[TUHS] Attempting To Build NOSC and BBN UNIXs + ARPANET code

Noel Chiappa jnc at mercury.lcs.mit.edu
Thu Oct 13 05:38:56 AEST 2022

    > From: Michael Casadevall

    > sys4.c is entirely corrupted, and part of impio.c is cut off

The copy on MIT-CSR (the origin of the copy at TUHS) has the same issues. I
doubt it's possible to recover them from that system; you'll have to find
some other way to recover them (perhaps through a dump of the BBN system), or
re-code them (as you did with sys4.c).

    > I do need to do a readthrough for the VDH driver ... I think that might
    > be for the radio links to Hawaii and the UK? 

No. Read BBN 1822.

The LH and DH bit-serial physical interfaces only work up to about 1000 feet
or so. (Less for LH; DH is logically idential to LH, but uses differential
pairs - the LH is single-sided). VDH is, in the bottom layer, simply a
synchronous serial link, allowing the host to be up to hunreds of miles from
the IMP.

    > From: Lars Brinkhoff

    > Another it adding emulators for various IMP interfaces. I.e. you will
    > not get anywhere without adding one of IMP11A, ACC, or VDH to SIMH.

Did VDH PDP-11's have a special VDH interface, or did they simply use an
off-the-rack DEC synchronous serial interface like a DU11? (More of them


if anyone wants.) Looking at net_vdh.h, it seems to be a "VDH-11C"

Looking online, the VDH-11 seems to be an ACC prodict, but I wasn't able to
find anything out about it at all. (I have some hardcopy manuals for other
ACC IMP interface products, and I was going to look in them to see if any of
them listed its manual in a 'see also', but I can't find them.)

I'm not sure why people did just use an off-the-rack DEC synchronous serial
interface; maybe the VDH11 did a BBN specific CRC, or something (in addition
to using DMA; mostr DEC sync interfaces didn't, IIRC)?

Anyway, you don't want to use VDH.


More information about the TUHS mailing list