🚀 go-pugleaf

In article <20767@cup.portal.com> mmm@cup.portal.com (Mark Robert Thorson) writes:
>With regard to the pdp-11 and the -10, I recall a puzzling fact from the
>PDP-11 Peripherals Handbook.  Out of a large collection of peripheral products
>there was one which did not have "11" in its name.  This was the DL10
>Unibus window.  It was also unusual in that it might not return slave sync
>for a ridiculously long time, like 30 seconds.
>
>I know DEC-20's used 11/40's as front end machines.  Did they interface via
>a DL10?  Could someone briefly describe what services the 11/40 did?
>(Or it might have been labelled 11/35 -- same set of CPU cards.)

The DL10 was a DMA device that allowed a PDP-11 access to some portion of
DEC-10 memory - indeed, we still have one :-). I don't believe that it was
available on the DEC-20. It was typically used for interfacing PDP-11
comms front ends with a DEC-10. It would only handle 11/40s, but it was
possible by a little tweaking of the hardware (in the -11) to get 11/34s
to hang off it as well. In principle, it would take 4 -11s.

Generally, the 11/40s on a DEC20 were interfaced through a device called
a DTE, as (correct me if I'm wrong, someone) the DL10 needed an external
I/O bus, which was not provided on the DEC-20.

Rick Blake - University of Essex, Colchester, UK.
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