Re: [TUHS] Unix for PDP11/20 w/o mmu or paging option

FYI: The KS11 MMU for the 11/20 was built by CSS and was not on the product list as it were. To my knowledge, no hardware or prints of it survive. I've been told it was much more similar to the MMU in the KA10 than the scheme eventually done for the 11/45/55/70 and the 11/40 class systems - but I think Noel has done more investigation than I have. So if others have more info, please chime in. As Warner points out the oldest code base we have is Fifth Edition. I'm not sure if the KS11 code is still there. I did not think so. I thought it ran on 11/40 and 11/45. The V1 work was for a PDP-7 and is before the first 11/20 was secured. The point is that I think there is a hole in the the SW we have.

As for RK03 vs. RK05 -- *I think I can help a little*. RK02/RK03 used an RK-11C. I'm fairly sure that the RK05, used the RK11-D controller. The '72 peripherals' handbook describes the former and the '76 the later. But if you believe the handbook, both supported 203 cylinders and 2.45M bytes/disk with 512 byte sectors. The difference seems to have been in drive performance. On Fri, Sep 17, 2021 at 10:34 AM Warner Losh <imp(a)bsdimp.com> wrote: > > > On Fri, Sep 17, 2021 at 8:10 AM Roland via TUHS <tuhs(a)minnie.tuhs.org> > wrote: > >> Hello Unix fanatics, >> >> I have a PDP11/20 and I would love to run an early Unix version on it. >> I've been working on the hardware for a while and I'm getting more and more >> of the pieces back online again. The configuration will be two RK05 hard >> disks, TU56H tape, PC11 paper tape reader/puncher and a RX01 floppy drive. >> Unfortunately I don't have a MMU or paging option. But it seems that the >> earliest versions of Unix do not need the extra memory. >> >> Does anyone have RK05 disk images for these early Unix versions? That >> would be a great help. Otherwise it would be great to have some input about >> how to create a bootable Unix pack for this machine. >> > > V5 is the earliest Unix we have contemporary images from. We have > fragments from everything else earlier, including files scavenged/recovered > from early DECtapes and some code recovered from kernel listings from a > Unix course that was put together by Bell Labs... > > The Unix 1972 project that some TUHS members did. I think it's in the > TUHS distribution archive, but also on github. I think Warren Toomey's repo > is the canonical one https://github.com/DoctorWkt/unix-jun72 but > https://github.com/c3x04/Unix-1st-Edition-jun72 has a couple of newer > fixes for a docker file to contain the simh simulator. I'm unsure what > hardware that's supported, though. The machine file suggests: > > rk03/rk11 177400 disk RK > dc11 174000 tty? (not supp?) > tc11/tu56 177340 dec tape DTn (not showing up in simh?) > rf11/rs11 177460 fixed head disk RF > kw11-l 177546 clock CLK > pc11 177550 paper tape PTR/PTP > asr-33 177560 tty? TTI, TTO > > which has an RK03, not sure how close that is to an RK05, so some tweaks > may be needed. > > Warner > > >> A bit about the hardware restoring is on the vcfed forum: >> >> https://www.vcfed.org/forum/forum/genres/dec/78961-rk05-disk-drive-versions >> https://www.vcfed.org/forum/forum/genres/dec/80723-pdp11-20-restoring >> >> Booting RT11 from RK05 >> https://youtu.be/k0tiUcRBPQA >> TU56H tape drive back online >> https://youtu.be/_ZJK3QP9gRA >> >> Thanks in advance! >> Roland Huisman >> >> >> >