Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.2 8/7/84; site ucbvax.ARPA Path: utzoo!watmath!clyde!cbosgd!ucbvax!info-vax From: info-vax@ucbvax.ARPA Newsgroups: fa.info-vax Subject: Re: Unibus Disks Message-ID: <3359@ucbvax.ARPA> Date: Sat, 17-Nov-84 13:19:01 EST Article-I.D.: ucbvax.3359 Posted: Sat Nov 17 13:19:01 1984 Date-Received: Sun, 18-Nov-84 04:53:22 EST Sender: daemon@ucbvax.ARPA Organization: University of California at Berkeley Lines: 41 From: Richard Garland DEUNA, UDA50 and second Unibus: No you don't need a second Unibus! One BA11 box can supply 64 amps (50 amps on old models). You can string 2 BA11 boxes on the Unibus easily. That's plenty of room for everything. Too many people think they need a second Unibus adatpter (DW780) whereas they could get by with a second BA11 box. Each BA11 box can accomodate 2 large backplanes and 1 small. Thats about 12 hex slots and 4 quad slots per box. Constraints are total DC power (32 amps each half box) bus loads (22 max on whole bus - each interface is usually 1) total Unibus length (50 feet I think) and most important - system performance. Placement of interfaces on the bus, and bus interrupt levels must also be considerred. We have a working system (I wouldn't say it flies - but it goes OK) with the following: 1 LP11 6 DZ11's (48 lines) 1 DUP-11 1 DMF-32 1 DMR-11 1 DEUNA 1 UDA50 1 FPS164 interface (large array processor)ans 1 Evans and Sutherland PS330 interface This stuff is spread over 2 BA11 boxes on 1 Unibus. The system runs VMS and runs OK as I said. I plan to consolodate the 6 DZ11's into 3 Able boards when we get the funds. At least DZ11's needn't be considered by new installations. The main thing is - Consider a second BA11 box before considerring a second Unibus adapter. DEC sales sometimes forgets this option. Rg -------