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

Warner Losh imp at bsdimp.com
Sat Sep 18 02:13:05 AEST 2021

On Fri, Sep 17, 2021 at 9:32 AM Clem Cole <clemc at ccc.com> wrote:

> 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.

V0 was for the pdp-7/pdp-9. V1 was the first port to the 11/20. V2 still
supports the 11/20, but V3 and V4 move heavily to the 11/40s and 11/45s.

We have printouts for V0. And the kernel for V1 with bits and pieces in the
V2 to V3 timeframe that folded into the Unix-Jun72 efforts.


> 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 at bsdimp.com> wrote:
>> On Fri, Sep 17, 2021 at 8:10 AM Roland via TUHS <tuhs at 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
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://minnie.tuhs.org/pipermail/tuhs/attachments/20210917/43542848/attachment.htm>

More information about the TUHS mailing list