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From: jeh@dcs.simpact.com
Newsgroups: sci.electronics
Subject: Re: Dec Drive Mystery
Message-ID: <1991Apr1.110011.2244@dcs.simpact.com>
Date: 1 Apr 91 19:00:11 GMT
References: <140@w2xo.pgh.pa.us> <1991Mar31.223248.2242@dcs.simpact.com>
Organization: Simpact Associates, San Diego CA
Lines: 42

In article <1991Mar31.223248.2242@dcs.simpact.com>, jeh@dcs.simpact.com writes:
> 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.  ...

Credit where credit is due:  The above information (which I posted) is from
Terry Kennedy @ St. Peters' College.  On DECUServe there is a whole thread
devoted to making non-DEC drives behave as RDxx and similar, which Terry 
started.  Following my sig is his note on the RD53.  

	--- 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

            <<< EISNER::DUA3:[NOTES$LIBRARY]HARDWARE_HELP.NOTE;1 >>>
                               -< HARDWARE_HELP >-
================================================================================
Note 93.2         Low-end disk devices - The Digital difference          2 of 62
EISNER::KENNEDY "Terry Kennedy"                      25 lines  16-JAN-1988 01:37
                                   -< RD53 >-
--------------------------------------------------------------------------------
The DEC RD53 is a Micropolis 1325 or 1335 drive with one mod-
ification. Earlier units were 1325s, current units are 1335s.
The modification is as follows [yes, it will probably void 
your warranty]: Turn the drive over so that the logic board
is facing you. Locate the two slotted screws and loosen them.
Lift the drive logic board up gently (it is hinged). Toward
the hinge end, locate the empty location marked R7. Solder a
jumper in. You now have a RD53. You will need to move the
drive select jumper to either 3 (for DU0 or expansion cabinet)
or 4 (for DU1).

One word of caution - if you are re-using your old drive's
skid plate (the slide mount bracket), be sure to tape over
the metal on the front end of the bracket or it will short
out the drive. DEC's RD53 skid plates have foam covering the
metal.