Talk:IMP interface

DR11C

Re DR11C. I peeked at the driver in 2.11BSD and I think it said Unibus. But it was only a brief glance. Larsbrinkhoff (talk) 10:11, 15 March 2018 (CET)

Hey, this mentions UNIBUS:

• https://www.retro11.de/ouxr/43bsd/usr/man/cat4/css.0.html

Larsbrinkhoff (talk) 10:19, 15 March 2018 (CET)

Huh? That page talks about the IMP11-A, the DEC CSS thing.

Anyway, for the SRI thing, it was possibly both, actually. What it was was an SRI board that took the bit-stream from the IMP, doing the host-IMP harware protocol ('there's your bit', etc), and converted it to words, which it shipped over a parallel interface to a standard DEC DRV11 card. I'm pretty sure the QBUS DRV11 and UNIBUS DRV11-C had the same parallel port spec, so you could probably have plugged the SRI card into a DR11-C instead of a DRV11. Since the DR11-C/DRV11 are programmed I/O, they wouldn't have had the performance of the others, which were DMA, which is probably why UNIBUS machines tended to go with the DEC/ACC interfaces. Jnc (talk) 15:55, 15 March 2018 (CET)

Sorry, wrong link. This is better:

• https://www.retro11.de/ouxr/211bsd/usr/man/cat4/sri.0.html

Yes, I see now DR11-C is the name of a parallel interface. The BSD drivers use the Unibus device to talk to the IMP interface.

Here's a manual for the IMP interface:

• http://www.dtic.mil/dtic/tr/fulltext/u2/a037212.pdf

Larsbrinkhoff (talk) 08:36, 16 March 2018 (CET)

Right. And here is the 2.11 driver:

• http://minnie.tuhs.org/cgi-bin/utree.pl?file=2.11BSD/sys/pdpif/if_sri.h
• http://minnie.tuhs.org/cgi-bin/utree.pl?file=2.11BSD/sys/pdpif/if_sri.c

Looking at the driver, I'm not sure I understand how it works; it looks like it might loop in the interrupt handler, reading the entire packet? Eh, not important.

Somewhere I have MOS operating system drivers for it.

Also my memory was a bit off - it was byte at a time, not word at a time. Jnc (talk) 15:14, 16 March 2018 (CET)

Dynamic Modeling

MIT-DMS wasn't a typo. Although the situation is confused with many different names over the years (DMCG is another prominent one), I believe the official ARPANET name was MIT-DMS.

Here's a line from a 1980 MIT hosts list:

HOST MIT-DMS,           1/6,SERVER,ITS,PDP10,[DM,MITDM,MIT-DM,DMS]

So MIT-DM and plain DM were acceptable aliases. Other lists, e.g. https://github.com/ttkzw/hosts.txt, only says MIT-DMS with no aliases. Larsbrinkhoff (talk) 05:32, 21 October 2021 (CET)

We always called it plain 'DM', and a lot of software called it that, too - e.g. MLDEV. (IIRC, there was a directory which held binary for loadable devices, so when you referenced 'XXX:AAA; BBB CCC' it went and looked there for the correct file for XXX - the filename format and directory escape me at the moment - but you could look at a dump and see if there's a 'DMS' entry there, as well as 'DM'; they were actual files, so the dump would have captured them.) So that's why I changed it (my only goal is maximum accuracy), but I don't have any major commitment to using 'DM'; if you feel that 'DMS' is more accurate, feel free to change it back. Jnc (talk) 13:22, 21 October 2021 (CEST)

The file names for loadable devices are "DEVICE;JOBDEV xxx" where 'xxx' is the device name.

But while looking for that, in SYSDOC;ITS RECENT I found this:

Date: Fri, 28 Mar 86 09:02:47 EST

From: Alan Bawden

All kind of worms are crawling out of the woodwork because of various programs that -know- that all ITS machines are named "AI", "MC", "ML", or "DM".

which matches my memory (above). Jnc (talk) 16:41, 21 October 2021 (CEST)