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From: alan@shodha.enet.dec.com ( Alan's Home for Wayward Notes File.)
Newsgroups: comp.unix.ultrix,comp.sys.dec
Subject: Re: DSSI disks
Summary: DSSI is not SCSI.
Keywords: dssi, disk
Message-ID: <3372@shodha.enet.dec.com>
Date: 14 Jun 91 00:30:33 GMT
References: <1991Jun13.200046.4932@mlb.semi.harris.com>
Followup-To: comp.sys.dec
Distribution: usa
Organization: Digital Equipment Corp. - Colorado Springs, CO.
Lines: 33

In article <1991Jun13.200046.4932@mlb.semi.harris.com>, jdr@sloth.mlb.semi.harris.com (Jim Ray) writes:
> Anyone know if the DSSI disks are SCSI ( or some form thereof )?

	DSSI is not SCSI, though at times it looks a lot like it.  First
	the storage protocols used are MSCP for disks and TMSCP for tapes.
	As with SCSI each "device" on it has an imbedded disk or tape
	controller.  The DSSI devices are called Integrate Storage Elements
	(ISEs).

	One way of looking at is that each ISE is a single drive HSC and
	the DSSI is the CI.
> 
> If not, what type of interface do they use?

	Yet another DEC proprietary DSA thing.  I suspect that people
	that designed looked at SCSI and decided they could do better.
	They probably use EDC/ECC instead of parity for data integrity
	on the bus.  They may have extended the 6 meter cable limit or 
	least made sure that all 6 meters is usable.

	If DSSI drives were closer to SCSI drives in price, I'd prefer
	them for storing my files.
> 
> Thanks,

	You're welcome.

> --
> Jim Ray                                Harris Semiconductor


-- 
Alan Rollow				alan@nabeth.cxn.dec.com