Any interest in the PDP-1D timesharing CLK IOT?

[Bill E]

It provided a readable 1khz clock counter, an interrupt every 32msec, and one every 60secs. It's a simple device, but documentation is scarce.

All I know is the above and that it's IOT32. The few documents say the only visible state is the clock counter. I don't know how the interrupt channels were assigned, if it could be enabled and disabled, etc. It would be needed for the BBN timesharing implementation.

Bill

[Unibus]

Hi,

Out of curiosity I went hunting for info on PDP-1 timesharing. This may or may not be of interest to the Group. 

• Refer to Bitsavers for PDP-1D drawings series
  :-
• PDP-1D Serial Number 45 - BBN
• PDP-1D Serial Number 48 - Stanford University

The PDP-1D clock is detailed on the BBN engineering drawing 05601_BS_D-1D-45-56_1of1.TIF alternatively on Stanford 02901_BS_D-1D-48-29_1of1.TIF What I couldn't find were details of the oven and circuitry for the 1kHz crystal controlled oscillator Model-VO-547A. A crystal in a temperature controlled oven would have been the highest stability, 1 kHz sine wave source commonly available in the 1960s. I'm assuming sine wave output given it is fed via coaxial cable to a Schmitt trigger i.e. 4010 Logic Block. 

Channel Priority including the 32ms and 1 minute clocks is shown for BBN on 01701_BS_D-1D-45-7_1of1.TIF and Stanford on 01701_BS_D-1D-17_1of1.TIF circuits. Interesting to see Priority of the 1 minute signal is treated at different priority levels. Also there were many other significant Channel Priority differences BBN and Stanford.

Oscar may have to rework the Peripheral Panel and LED driving circuit to match 00301_MADE-1D-48-3_1of1.TIF while for completeness there was the panel 00301_MADE-1D-48-3_1of1.TIF

Implementation of time sharing would require expansion of the simulator to support configuration of a PDP-1D. References were:-

• Requirements for timesharing i.e PDP-1D
• PDP-1D-45 Supplement
• PDP-1 Options for PDP-1D e.g. Clock, instructions, etc.

Looks like a significant amount of work on expanding the simulator moving from a PDP-1C to PDP-1D versions to support timesharing.

If you were implementing the Clock there may need to be a BBN/Stanford University configuration switch for software from the different sites. Not an issue if only configuring for the BBN site. I'm clueless about the PDP-1 simulator so I'm not much help.

Regards,

Garry

--
You received this message because you are subscribed to the Google Groups "[PiDP-1]" group.
To unsubscribe from this group and stop receiving emails from it, send an email to pidp-1+un...@googlegroups.com.
To view this discussion visit https://groups.google.com/d/msgid/pidp-1/e645f335-4c56-4e4e-b018-30d982dfc12bn%40googlegroups.com.

[Bill E]

It seems a lot of the -1D mods were semi-random and of course the -1X was bonkers. Well, I implemented the clock because I need a periodic interrupt for some other stuff I'm writing.

To get around the differences, I extended the functionality by adding another non-standard bit, IOT 2032 lets you enable/disable the clock, enable/disable the 32msec and 1min interrupts, and specify the channels to use for each. It's all checked in. No flaming about the 'purity' of the original, since it wasn't pure to begin with. :)

Bill

PS - the simulator already implements some of the -1D functionality, but not all of it, such as the ring extensions.