PDP-8/I Negative-bus termination

jim stephens jwsmail at jwsss.com
Wed May 5 03:23:19 CDT 2021

On 5/5/2021 12:03 AM, Josh Dersch via cctalk wrote:
> Can anyone with negibus experience point me in the right direction?
As you and Ethan helped me with on FB about my 8/I, I don't know which 
bus I had.  And worse it
went to a second rack with about 10 of the expansion racks built out 
with decoders (W103s IIRC)
and the like.  I couldn't afford or justify the custom stuff in that 
rack because other than the manuals
for the 8/I it was all undocumented.  I bought a bunch of what I recall 
were 1949 racks and some
cards from the broken up system and the 8/I. I didn't think to ask for 
termination, but it had to be
at the end of a bunch of cables that they pulled apart.

I think there were 5 or 6 sets of 6 (?) or so cables daisychaining the 
peripherals all together.

Obviously you have checked whether the cards Vince mentioned (or the 
termination) in your
rack.  If it was the main external peripheral one would hope they were 

Otherwise a scamble to find some or make some.  If you do the latter, 
let me know as I'm sure I'll be
interested and would be glad to buy some PCBs to make it cheaper to get 
a run made.


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