Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!mailrus!husc6!ogccse!blake!Tomobiki-Cho!mrc From: mrc@Tomobiki-Cho.CAC.Washington.EDU (Mark Crispin) Newsgroups: comp.arch Subject: Re: DECSYSTEM 20 Message-ID: <3055@blake.acs.washington.edu> Date: 1 Aug 89 20:30:18 GMT References: <3256@wpi.wpi.edu> <443@anasaz.UUCP> <20767@cup.portal.com> Sender: news@blake.acs.washington.edu Organization: Mendou Zaibatsu, Tomobiki-Cho, Butsumetsu-Shi Lines: 46 In article <20767@cup.portal.com> mmm@cup.portal.com (Mark Robert Thorson) writes: >With regard to the pdp-11 and the -10, I recall a puzzling fact from the >PDP-11 Peripherals Handbook. Out of a large collection of peripheral products >there was one which did not have "11" in its name. This was the DL10 >Unibus window. It was also unusual in that it might not return slave sync >for a ridiculously long time, like 30 seconds. > >I know DEC-20's used 11/40's as front end machines. Did they interface via >a DL10? Could someone briefly describe what services the 11/40 did? >(Or it might have been labelled 11/35 -- same set of CPU cards.) The DECSYSTEM-20 site prep documentation references the DL10, but only as the terminal lines for a KL10. There were really DH11's driven by the 11/40 front end. All KL10's had an 11/40 front end; I suspect that's what most 11/40's ended up being. On the DECsystem-10 the front end was the console processor responsible for booting and controlling the back end. On the DECSYSTEM-20, in addition to its console duties the front end controlled all the unit record devices: terminals (DH11), lineprinters (LP20 - a Unibus peripheral despite its name), and card reader (CD20). I think that, like the ARPAnet interface, the card punch and paper tape peripherals were on an I/O bus driven directly by the back end; only machines with such esoteric devices had back-end I/O busses. The console 11/40 ran a hacked-up version of RSX-11 called RSX-20F. There was elaborate code for each CPU to "keep alive" the other via a watchdog timer that would push the other CPU's boot button if it failed to keep it up to date. The very earliest KL10 systems used the field service diagnostic monitor for the 11/40 called KLDCP. KL10's could have up to three secondary 11/40 front ends called DN20's; generally these were DECnet synchronous line controllers. The KS10 used an 8080 for its console processor and had a Unibus adapter (UBA) to interface to the Unibus. It drove the peripherals directly with no front end help, modulo the KMC11 being a front end for a DUP11 in synchronous DECnet (the DN20's also used KMC11's to drive DUP11's; the combination was called "KDP"). Mark Crispin / 6158 Lariat Loop NE / Bainbridge Island, WA 98110-2020 mrc@CAC.Washington.EDU / MRC@WSMR-SIMTEL20.Army.Mil / (206) 842-2385 Atheist & Proud / 450cc Rebel pilot -- a step up from 250cc's!!! tabesaserarenakerebanaranakattarashii...kisha no kisha ga kisha de kisha-shita sumomo mo momo, momo mo momo, momo ni mo iroiro aru uraniwa ni wa niwa, niwa ni wa niwa niwatori ga iru