[Info-vax] DLT drives and antique SCSI compatibility

[Dave Froble]

On 7/16/2020 2:49 PM, Arne Vajhøj wrote:
> On 7/14/2020 3:35 PM, Bill Gunshannon wrote:
>> On 7/14/20 12:58 PM, Stephen Hoffman wrote:
>>> And the Q-bus boards and drivers I was working on then ran afoul of
>>> the KFQSA, but that's DSSI and not SCSI, and the KFQSA is all fodder
>>> for another discussion.
>>>
>>> For various at DEC, DSSI was preferred to SCSI as it was multi-host
>>> and multi-initiator capable, viewed as better-specification, and was
>>> DEC-proprietary hardware, etc.
>>>
>>
>> I remember reading somewhere (back in the days when I was actually
>> using DSSI) that DSSI was considered SCSI done right.  At least in
>> DEC circles.
>
> Well - very late 80's and very early 90's then I think DSSI was
> better than SCSI. MicroVAX-disk tower-MicroVAX was pretty cool.
>
> But as usual:
>   higher volume => more revenue => more investment => more development
>
> Arne
>

Things change, and what's rather good at one time just isn't so 
important at a later time.

The 11/780 CPU was I believe 4 boards.  Large boards.  Maybe 16-18 
inches on each side.  Yu wanted multiple CPUs, you got multiple large 
cabinets.  (Not counting the 11/782.)  You got the star coupler to join 
multiple boxes to the same storage.

DSSI was a method at the time to allow multiple boxes (which then used 
CPU chips) to share the storage.

Today we have multiple cores on one chip, and multiple sockets on a 
single motherboard.  A lot more CPUs accessing storage without all the 
star coupler or DSSI bells and whistles.  And SAN storage.

It's my guess that some of what DSSI could do might still be useful, 
but, as mentioned, there might not be the volume to support specialized 
equipment.

Think about it for a bit and one will realize there was all kinds of 
good ideas in the past.  Including Alpha ....

-- 
David Froble                       Tel: 724-529-0450
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