On Thu, Feb 25, 2021 at 1:43 PM Chris Zach via cctalk <cctalk@classiccmp.org> wrote:
> Oh this is fun stuff. Is there a specification write-up anywhere on the > MASSBUS overall? > > For example I wonder if the RH70 could do a transfer >128kb at a time. > Another is around the RH11: There were two models, the traditional RH11 > (which could only do so many words on a DMA transfer) and the RH11-C > which could do more words per transaction by basically running the > Unibus in "Hog mode". That allowed the 2020 to run RM03's at a full 3600 > RPM (and I assume can allow the 2020 to run things like RM80's). > > Another item I always wondered about was the RH11's support of two > unibuses. I think the idea was to do the data transfers on the second > bus right to an 11/45's FASTBUS memory without worrying about DMA > timeouts while running the control and status registers on the normal > UNIBUS (which wouldn't block other devices). I wonder, does the MBA on > an 11/70 use similar cards to an RH11? > > C > > > I have a UNIBUS array of backplanes from an Industrial 11/40 that has a lot of MASBUS controllers in it. Or, I think that's what these are. I removed the backplane chassis from the rack and replaced it with two RL02 drives. https://www.vintagecomputer.net/digital/PDP11-40_industrial11/DEC_industrial11_exp_chassis.jpg