On Thu, Jan 18, 2018 at 10:27 AM, Noel Chiappa via cctalk < cctalk@classiccmp.org> wrote:
> > From: Grant Taylor > > > The ARPANET supported several different kinds of interfaces between the > IMPs > (the switching nodes in the ARPANET) and hosts, but the 'usual' one was > either 'Local Host' (LH) or 'Distant Host' (DH) which were _basically_ > identical except at the very lowest level - LH was TTL, and DH was > differential pair. > > Those interfaces were a custom bit-serial thing with a handshake (with > "there's-your-bit", "ready-for-next-bit" lines, etc); see BBN Report #1822: > > And an "end-of-packet" bit. > http://www.bitsavers.org/pdf/bbn/imp/BBN1822_Jan1976.pdf > > So the "ARPANET interface" in the host is a piece of custom hardware (some > were DMA; I also used one which was interrupt per byte) which went on the > host, which talked 1822 (as it was called), of either the DH or LH physical > form. > > > > > Do the necessary emulators support the ARPANET interface? > > Dunno, but they shouldn't be too hard to add. > > The real problem is going to be 'what do you hook the simulated ARPANET > interfaces up to, and how'? I know they have IMP code running in > simulators: > > http://mailman.trailing-edge.com/pipermail/simh/2013- > November/007672.html > > but I dunno how one would hook _that_ simulation up to a simulated host > running a simulated ARPANET interface. > > The IMP emulator emulates the DH/LH interface with UDP packets. I wired up the dps8/m emulator to the IMP emulator, but I don't have the ARPAnet stack for Multics, so it's just packets. -- Charles
