11/45 hack?

[John Wilson]

On Thu, Feb 12, 2015 at 05:11:07PM -0500, Noel Chiappa wrote:
>I seem to recall reading (don't remember where, it was a long time ago) of
>some place that actually made use of the dual UNIBUS thing; they hung some
>other PDP-11 (don't recall what kind) off UNIBUS B, and ran a primitive
>multi-processor. It was some sort of high-speed data acquisition, or perhaps
>a real-time simulator - something like that.
>
>Anyone else know of any place that used the dual UNIBUS capability?

The ones I've run into were flight simulators (I think one was a 727?)
that used two PDP-11/45s, running DOS/BATCH I think, with the memory
shared via the split Unibi on the memory controller.  There was also
an IPL (I forget -- DR11Bs or DR11Cs?) connecting the two.

Ersatz-11 emulates this config, in an unsupported way of course.
Ironically, the FASTBUS: pseudo-device is actually slower than regular
memory (since every access has to be mP-safe), but still way faster
than real 11/45s.  But that's what IPL: is for (as a pseudo digital
I/O device).

John Wilson
D Bit