Control hadn't managed to keep the price point down at the
~US$200 level, there would have been little interest.There are already
plenty of $1K devices.

I suspect that even now a built in IDE controller would be an unwanted
cost for most customers, and at the time the design was frozen, 72 and
168 pin hardware wasn't rock bottom cheap enough for a device that
wasn't intended as a completely opened up prototyping system such as
Motorola sells.

There are h/w designs and software available that can be molded to
provide IDE for the uCSIMM, and Tom Walsh has a working 72-pin design on However, if my reading of past email and his EZ328SIMM
page is correct, Tom's intent is only to provide the design, not to
contract with someone to crank it out. The cost analysis of making do
buying off the shelf vs. building the expanded design is left as an


Richard Laxton wrote:

> I have two fairly fundamental questions:
> 1. Why was no IDE interface designed into the uCSIMM?
> 2. Why was the M68K bus not exposed for use by the
> experimenter. When you look at it the IO is pretty pitiful considering
> the plethora of IO available at the CPU. This makes retrofitting for
> Q1. a lot more difficult.
> [snip]

> The new device could have the following integrated peripherals:
> - IDE interface prehaps with DMA support
> - Colour LCD support (built in to the MC68VZ323)
> - Ethernet
> - Full MC68K bus exposed for additional peripherals. This
> would make it easy to develop new powerful peripherals such as high
> speed mutichannel A/D samplers or whatever.

Carl M. Holmberg   Maui High Performance Computing Center
808.879.5077x279   550 Lipoa Parkway, Kihei, HI 96753   email   spam

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