Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!zaphod.mps.ohio-state.edu!think.com!ames!ucsd!nosc!crash!simpact!jeh
From: jeh@dcs.simpact.com
Newsgroups: sci.electronics
Subject: Re: Dec Drive Mystery
Message-ID: <1991Mar31.223248.2242@dcs.simpact.com>
Date: 1 Apr 91 06:32:48 GMT
References: <140@w2xo.pgh.pa.us>
Organization: Simpact Associates, San Diego CA
Lines: 18

In article <140@w2xo.pgh.pa.us>, durham@w2xo.pgh.pa.us (Jim Durham) writes:
> On a DEC RQDX2 disk controller, the controller 'knows' when you are
> using an 'official' DEC drive (RD52,RD53). [...]

I don't know about the RD52, but the RD53 is a  Micropolis 1325 or 1335 (DEC
has used both) with a wire jumper installed in the normally-empty "R7" position
on the PC board.  My company has bought a couple of these drives and run them
on RQDX2, RQDX3, and the integrated controller in a MicroVAX 2000.  (Note that
the RQDX2's format is different from the latter two.)

As for why other drives with identical geometry won't work, I can't say.  It
must have something to do with that R7 jumper.  Does anyone know what the
jumper does?

	--- Jamie Hanrahan (x1116), Simpact Associates, San Diego CA
Chair, VMS Internals Working Group, U.S. DECUS VAX Systems SIG 
Internet:  jeh@dcs.simpact.com, or if that fails, jeh@crash.cts.com
Uucp:  ...{crash,scubed,decwrl}!simpact!jeh