Qbus split I&D?

Johnny Billquist bqt at update.uu.se
Sun Aug 9 10:48:05 CDT 2015

On 2015-03-18 19:15, Noel Chiappa wrote:
>      > From: Johnny Billquist
>      > One more thing to check this summer...
> OK, if you can, that would really be great; if either i) it's still together,
> or ii) there are pictures, it would fill some of the key knowledge gaps.
> In particular, i) what kind of backplane is it plugged into, and ii) what is
> the UNIBUS edge connector on the card connected to...

Wow. This took me some time to get back to, and also find the mail thread.

Anyway, I can now shed some more light here.

To recap, we had multiple discussions/arguments about a memory expansion 
option for the 11/34, where lots of other people claimed that the 
Enable34 added memory, but that it was not addressable in the regular 
sense, and you mostly could use it in a bank switched way, and possibly 
DMA to it.
I, on the other hand, claimed that it worked just like normal memory, 
and essentially expanded the 11/34 to a 22-bit addressing machine. 
Making it more or less the same as an 11/24.

Turns out I understood/remembered it right, but was wrong about the 
product. The 11/34 that I played with did not have a product from 
Enable. So I really cannot comment on the Enable34, and I do not have 
any documentation on it.

The product "my" 11/34 have came from Systime, and it do expand the 
11/34 to 22 bit full addressing. The PAR registers are expanded to 16 
bits, MMR3 gets some additional bits, and you get a Unibus map.

The solution is one card in the CPU backplane. In addition, a few wires 
needs to be changed on the backplane, there is a cable from a CPU card 
to the Systime card, and a few modifications required on the 11/34 CPU 
itself. And then there is a separate box connected from the Systime 
card, which holds all the memory.
Once you have installed the Systime option, you will have an 11/34 with 
22-bit addressing. From a software point of view, the easiest is to tell 
any OS that you have an 11/24 instead, and everything just works.

We still do have the manuals, even though I'm not sure where the 
hardware is anymore. It would take some work to scan them, and I don't 
have the time for that at the moment.

I wonder, have anyone else but me ever seen/used this option?


Johnny Billquist                  || "I'm on a bus
                                   ||  on a psychedelic trip
email: bqt at softjar.se             ||  Reading murder books
pdp is alive!                     ||  tryin' to stay hip" - B. Idol

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