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From: Roland via TUHS <>
To: "" <>
Subject: Re: [TUHS] Unix for PDP11/20 w/o mmu or paging option
Date: Fri, 17 Sep 2021 16:04:12 +0000 (UTC)	[thread overview]
Message-ID: <> (raw)
In-Reply-To: <>

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 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

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  reply	other threads:[~2021-09-17 16:04 UTC|newest]

Thread overview: 17+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <>
2021-09-17 14:09 ` Roland via TUHS
2021-09-17 14:33   ` Warner Losh
2021-09-17 15:32     ` Clem Cole
2021-09-17 16:04       ` Roland via TUHS [this message]
2021-09-17 16:14         ` Clem Cole
2021-09-17 16:44           ` Roland via TUHS
2021-09-17 16:13       ` Warner Losh
2021-09-17 16:17         ` Clem Cole
2021-09-17 16:05     ` Roland via TUHS
2021-09-17 15:35 Noel Chiappa
2021-09-17 18:28 ` Phil Budne
2021-09-17 19:43   ` Clem Cole
2021-09-17 19:51     ` Brantley Coile
2021-09-17 20:07       ` Clem Cole
2021-09-17 21:21       ` Phil Budne
2021-09-17 20:18 Noel Chiappa
2021-09-17 20:47 ` Clem Cole

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