Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!csd4.milw.wisc.edu!uakari.primate.wisc.edu!indri!lll-winken!uunet!mcvax!ukc!servax0!rick From: rick@servax0.essex.ac.uk (Rick Blake) Newsgroups: comp.arch Subject: Re: DECSYSTEM 20 Message-ID: <1342@servax0.essex.ac.uk> Date: 28 Jul 89 09:56:35 GMT References: <3256@wpi.wpi.edu> <443@anasaz.UUCP> <20767@cup.portal.com> Sender: news@servax0.essex.ac.uk Reply-To: rick@essex.ac.uk (Rick Blake) Organization: University of Essex, Colchester, UK Lines: 26 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 DL10 was a DMA device that allowed a PDP-11 access to some portion of DEC-10 memory - indeed, we still have one :-). I don't believe that it was available on the DEC-20. It was typically used for interfacing PDP-11 comms front ends with a DEC-10. It would only handle 11/40s, but it was possible by a little tweaking of the hardware (in the -11) to get 11/34s to hang off it as well. In principle, it would take 4 -11s. Generally, the 11/40s on a DEC20 were interfaced through a device called a DTE, as (correct me if I'm wrong, someone) the DL10 needed an external I/O bus, which was not provided on the DEC-20. Rick Blake - University of Essex, Colchester, UK. JANET: rick@uk.ac.essex Internet: rick@essex.ac.uk UUCP: ....!mcvax!ukc!sx!rick