RQDX3 on an 11/23?

Fred N. van Kempen waltje at pdp11.nl
Wed Mar 16 10:16:00 CST 2005

On Tue, 15 Mar 2005, Ethan Dicks wrote:

> > > Do the drives for the RQDX3 have to be DEC drives or will any MFM
> > > drive do? It seems like ST225 drives are fairly easy to find.
> Yes they are, and yes, they will work without modification, as will ST-251s.
DEC used Seagate ST225 (RD31) and ST251 (RD32) drives, various
Seagate models for RD50 and RD51, three different vendors for
the RD52 drive, two for the RD53 (Micropolis and ?) and then
there's the RD54 (maxtor 2190) that comes in three flavors.

So.. although the *format* must be DEC, this has nothing to do
with the drive per se.  You can format an ST251 as usual, and
then "label" it as being an RD31.  This will waste space, but
other than that, it works fine.

> Yes it is.  The ST-251 formats up as an RD32.  Since they have fewer
The RD32 _is_ an ST251.

> heads than the full-height devices, they are not as fast (it's quick
> to switch heads, slower to move them), but they do work.  In the
This is true.. most (but not all) full-height drives are faster
than their same-capacity half-height friends, because of what
Ethan just explained.  The same goes for drives with more sectors
per track, obviously.  All this -does- depend on the drives,
though, its not a given.

> I have never used an RQDX3 except in a BA23 or BA123, but the schemes
> I've seen described in this thread to manufacture a direct RQDX3->hard
> drive should all work.  If you can lay your hands on a BA23, however,
Yes, you can make such a cable easily, especially if you're only
going to connect a single drive.  PeteD posted the howto on it.


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