Megaprocessor - built from individual transistors

Doug Ingraham dpi at
Thu Jun 25 18:10:23 CDT 2015

On Thu, Jun 25, 2015 at 10:22 AM, Vincent Slyngstad <
v.slyngstad at> wrote:

> Please correct me if I'm talking complete bulls**t. This is all
>> new to me.
> The only other concern I've had during my thought experiments
> along this line related again to the current/power involved.  The
> device is likely to become difficult to cool if you achieve a 4X
> volume reduction.
> Oh, and I guess the nightmare of soldering many thousands of
> surface mount discretes and transistors to manufacture such a
> thing.

The easy way to do this is to make one board with a small CPLD connected to
all the pins and program it to match the logic of the card you are
emulating.  That way you can have a couple of hundred boards made up for
you at a reasonable cost that are all the same but ends up with different
functionality.  Just stick a label on the handle to tell what the card was
programmed as.

I don't think you would have heat issues unless you actually tried to use
the original circuits.

The Straight 8 logic uses pulses for some things instead of levels making
it not really compatible with more modern logic.  At least not a direct
replacement.  The later models would be better targets.  An I for example
might be the best choice.

You can't shrink the size of the Front Panel because the switch spacing is
already just a little narrow for people with large fingers.  It would be
better to make it a little oversize in fact.   I don't have large hands and
it would still be better for me if the spacing was slightly wider.

Doug Ingraham
PDP-8 SN 1175

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