Tu10 pdp11

Johnny Billquist bqt at update.uu.se
Sun Sep 6 07:14:46 CDT 2015

On 2015-09-05 20:25, Noel Chiappa wrote:
>      > From william degnan
>      > I was looking to see if references to the tm11 were "module/card" or
>      > backplane interface.
> I think pretty much all that earliest generation of UNIBUS interfaces were
> stand-alone backplanes (i.e. 19" wide things that went in an H960 in a fixed
> location, and were filled with the small Flip Chip modules); the RK11-C,
> RP11-C, RF11, and TC11 all are.

Partly correct. All early Unibus controllers which did DMA had their own 
backplanes. Which is why the NPR is obnoxious on the Unibus. Unlike the 
BR lines, the NPR is normally always just jumpered in the backplane, and 
located away from the BR lines. When DMA on single cards became more 
common, this became an obvious issue on the Unibus. You have to cut the 
wire on the backplane, and when you remove the card you either have to 
reinsert the write, or get the bug grant card that is double height, 
which also do the NPR jumper.

But non-DMA controllers were single cards even back in the early days of 
the Unibus, like the DL-11.

(Early DMA controllers were all multiple cards, so having their own 
dedicated backplanes were a pretty sane idea.)


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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