Draft Minutes of T10 Plenary Meeting #20 - 3/13/9

John Lohmeyer John.Lohmeyer at symbios.com
Wed Mar 26 09:01:54 PST 1997

* From the SCSI Reflector (scsi at symbios.com), posted by:
* John Lohmeyer <John.Lohmeyer at Symbios.com>
At 03:59 PM 3/25/97 -0800, Jim Mcgrath wrote (in part):
>     One thing was discussed that could be interpreted as a protocol issue
>     and could contribute to the driver discussion is an attempt to
>     introduce a false (i.e. not counted) transistion at the beginning of 
>     a burst to overcome the problem of cleanly switching the lines for the
>     first transition after a long period of no transitions.  I'd hope that
>     the working group will consider ideas like that as well as purely
>     physical layer changes, since I'd like to avoid a transceiver change
>     if some minor work in the protocol could fix the problem.

Yes.  Such ideas (and several write precomp schemes) are definitely up for
consideration.  However, I should also point out that the first pulse
problem is not associated with driver types.  This problem is a cabling
phenomenon that occurs with either symmetric or asymmetric drivers.  We
will have to deal with this issue in Fast-80 regardless of what we decide
about symmetric drivers.

I think some people at the last meeting came away with the mistaken
impression that switching to symmetric drivers would solve the Fast-80
first pulse problem.  I think the benefit (if any) of switching to
symmetric drivers occurs at much higher frequencies.  The reason I say 'if
any' is that the data presented at the last meeting obviously used a single
vendor's parts.  It is not clear whether this data represents a benefit
inherent to symmetric drivers in general or just their design.


John Lohmeyer                 E-Mail: john.lohmeyer at symbios.com
Symbios Logic Inc.             Voice: 719-533-7560
4420 ArrowsWest Dr.              Fax: 719-533-7036
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