12 Oct
2022
12 Oct
'22
9:38 p.m.
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
here:
http://gunkies.org/wiki/Category:DEC_Synchronous_Serial_Interfaces
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.
Noel