esdi hard drive identification

From: <(>
Date: Sat Sep 4 17:26:16 1999

>One of the surplus stores in my area just got in a load of 5-1/4 form factor
>hard drives. They look just like the ones my PDP-11/73's use (RD51 or 52,
>can't recall). I believe my controller is a RQDX2, not a RQDX3. My drives
>are 30mb.

If they're for use with a RQDX2 or 3, they'd better be MFM (ST-506)
interface drives, not ESDI drives! The connectors are the same, but
the signals are quite different.

>I was wondering, is there an easy way (short of looking up the model
>numbers) to visually determine if any of the drives are ESDI and might work
>with my 11/73?

Most any ST506 drive can be pressed into use with a RQDX1/2/3, with
an appropriate low-level format (via XXDP's ZRQB?? or ZRQC?? formatter).

The RD52 is a Quantum Q540 or an Atasi AT3046. Capacity around 30 Mbytes.
There was also a CDC drive used, I'm not sure what the model number was.

The RD53 is a Micropolis 1325 (early ones) or 1335 (later ones). Capacity
around 65 Mbytes.

The RD54 is a Maxtor XT2190. Capacity around 140 Mbytes. Won't work with
a RQDX1/2, only a RQDX3.

If you're really interested in pursuing the use of random MFM drives
on your RQDX2 or RQDX3, pay close attention to the notes that Terry
Kennedy has kept in

for the past decade or so. There are many details about the use of
non-DEC-branded-drives, and in particular there are some suggestions for
formatting them with XXDP.

 Tim Shoppa                        Email:
 Trailing Edge Technology          WWW:
 7328 Bradley Blvd		   Voice: 301-767-5917
 Bethesda, MD, USA 20817           Fax:   301-767-5927
Received on Sat Sep 04 1999 - 17:26:16 BST

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