On 28 Mar 2003 at 11:58, James Miller wrote:
>I recently ran across a junked item in the hall of my department at the
>university that I just couldn't pass up. From all appearances, it was an
>external hard drive. It's called a "Photon 20." It's in a metal box about
>1 foot square and 3 inches deep, with two ports on the back for, I guess,
>some sort of SCSI cable (similar to a printer cable [NOT the db 25 end],
>but wider: what's that cable called, by the way?). When I got it home I
>took it apart and, sure enough, it has a hard drive in it - a Seagate
>ST-225. An internet search reveals that this is an old, tried and true
>20MB drive (info on this drive at http://www.redhill.net.au/d-a.html ). I
>guess this device was supposed to allow data sharing between
>2 non-networked personal computers.
>From your description, it sounds to me like it is an external SCSI
drive case. Typically, these units have (on the rear of the case) a
standard power plug, a SCSI ID selector, and two Centronics 50-pin
connectors. These are similar to printer ones, but the printer ones are
36 pin. In both cases, about half the lines are dedicated to be ground
lines.
Have a look at the drive. If it is actually an ST-225N, then it is a
SCSI version of the drive. If it's an ST-225 or ST-225R, then it's an
MFM or RLL version of the drive, respectively. All three versions had
the same mechanics and platters, but different circuit boards - this
was very common for Seagate.
> The drive seems to work since, when
>I plug the thing in and turn it on the drive clearly spins up. This thing
>weighs a ton made, as it is, entirely out of heavy gauge sheet metal. It's
>in good shape. Probably costed a small fortune in its day. Apart from
>curiosity about what's on the drive, I have no real use for this piece of
>equipment. Maybe it belongs in a PC museum? I have no idea how common
>these were: it's made by "Warp Nine Engineering" in Roseville, MN.
Probably the manufacturer of the sheet metal box, perhaps the assembler
of the unit.
>I thought this might spark some nostalgic discussion around here. BTW,
what
>sort of cable would I need for this thing? I'm guessing it would plug into
>an LTP port on one end at the back of the computer. Is that correct?
>
>James
You'll will need a SCSI host adaptor (controller) card installed in the
computer. 8-bit and 16-bit ISA ones can sometimes be found in the used
parts bins in local computer shops, but it can take some hunting.
Often, cheap SCSI cards were used to connect early scanners, since the
SCSI connection gave a high data rate, and the same scanner could be
used for both Macintosh and IBM-type computers. Particularly be on the
lookout for ones manufactured by Adaptec - these are well supported
with drivers for most OSes.
You'll also need the appropriate cabling. Depending on the card you
get, you'll need either a SCSI-1 50-pin Centronics connector on both
ends, or a Centronics connector on one end, and a DB-25 connector on
the other. Some SCSI cards used an external 25-pin interface... Cost
of the cable shouldn't be more than $15 or so.
Finally, you may need a terminator. SCSI is absolutely insistent upon
having a terminating resistor set on each end of the SCSI chain of
drives and host adaptors. Typically, this looks like a small hunk of
plastic, with a 50-pin Centronics connector sticking out one side of
it. Usually, the last drive in the chain has the terminator plugged
into one of the two connectors on the back of the box (when using
external SCSI drives). Some drives have terminators built in, which
may need to be enabled/disabled for proper operation. Most host
adaptors have built-in terminators, which may need to be disabled to
use the external SCSI port.
I myself use SCSI drives all the time at home and work, and while many
people have complained that they are too complicated, it's not much
more so than selecting master & slave for IDE.
1. Set SCSI ID # for the drive. SCSI ID # go from 0 to 7 {SCSI I}, and
the host adaptor has its own #. No two drives can have the same number.
2. Connect the cables.
3. Check that there is a terminator at both ends, and no terminators in
the middle of the chain.
4. Check the termination again. :-)
5. Power up.
I'm fond of using the older SCSI drives in my SurvPC, for speed and
reliability. Once you've run a SCSI drive the first thousand hours or
so, most will keep running until the bearings wear out, since most were
built for servers - to run 24/7 for several years.
Hope this helps,
Anthony J. Albert
===========================================================
Anthony J. Albert [EMAIL PROTECTED]
Systems and Software Support Specialist Postmaster
Computer Services - University of Maine, Presque Isle
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