DEC 11/45 build - advice sought, parts requested possibly.

Tony Duell ard at
Fri Jul 8 18:11:17 CDT 2005

> Ok, so I have a working processor, and a basement full of peripherals. I'm 
> not sure which way to go with the rest of the build. I'm not really up on 
> DEC stuff I admit, so maybe others here can offer me some advice as to what 
> is the best way to proceed.
> Background:
> My 11/45 (11/45-CA actually) has the KB11-A processor, no FP. It's the older 
> style with the power distribution board on the back wall of the cpu cabinet 

OK, mine is like that. I rebuilt the power harness to give me an extra 5V 
feed from another regulator block to the expansion backplanes. The stock 
system is a bit current-limited there.

> rather than on top. However, it's also got the newer 861A power control in 
> the bottom rather than the dual 860's in the top. There is the two H742A's 
> as well. I have one system unit installed - MF-11L in which is installed 8K 
> of core. In the cpu backplane there are three unibus slots which I believe 
> will take three quad? (C-F) boards. A&B in two of those slots are used for 

Yes, they are standard SPC slots. Don't forget you'll have to play around 
with the NPG jumper on the wire-side of the backplane if you put a DMA 
device -- like an RX211 -- in one of those slots.

> the unibus A to unibus B jumper, and A&B of the last slot is the connector 
> to A&B of the MF-11L. The MF-11L has a 9312 in the last A&B slot. The SPC? 
> boards currently installed are two DL11's and a M7228. The ONLY board in 
> slot one is a 930C terminator in A&B. I have no MMU, so slot 13 is empty and 
> slot 14 has the M8116.

Pity. You really need that MMU. You are limited to 28kW of memory without 

> Separately, I have a lot of peripherals to choose from. Scads of RL02's, 
> DSD440, LincTape II, RX01's, RX02's, RA81's, etc. I also have a BA11-KU with 
> a DD11-DK backplane in it.
> Problem:
> The unibus space on the cpu backplane is quite limited. At the VERY least I 
> have to keep one of the DL11's there, so that leaves me with two more unibus 
> slots for peripherals. I *THINK* that that standard controller for an RX02 
> or RL02 takes all 6 rows (Hex cards?). However, the DSD440 controller only 

The RX02 controller (RX211) is a quad card and can go in the CPU 
backplane. The RL11 is a hex card though.

> takes slots C-F (quad?). The linctape II controller also only takes C-F. So, 
> I think I could have a reasonable system by putting the DSD440 controller, 
> LincTape controller, and a DL11 and be done with it. However, I then am 
> limited to using core memory in the MF11. At the very best, I can get... 

YOu have space for 3 'system units' behind the CPU backplane. The MF11, 
IIRC, takes up 2 of them. You can fit a 4-slot backplane in as well. If 
you are mildly eccentric, you can wire-wrap said backplane to be 2 quad 
SPC slots, 2 hex SPC slots with MUD wiring on the top 2 connectors. That 
might be enough for you.

> what... 32K in a MF11? I think I can get the additional core boards. But 
> correct me if I'm wrong but isn't sticking with core (max 32K) going to make 
> my operating system choices extremely limited? I'm guessing I can't run RSTS 
> or Unix on it with that kinda memory. vtserver I think requires a full load 
> of 128KW. On top of it all, the DSD440 takes most of the rack depth, as does 
> an RL02, so I've been advised against mounting anything above the /45 except 
> maybe the linctape.

I would only put a 'short' unit immediately above the 11/45 CPU, but 
above that you can put an RL or something. 

> Possible solutions:
> 1) I just got a M7891 (64KW) off Ebay. I could yank out the MF-11L system 
> unit, yank out the DD11-DK from the spare BA11, and install the DD11 in the 
> cpu cabinet. I'd use the unibus memory M7891, ditch the core, and have a 
> fair number of slots left over in the DD11. However, there's problems with 
> this approach. I'd still be mounting stuff above the /45 (DSD440 & Linctape 
> at the least), and maybe an RL02. In other words, this would fix the memory 
> and unibus slot availability, but I believe I'd still be restricting the 
> airflow/cooling too much :\ Plus I'd need to find some of those rare Mate & 
> Lock connectors to get the DD11 into the /45 cabinet and do some power 

The easiest place to find those connectors is to raid current-loop serial 

> harness building. I guess I might need one or more regulators for this 
> approach as well. Then I'd have to find/buy a KT11-C to USE the M7891 I 
> think.... I'm probably talking about unobtanium stuff aren't I :|


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