On Sat, 11 Mar 2000, Michael Kukat wrote:

> Hi !
> 
> This ra* is for MSCP drives. My DSSI drive on a KFQSA in a VAX 4300 is also
> called "ra0". SCSI disks in VAXstations have their own controller, they are
> known as sd*. If SHAC support really becomes true, the drives just hang on a
> controller, similar to the SCSI chip in the VAXstations. The name for those
> drives should be defined, but it will neither be sd* nor ra* in this case,
> because this DSSI bus is a new bus connected to a controller chip. Just compare
> this with SCSI, AFAIK, DSSI is not that different from SCSI.

but DSSI disks _are_ MSCP devices. look at how VMS and ultrix treat them. 
A DSSI disk is exactly the same thing as an HSC with a single disk 
attached to it. Those all speak MSCP. DSSI is just a subset of the CI 
protocol over which MSCP is spoken. instead of the MSCP-talking 
controller being in a separate card (as in, for example, an RQDX and RD5x 
combo), the MSCP-talking logic is right on the same assembly as the disk, 
which is why DEC called them 'independent storage elements'. DSSI disks 
should just be ra*. SHAC is a CI adapter shrunk to a single chip. Look at 
the VAXclusters done over DSSI. It is CI. Use the source, luke!  DSSI is 
just a form of CI with no star coupler! it is _electrically_ similar to 
SCSI: the pin assignments are very similar, signal levels and so on are 
just about identical, but the protocol spoken is totally different- it's 
MSCP. 

Isildur