Path: utzoo!attcan!uunet!fernwood!portal!apple!rutgers!njin!spcvxb.spc.edu!terry
From: terry@spcvxb.spc.edu (Terry Kennedy, Operations Mgr)
Newsgroups: comp.sys.dec
Subject: Re: MV II Hardware help
Message-ID: <1990Oct6.023655.585@spcvxb.spc.edu>
Date: 6 Oct 90 02:36:55 GMT
References: <8791@pitt.UUCP>
Organization: St. Peter's College, US
Lines: 43

In article <8791@pitt.UUCP>, jcd@pitt.UUCP (Jim Durham) writes:
> Second question: Does anyone know exactly what goes on with
> an RQDX2 controller and non-DEC drives. I have received several
> answers. One is that DEC writes a "descriptor block" out to the
> drive to tell the controller what kind of drive it is. Without
> this, according to this scenario, the formatter won't format
> the drive.

  Not on a '2, it doesn't. The RQDX1 and 2 write out (in addition to
the MSCP-defined stuff) the ROM version that formatted the drive and
the date. Period. These controllers rely on certain responses from
the drive in order to guess what drive type it is. You could certain-
ly change the drive tables in the ROM to do what you want, but that's
non-trivial.

  The '3, on the other hand, writes the complete geometry info onto
the disk.

> The other answer is that I need to change the
> mysterious 'R7'. What is 'R7' ? A jumper? A resistor. I need
> to know what it actually *does*, because, since I'm interested
> in using a non-DEC drive, it won't have 'R7' and I'll have to
> fudge a substitute. Does this have anything to do with tying
> write protect high thru a 1k resistor?

  Hmmm. You probably heard that from me, but it got garbled. R7 is an
empty position on a Micropolis 1325/1335 disk drive logic card. If it
was a real DEC RD53, it would have a zero-ohm resistor soldered in
there (instead of the nothing that's there [or is that isn't there 8-]
now). That only applies to RD53's. RD51's (Seagate ST-412's), RD52's
(Quantum Q540's or Atasi 3046's) don't need any changes. Note that the
RD53 is only supported on the RQDX2, but that RQDX2 ROMs work in an
RQDX1 (shhh... Don't tell anyone or the RQDX1 prices will go back up
at the used dealers 8-). The RD54 (Maxtor XT-2190), RD31 (Seagate ST-
225) and RD32 (Seagate ST251-1) are only supported on the RQDX3.

  If anybody wants to hear more about this, please followup here so
everybody else can see it - every time I post one of these I get *del-
uged* with mailed requests...

	Terry Kennedy		Operations Manager, Academic Computing
	terry@spcvxa.bitnet	St. Peter's College, US
	terry@spcvxa.spc.edu	(201) 915-9381