CoCo Xpndr1 (was: RE: Keep or assemble???

From: Roger Merchberger <>
Date: Tue Sep 4 16:46:48 2001

Rumor has it that David Woyciesjes may have mentioned these words:

> It sounds like you would get more enjoyment out of building & using
>it, rather that letting it sit and collect dust. If you're toying with
>building it, I would say go for it, but keep all the packing and paperwork,
>too. That helps increase the 'value'.
>I think it all depends on whether you plan on selling it, or keeping it. I
>would definitely build & use it.

[snippage, fore and aft...]

I don't necessarily disagree with you, but the "reproducability" would be
decreased once the kit is built... i.e. you can't [easily] scan the boards,
or re-design them in AutoCad, etc...

With this in mind, I was digging thru an old box of CoCo stuff I have and I
came across (2) Xpndr1 expansion cards, 1 of which is virgin. A quick
search of Google shows nothing about them...

I've started re-designing the card in AutoCad (as if I didn't have *enough*
projects ;-) with improvements. Some are minor, like putting the signal
names on the top of the card instead of the bottom (so it's easier to see
the signal names when I attach a small breadboard to the top of the
card...) some are major (or going to be) like the extra room for standoffs
so it'll be self-supporting, and also connector ports for both a "PC hard
drive power port" and a "PC floppy drive power port" so you can power the
thing from any PC power supply *or* an FD-50x power supply. I also plan on
having one that buffers all of the data, address & major signal lines on
the board, so that experimenting might be easier without blowing the entire
CoCo bus.

Which leads to my questions:

A) Anybody know anything about the company that marketed these, as I don't
want to intentionally break any copyright laws; but with no info on the
internet & the extreme possibility of the company no longer existing, does
anyone think I'll be in trouble with the law WRT copyright laws? I'm mainly
just using the original as a pattern for (1) the signal names & pinouts,
and (2) the dimensions of the connectors & pins (I didn't have anything
else that had the ground pegs on either side of the connector).

B) I can prolly find this out for myself, but there are many others here
better than me on the hardware side of things: What would be some of the
better [a.k.a more useful] buffer chips I could use to buffer the address &
data busses?

C) Are there any *real* problems with powering the card from a separate
power supply? I'm assuming I need to tie the grounds together, but I
wouldn't want the +5 / +12 / -12 volt rails tied at all -- they should be
separate, right? [[no, I really don't feel like dissecting my MPI just
yet... altho I think it's the *only* piece of computer equipment I've never
taken apart! ]]

        Should I check the voltage levels of the power supply & the CoCo to see
how close they are, or as long as they're both within TTL levels is it OK?
I'm mainly worried about the PC supply being of a higher voltage than the
CoCo, if that'll cause problems.


The designs (when they get closer to completion) I will have on my website
for free, but if I make several cards and someone else is dumb^H^H^H^H bold
enough to purchase one I would sell them for a small profit...

Anywho, thanks for listening, and double-thanks for any advice that others
might be willing to offer... ;-)

Roger "Merch" Merchberger
Roger "Merch" Merchberger   ---   sysadmin, Iceberg Computers
Recycling is good, right???  Ok, so I'll recycle an old .sig.
If at first you don't succeed, nuclear warhead
disarmament should *not* be your first career choice.
Received on Tue Sep 04 2001 - 16:46:48 BST

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