Subject: Re: Configurating DSSI drives on MicroVAX 3400 (and 3300)
To: NetBSD Bob <>
From: Chuck McManis <>
List: port-vax
Date: 10/09/2000 14:27:53
At 05:19 PM 10/9/00 -0400, NetBSD Bob wrote:
>I have a question.   A list member passed me an RF35 drive for testing.
>It is loaded on my MV3300.  But, when installing the drive, I noticed that
>the label said ``RF35/RZ35''.  What does that mean, specifically?
>That sort of smells like an RF drive is really a SCSI drive?

What it means is that DEC sold two different "bottom plates" on the same 
drive mechanism, one was SCSI and one was DSSI.

>What exactly is different between RF and RZ drives?

One uses the SCSI protocol and the other uses the DSSI protocol for 

>Why cannot you use an RZ drive on a DSSI bus?

Because they are different protocols, both electrically and logically.

>What is the thing with the 4 prong vs 5 prong power connectors?

Makes it kind of hard to accidently screw up by putting a DSSI drive into a 
SCSI slot doesn't it?

>Can someone explain what is going on here?

DEC originally propagated their own "best" technology for disk (and 
system!) interconnects called DSSI. The world went SCSI. DEC needed to 
support both, but why stock two kinds of disk drive when you can just slap 
on the appropriate PCB at the last moment. More efficient for inventory.