SUMMARY: newer SCSI drives in older Suns

From: Dan Simoes (
Date: Fri Oct 23 1998 - 13:59:54 CDT

I asked:

Searching the archives didn't turn up any answers (always a good
idea to look there first!) so here goes...

I'm looking to put some newer drives into a Sun clone,
equivalent to a SS10/20. These machines use a 50 pin,
narrow, fast scsi-2 interface, as best I can determine.

"Old" drives that work in these are for example the Seagate ST32550N
and ST32171N.

It appears that scsi-2 drives are no longer being produced and
everything out there is ultra scsi (the remaining scsi-2 drivers
cost a small fortune).

A vendor suggested that I could use the ST34520N drive, 4.55Gb,
SCSI-3 ultra. At $250 street price, it's a steal.

The question is, are all (or most) of the ultra drives
backward compatible with scsi-2? Also, if you've installed
these newer drives, have you run into any heat issues, since
these drives generally spin faster?

Summary: the general consensus is yes, you can.
One person had experienced some problems with timeouts.

It's clear that I need to get my hands on the drive first
and make sure the connectors are the same.
If I actually get anything to work, I'll post a followup.


| Dan |

Replies were:
From: Harvey Wamboldt <>

And, assuming you have a SCSI-2 controller that is reasonably close to
the spec, it should work.

> The question is, are all (or most) of the ultra drives backward
> compatible with scsi-2?

Yes, you simply have to match the interface style with what you want
to connect to to simplify cabling. Electrically a single ended Ultra
SCSI interface should "fall back" and be compatible with single ended
SCSI-2 and even single ended SCSI-1. You just have to get the
connectors, terminations, termination power, cable lengths, cable
widths, cable impedance, and controller configuration (AKA "scsi
options") correct. With special cables and terminators you can even
connect a narrow SCSI device on the end of a wide SCSI chain and if
you haven't violated length, termination, and impedance limits (and
you have a fully compliant SCSI controller) it should work fine.
Fortunately all you usually have to do is set a jumper on the drive to
disable built in termination and cable things up and every thing

problems are due to built in termination being used with external

Check out:


for more info.

> Also, if you've installed these newer drives, have you run into any
> heat issues, since these drives generally spin faster?

Yes, heat is a problem on larger, faster disks. Use an external
drive, ensure it has a good fan, room for air flow around the drive,
and clearance around the air intake and exhaust ports. For new
smaller drives of the same size and speed as older drives, I think
power consumption has gone down a tad since they are spinning less
mass and have slightly better bearings these days.

From: Rik Schneider <>

As long as you can get the right cabling for the drive and your power supply is up to the job you shouldn't have any problems.

Most of the current crop of drives run a quite a bit cooler than earlier drives of the same capacity. I am currently using an IBM 5400 RPM 2.3G drive in a SS-1+ in place of the original 3600 RPM 300M. The case is now cooler and the system draws less power at start-up.

-- From: Karl Vogel <> Newer drives generally run cooler than their predecessors, unless you're comparing something like a 10,000 RPM drive with a 2,400 RPM drive.

-- (lost headers) I've had no problems using a ultra drive in a SS2 clone (bear in mind that the transfer rate is no faster than 10mbps).

One thing worth noting:

Your drives will last longer if you keep them cooler. I redirected the airflow in my SS2 to blow around the drive (since I don't have SBUS cards) to help keep the drive cool.

The good thing about newer drives is that although they may run faster, I think they run cooler than the early 7200 rpm drives (like the barracuda). This is a good thing.

-- From: Bismark Espinoza <>

I have a SPARC2 with a scsi-3 boot disk ( sd3: <SEAGATE ST15150N cyl 3695 alt 2 hd 21 sec 108> ).

Every time I reboot and at other times I get a:

"esp0: Rejecting message EXTENDED 0x3 from Target 0" -- From: Sebastian Benoit <>

Transtec, Germany sells Ultra-SCSI drives for the SS10. They say in their product catalog that 1) There are no heat problems with the SCSI-drives with 7200rpm 2) Ultra-SCSI drives run at normal Fast-SCSI speed on controlers that dont support Ultra-SCSI. 3) They sell IBM and Seagate drives, check out

They sell the following for the SparcStation 10: Seagate Barracuda 9LP (ST39173N) IBM DGHS39100U IBM DDRS39130U Seagate ST39140N Seagate ST34572N Seagate ST34573N Seagate ST34520N IBM DDRS34560U

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