KL-10B in DEC-20 [was RE: Who's rewired their house for this hobby?]

Rich Alderson RichA at LivingComputerMuseum.org
Wed Nov 26 19:27:45 CST 2014

From: Noel Chiappa
Sent: Wednesday, November 26, 2014 4:43 PM

>> From: Rich Alderson

>> We have a non-running 1090 here at the museum

> Oh, good, then you have a machine to run ITS on (along with ones for WAITS
> and Tops-10! :-)

Yes, we do, but not that one.  "It's dim, Jed."

> Just kidding (mostly); ITS did run on a KL (without hardware mods), but I'm
> not sure which model it was; it was a pretty early one.

ITS ran on exactly 1 KL, MIT-MC.  It was a "Model A" system, probably a KL10B
but I'd have to ask the owner.  It's currently in storage in Sweden.

> I know it had the external memory bus, and I _think_ it had the RH20s (I
> know it had RP's of some kind, I think MassBus, because one of them was
> dual-ported and the console 11 booted off of it, and I don't think it had
> whatever PDP-10 disk controller the KA's had). I guess it was a KL-B, then?

All KL10-based systems have RH20s.  The front end 11/40 has an RH11, and one
disk (at least) has to be dual-ported between the front end and the -10.

> Whichever one it was, anyone who wanted to run ITS on a KL would probably want
> the same model - I know ITS had custom microcode (in part to emulate the MIT
> pager, which had a different page size from the BBN/DEC one, and also because
> ITS used some custom instructions which had been added to the KA's), and
> although one could probably get that to run on a different model KL, it might
> be (an unknown amount of) work.

Yeah, I've thought about how much work it would be.  I'd prefer to start with
the MC system if I were going to run ITS on a KL.

> But, completely seriously, ITS is an amazing system, and although there are
> a few running on simulators, I'm not sure anyone has it running on real
> hardware. That would be Very Cool.

I agree.  As I noted in my response to John Wilson, I'm working on it. :-)


Rich Alderson
Vintage Computing Sr. Systems Engineer
Living Computer Museum
2245 1st Avenue S
Seattle, WA 98134

mailto:RichA at LivingComputerMuseum.org


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