Introduction and need help bringing some pdp11's back

Pete Turnbull pete at
Tue Oct 29 13:13:57 CDT 2019

On 29/10/2019 16:28, Chris Zach via cctalk wrote:
> The real problem is I'm trying to put an RQDX3 in there instead of the 
> ESDI controller so I can boot off RX50's. And I have no idea which way 
> all the various ribbon cables are supposed to go. Will any 50 pin cable 
> work between the RQDX3 and the BA23 distribution bulkhead? Anything 
> special about the 34ish pin cable that goes between the bulkhead and the 
> RX50? So far when I try to boot all devices DU0-3 give me not yet ready.

Welcome back!

No, there's nothing special about either the 50-way ribbon cable or the 
34-way ribbon cable.  Just don't use a PC-style floppy cable with a 
twist in it.  DEC did it the way God (and Alan Shugart) intended.  But 
which distribution bulkhead have you got?  I assume not an M9058, 
because that's a card with lots of options that goes in a Q-bus 
backplane and wants jumpers setting.

Either way, you might find this file helpful if you want to work out 
what's going where:
and maybe even a glance at this one:
because it shows the relationship between the connectors and the signals 
a bit better.

Pete Turnbull

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