Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Path: utzoo!mnetor!seismo!ut-sally!pyramid!decwrl!johnsson From: johnsson@decwrl.DEC.COM (Richard Johnsson) Newsgroups: net.dcom Subject: Re: DEC DMV-11 and DMR-11 point-to-point link questions Message-ID: <6265@decwrl.DEC.COM> Date: Thu, 6-Nov-86 01:21:49 EST Article-I.D.: decwrl.6265 Posted: Thu Nov 6 01:21:49 1986 Date-Received: Fri, 7-Nov-86 08:57:01 EST References: <29@halleys.UUCP> Reply-To: johnsson@decwrl.dec.com (Richard Johnsson) Organization: DEC Western Software Lab, Palo Alto, CA Lines: 56 > is the Q-bus DMV-11 equivalent to the Unibus DMR-11? sort of. They are similar. The DMR is much more general and can go up to 1 megabit per second. The DMV is limited to 56K. For most normal purposes ther are functionally equivalent. > will they interoperate (will a DMV-11 talk to a DMR-11?) Yes. They both speak DDCMP (version 4 I believe). We have many talking to DMR's in the internal DEC network (all DECnet based). We haven't yet tried any in Ultrix. > is the DMV-11 program-compatible with the DMR-11? Not quite. I don't know the differences, but I have looked at the source for the DMV driver in Ultrix 2.0 and it says it was derived from the dmc/dmr driver. It is apparently different enough that putting in a few runtime conditionals was not reasonable. > How many DMR-11's can be installed on a single VAX? Mostly I think it depends on having enough Unibus power. They suck up a lot of +5 (about the same as a UDA50 which is about 12 amps for the two boards). I believe the power requirement limits you to four per BA11 box. Locally we have a VMS 750 in the internal network with 6 DMR's (4 @ 9.6 and 2 @ 56). We have an Ultrix 750 with 4 DMR's (2 each 9.6 and 56). > How many DMV-11's can be installed on a single MicroVAX? Our newly installed DECnet router microvaxen each have 5 DMV's. Corporate Telecom which runs the internal network approves of running one DEQNA and 5 DMV's @ 56K on a microvax (II of course :-) as a dedicated router. > I see no hard-limit in the dmc driver... Actually there's a bug in the Ultrix 1.2 dmc driver (which may have been propagated from or to elsewhere) which limits it to one: At line 389 (first executable line of dmcload()) change unit = (sc - dmc_softc)/ sizeof (struct dmc_softc); to unit = (sc - dmc_softc); Also there are some funnies in the handling of multiple point-to-point links (and point-to-point links in general) in Ultrix 1.2, BSD 4.2 and at least early versions of 4.3. I have sent the changes to be included in Ultrix 2.0 but haven't looked lately to see if they're in. Hope this helps. -- Richard Johnsson, DEC Western Software Lab, Palo Alto, CA UUCP: {decvax,ucbvax}!decwrl!johnsson ARPA: johnsson@decwrl.dec.com DEC ENet: rhea::johnsson phone: +1 415 853 6676