Talk:Incompatible Timesharing System

From Computer History Wiki
Revision as of 13:39, 13 April 2021 by Jnc (talk | contribs) (Move MC config thread here)
Jump to: navigation, search


I'm pretty sure that by the time I got to Tech Sq (in 1977), the PDP-6 was no longer in use. It wasn't physically removed until some years later, though. Jnc (talk) 15:43, 14 December 2017 (CET)

Right. I have collected all information I have found on each of the classical ITS machines here: [1], but I figured it was too much for this page. User:Larsbrinkhoff 18:14, 14 December 2017 (CET)


Comment on "after Multics was done". I believe both Multics and ITS were developed around the same time. User:Larsbrinkhoff 11:11, 15 December 2017 (CET)

Well, the planning for Multics I believe started first; 1964 or so (the timeline on the Multicians site doesn't give the exact date, but they selected GE in 1964, so it was certainly underway then). The first boot of a Multics came in December '67. As for ITS, the AI Lab history, "A Marriage of Convenience: The Founding of the MIT Artificial Intelligence Laboratory" implies that it was started, and finished, sometime in '67, on a PDP-6 already owned by the Lab, but no specific date is given. Jnc (talk) 14:49, 15 December 2017 (CET)
It seems right that Multics implementation started well before that of ITS. But they become operational at about the same time; actually ITS was first. Project MAC Progress Report IV has this to say: "A time-sharing system for the PDP-6 went into operation in July 1967." User:Larsbrinkhoff 15:31, 15 December 2017 (CET)
Good find! I'll add that to the article. Jnc (talk) 15:43, 15 December 2017 (CET)


I found this posted to alt.sys.pdp10: "The [TENEX] exception model for system calls was as ugly as their hardware, instead of adopting an ITS-like PCLSR approach - another step backwards from the 940 system, which in essence had simplified PCLSR." Larsbrinkhoff (talk)

MC configuration

So I'm trying to work out MC's configuration. (I know, I know, I could look in CONFIG >, but I'm lazy.) Here's what I remember/can work out:

  • 8 MF10's
  • (later) An Ampex? 'external' memory box was added
  • 3 RP04's
  • So, therefore, some sort of MASSBUS controller, but since it was a KL10 Model A, not an RH20; probably an RH10
  • That would have needed a DF10
  • A TM10 of some sort; dunno if that had a separate DF10, or shared the one the RH10 used
  • Some sort of high-end DEC magtape drive
  • A DL10
  • Later, first one, and then a second Trident drive, attached to the DL10 PDP-11
  • The front-end -11 had a bunch of serial lines, probably a DH11
  • CHAOSNET eventually on the DL10 PDP-11
  • I'm not sure why they initially acquired the DL10+PDP-11 (i.e. what it did to begin with); probably more serial lines

Well, that's a start. Jnc (talk) 17:09, 12 April 2021 (CEST)

I have tried to summarize changes to CONFIG > for all machines over the years:
Most of what you wrote seems spot on. I can see there was a third T-300. Yes, initially the DL10 front end was just a normal DC76 handling terminals. Larsbrinkhoff (talk) 17:29, 12 April 2021 (CEST)
Where is CONFIG > now? I looked here: here but it doesn't seem to be there. Jnc (talk) 17:47, 12 April 2021 (CEST)
Many (all maybe?) versions are here: Larsbrinkhoff (talk) 17:51, 12 April 2021 (CEST)
Ah, thanks.
It looks like it doesn't say what kind of tape drive it was; it was a TU77, or something. If we ever get good photos of the machine, we should be able to tell (also, if there was a second DF10).
I wonder why they did the whole DL10 thing just to get a few more serial lines. Maybe the DTE20 one was maxed out?
I see from the IOELEV/KLDCP source that the DTE20 -11 had a TU56; I vaguely remember that. Jnc (talk) 18:53, 12 April 2021 (CEST)
I only know of one photo of MC when at MIT, the one on the ITS page, but there's no tape drive. I saw MC in LCM storage, but I don't remember any peripherals. Larsbrinkhoff (talk) 18:59, 12 April 2021 (CEST)
Here is the layout of the machine, as best as I can remember it. The tape drive would not have been in the field of that image.
A couple of notes. I'm sure of the CPU, MF10's, Fabridrek Ampex, RP04's, Tape, Trident and DL10 locations. The RH10/DF10 were I think in that corner, but I'm not positive, and I don't remember which order. Ditto for the order of the DL10 and its PDP-11 (which I think was an 11/40). I think the TM10 was there somewhere, but I'm kind of guessing; I don't think it was next to the drive, but it might have been. Jnc (talk) 20:34, 12 April 2021 (CEST)
Ah, looking at that image, it's taken from just in front of the Ampex; you can see a corner of it. The RH10/DF10 are indeed in that corner; you can also see a bit of the RP04's behind them. The tape drive would be behind the camera; too bad we don't have a shot in that direction. Jnc (talk) 21:51, 12 April 2021 (CEST)
Very interesting, thanks! I suggest copying your comment to File_talk:Mit-mc.jpg. Larsbrinkhoff (talk) 20:58, 12 April 2021 (CEST)
Probably Talk:Incompatible Timesharing System would be better. I'll move the whole thread there. Jnc (talk) 21:51, 12 April 2021 (CEST)