🚀 go-pugleaf

In article <1993Jan6.035634.14405@mail.cornell.edu>, jrl2@cornell.edu (Jeffrey Luszcz) writes:
>   I've seen many SMD drive for sale on the net.
> Whats the difference between a SMD drive used
> on a SUN and a SMD drive used with a pdp?
>   I would think it would be in the connector
> and cables...Iwould think the SUN types of connections
> would be wore modern and compact.

  SMD drives are SMD drives. Mostly. They all use a 60-pin common cable and
a 26-pin radial cable. The signals on the cables are the read/write data,
some state lines (like index) and a bus which is used for a variety of func-
tions (like head select, cylinder select, etc), along with tag lines which
identify which function is currently in progress on the bus lines.

  Early SMD drives were large floor-standing units (typified by the CDC
9766, also known as the DEC RM05). Newer units still used removable packs,
but were smaller and rackmountable (like the Calcomp/Century Data Trident
family). Finally SMD drives became sealed-media Winchester-type drives.
The most-recently-produced units I know of are the CDC 9720 family, which
come in sizes up to 1.8Gb (unformatted). Two of these fit side in 1 19"
rack.

  The main difference between the old drives and the new ones (in terms of
the interface) is the data rate. Obviously the newer drives pack more bits
per revolution, so the data rate is higher (since lowering the speed of ro-
tation isn't productive). There is also extended cylinder addressing to
allow for more cylinders, and extra tag functions for new commands related
to error recovery, etc. Most controller/drive combos will ignore any tags
the counterpart doesn't support.

  So, provided your controller can support a data rate higher than or equal
to that of a drive you want to connect, it should work. I've seen 9766's
on some pretty new controllers (ever see a 9766 known as DUA0:? 8-).

	Terry Kennedy		Operations Manager, Academic Computing
	terry@spcvxa.bitnet	St. Peter's College, Jersey City, NJ USA
	terry@spcvxa.spc.edu	+1 201 915 9381