Serial UNIBUS Repeater?

tony duell ard at
Mon Jun 15 12:11:03 CDT 2015

> I'm not specifically familiar with the 11/730, but what's wrong with just cabling up an expansion box "the old 
> fashioned way" using BC11A cable?

Nothing electtically... 

The problem is that the 11/730 mouting box (BA11-Z??) is a bit odd. The boards go in from the left. Cables end up
going downwards (either straight down or over the top of the card cage, then down between the backplane and
PSU). Then into a removeable tray on the bottom of the mouting box, round a flexible plastic sheet and to another tray fixed in the rack. The idea is to make the cables route nicely when yout slide the box in and out (something
you have to do on the 11/730 to change the microcode tape or get to the main circuit breaker).

I am not sure how a BC11A cable would like being folded back and forth like that. The official way was, I think
a board in the Unibus out slot of the 11/730 that had 3 40 pin Berg headers on it. This took 3 normal 
40 way ribbon cables which went round the cable routing thing and to a similar board in the Unibus in slot of the
expansion box. I think there were even bulkhead panels to route the cables to another rack cabinet.

I have the boards and cabling somewhere...

My 11/730, which is a 'to be started soon' project has 4M of RAM and thus 2 spare hex height
slots. One contains a DMF32, the other a TSU05 tape controller. I have a half-rack to put it all in.
Obviously I am putting the CPU and R80 drive in that rack, the question is what else. I think an RL02
is pointless (the Integrated disk controller in the CPU of an 11/730 will talk to up to 4 drives. One can
be a R80, the others are RL02s). The obvious thing is a TS05 (Cipher F880) tape drive, I have one but with
a wrecked door so it needs repairs. I wonder if a Unibus expansion box would be more use though.

Incidentally : 

It appears the DECSA (ethernet comms server) PSU is the same PSU as that in the 11/730 with the memory
PSU board left out. The schematics are in the 11/730 printset, they are not in the DECSA printset. Similarly
the LA100 printset doesn't include the PSU schematic, the LA210 one does, and it's the same unit again.

Totally useless coincidence that I noticed while doing a cryptic crossword : 

'ethernet' is an anagram of 'three ten', and the original ethernet speeds were three and then
ten megabits/second.


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