homebrew 'puter project (was: 8008?

Chuck Guzis cclist at sydex.com
Wed Nov 16 12:14:12 CST 2005


On 11/16/2005 at 12:56 PM Roger Merchberger wrote:

>
>>Why have a backplane at all?  That much RAM is what, one or maybe two
>>chips?
>
>How else could you pull a 6809 card, stick in a 68K card, and still use
>the 
>same RAM / keyboard / etc.? Or pull out one ROM card (say, running OS-9) 
>and put in another, running something else. ;-)

I know I'm probably suffering from something akin to USB-itis, but even
"slow" serial busses are pretty darned fast now and I really like not
having to lots of traces for bus transceivers, etc.  I'd be sore tempted to
just hang on a USB controller to whatever CPU card I was building and
forget about a backplane.

I know--it wouldn't be suitable for display in a nice lucite case with
plenty of blinking lights!

Which reminds me of something that happened within a couple of months of
getting my Altair 8800 going.  I'd very carefully toggled in someone's 12K
BASIC interpreter and gotten it to run and actually execute some small
programs.  Way cool, I thought.  So I invited a co-worker over during the
lunch hour to see what I'd accomplished.

His reaction was one of unabashed scorn.  "THAT'S A COMPUTER?"  said he.
"I THOUGHT YOU WERE WORKING ON SOMETHING MORE THAN A TOY."  The words still
sting today.  I imagine that if I'd had a 40hp MG set in my living room, or
a few CDC 607 tape drives he might have been more open-minded.

I suppose he had a point.  What I'd spent on getting that Altair and SWTP
TV Typewriter going would have bought a big hunk of a Porsche 914 back
then.

If I were to build a system from chips today, I'd probably relegate all of
my I/O devices to some commodity interface, using single-chip
microcontrollers where some particular intelligence was required.  Leave
the CPU free for the heavy computational lifting.

Cheers,
Chuck





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