17 Sep
2021
17 Sep
'21
10:04 p.m.
Hi Clem,
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.
There is a KT11B paging option that makes the PDP11/20 a 18 bit machine. It looks a bit
like the TC11 DECtape controller. I've got the schematics from the internet. But I
have no idea how it compares to the later MMU units from the software perspective.
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.
Yes, that is what I found too. V5 expects an 11/40 with at least 18 bits memory address
space.
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.
Too bad, but you never know what is still hidden in some attics...
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.
Yes the RK03 was the Diablo 31 with a DEC label on it. 100% compatible with RK11D and
RK05. You can swap the packs between these drives as well... So I'm hoping for a disk
image for such a drive... 😊
Regards, Roland