[Simh] Potentially stupid questions: PDP-11/RSTS and PDP-10/TOPS-20

[Rich Alderson]

> Date: Wed, 28 Apr 2010 18:59:33 +0800
> From: Michael Richter <ttmrichter at gmail.com>

> Question #1: I'm trying to find some programs to put into my RSTS system and
> stumbled over some files on BitSaver that I can't figure out.
> (http://bitsavers.org/bits/DEC/pdp11/dectape/ would be an example.)  They end
> in .dta and seem to be viable tape images of some kind when I inspect the
> contents.  For example
> http://bitsavers.org/bits/DEC/pdp11/dectape/rsts/SeattlePacificCollege/158_ahl_basic_games.dta.gzhas
> a whole bunch of BASIC source files which appear to be in perfect order.

>  Yet I cannot find any combination of SIMH attach and RSTS mount commands
> that will allow me to actually access the contents of these.  What, if
> anything, is the trick to accessing these mysterious "DTA" formatted images?
>  Is there any kind of tool to convert to a format that SIMH supports?

Michael, SimH supports these perfectly well on its own.  These are images of
DECtapes, not the sort of tapes you have in mind.  DECtape controller may not
exist for later PDP-11 models, but were generic on 12-, 18-, 36- and 16-bit
computers from DEC for decades.  Look at the documentation for the PDP-11
simulator for more information on DECtape handling.

> Question #2: I want to start tinkering with TOPS-20 under SIMH, but I can't
> find a sysgen tape image that boots.  Every one I've tried so far after
> attaching and using SIMH's boot command has just led to SIMH sucking up all
> my CPU and doing nothing else, even if left alone for hours.  Does anybody
> know of a known-good tape image to sysgen a TOPS-20 installation from that
> works under SIMH?

Other people have answered this, mostly discouraging you from using TOPS-20 on
SimH.  Version 4.1 works perfectly well, and will teach you some things about
old systems.

If you insist on having the very latest OS release, then yes, you will have to
use KLH10.  SimH only provides a KS-10 processor, on which TOPS-20 development
ceased at 4.1--although Mark Crispin *did* port 5.4 while at Stanford, he lost
that stuff a long long long time ago.  KLH10 provides both KL-10 and KS-10
processors (the latter mostly for ITS support).

Or you can just get an account on the Living Computer Museum's XKL Toad-1
running TOPS-20 v7.1, to see whether you like it or not before diving into the
guts of KLH10.


Rich Alderson
Vintage Computing Sr. Server Engineer
Vulcan, Inc.
505 5th Avenue S, Suite 900
Seattle, WA 98104

mailto:RichA at livingcomputermuseum.org