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- Path: sparky!uunet!stanford.edu!rutgers!spcvxb!terry
- From: terry@spcvxb.spc.edu (Terry Kennedy, Operations Mgr.)
- Newsgroups: vmsnet.pdp-11
- Subject: Re: Whats the difference among SMD drives?
- Message-ID: <1993Jan6.033939.4825@spcvxb.spc.edu>
- Date: 6 Jan 93 08:39:39 GMT
- References: <1993Jan6.035634.14405@mail.cornell.edu>
- Organization: St. Peter's College, US
- Lines: 37
-
- 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
-