PDP-11/73 booting!

Allison ajp166 at bellatlantic.net
Wed Nov 30 18:18:05 CST 2005

>Subject: Re: PDP-11/73 booting!
>   From: David Betz <dbetz at xlisper.mv.com>
>   Date: Wed, 30 Nov 2005 18:53:32 -0500
>     To: "General Discussion: On-Topic and Off-Topic Posts" <cctalk at classiccmp.org>
>Well, I have bad news and good news. The bad news is that I was  
>unable to fix my RL01 cable. I tried a few approaches to reconnect  
>the pins I could see were disconnected and wasn't able to get it to  
>work. However, the good news is that I was able to acquire another  
>cable and that fixed the problem entirely. In fact, the PDP-11/73  
>booted off the RL01 pack the first time I powered it up. I have three  
>packs and was able to read all of them. One contains RT-11 V5.5,  
>another is a TSX-Plus system disk but appears just to boot RT-11SJ.  
>It does have lots of files on it with ".tsx" extensions but doesn't  
>seem to boot TSX. The third is a blank scratch pack.

First, Congrats!

You need TSX.SAV and TSX also is built on RT11.

>I'm now in the market for a cable and breakout panel (cab kit?) for  
>my RQDX3 controller so that I can connect an ST225 drive and an RX50  
>floppy drive to my 11/73. I know it's possible to build one of these  
>but from my experience with attempting to fix the RL01 cable, I don't  
>think I want to tackle that project. If someone has a cable and  
>breakout panel they'd like to sell please get in touch with me.

There isn't a "cab kit" for RQDXn.  The cables were all internal
and you used RQDXn in one of the BA23/123 boxen.  So you either need
a M9058 from a scrapped BA123 or a mostly torn up BA23 (micro PDP11
or microvax) you can pull the pannel from. You also need the little
switch pannel inserts from the BA123 to enable READY/OFFLINE and 

You need:

1 50 pin female to female IDC cable (max length 18") RQDXn to breakout
1 34pin female to female IDC cable (max length 30") (RX50)
1 26pin IDC to card edge (RDxx)
1 34 pin IDC to card edge (RDxx)

If your not using either of those boxes then your doing what I did 
which was to build something DEC didn't document.  The cables are
seriously are trivial and not a big a deal like those breakout boards
and the switch pannels.

Having done this I know.

>Anyway, thanks to everyone who has given me help with this machine. I  
>now have a working PDP-11/73 with 1.5mb of memory, an RX02 floppy  
>drive and an RL01 hard drive and it's all working!

Sounds like mine. ;) 


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