Decisions you regret (classiccmp related)

Doug Ingraham dpi at
Fri Dec 18 10:19:21 CST 2015

On Thu, Dec 17, 2015 at 8:53 AM, Mike Boyle <tulsamike3434 at> wrote:

> --
> I did a Google search on a straight eight system and found this . .
> If this is the correct image I see a small round screen and if memory
> serves me a line
> like a heart beat monitor. Fi I am correct how in the world would you read
> this.

One option on an 8 is a scope interface.  It has a 10 bit X DAC, a 10 bit Y
DAC and a Z driver,  The 8 I have has this option but when they sold the 8
they didn't sell the storage tube scope with it.  Around 1975 or 1976 I
wrote a line printer driver for the scope for OS/8.  The dot matrix was
stored in 128 words and supported 64 character ASCII (a 4x6 dot matrix took
2 words per character).  So on that little display were 204 characters on a
line and 146 lines for the initial implementation.  Too hard to read even
for 20 year old eyes.  I think I made it do half that in each axis so
102x73.  Still small but very fast.  I used this for debugging programs.
After all the ASR 35 teletype was only10 cps.  I have not found a copy of
this driver in my stuff yet.  I am hoping it is not one of those things
that was lost forever.  And even if I had it I don't have the storage scope
so it is not usable.

I recently bought a period correct scope for the 8 and one of these days I
will get around to fixing it and hooking it up.  Not a storage tube but the
correct device for playing spacewars.

Doug Ingraham
PDP-8 SN 1175

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