Extended Modes for Margining for READ/WRITE BUFFER

John Lohmeyer lohmeyer at ix.netcom.com
Tue Oct 27 10:22:15 PST 1998

* From the T10 (formerly SCSI) Reflector (t10 at symbios.com), posted by:
* John Lohmeyer <lohmeyer at ix.netcom.com>
At 10/23/98 03:38 PM, you wrote:
>* From the T10 (formerly SCSI) Reflector (t10 at symbios.com), posted by:
>* "Binford, Charles" <charles.binford at symbios.com>
>If the initiator detects an error the proposal says it is to send
>INITIATOR DETECTED Error message.  Is this message supposed to be sent
>on the same reselection as the data was delivered on?  With the
>automation most SCSI chips have today it seems the target would have
>disconnected and possibly started working on one or more other IOs
>before the Initiator has had a chance to process the completion
>interrupt and verify the data.


The target cannot disconnect before the initiator sends the INITIATOR
DETECTED ERROR message because the initiator silicon should assert the ATN
signal before the end of the DATA IN phase.  (Of course, this might be a
problem for initiator silicon automation, but the initiator software should
turn off the automation.)

>Also,  I'm assume this proposal is aimed at parallel SCSI.  However,
>under FC the INITIATOR DETECTED Error message is even more problematic.

Yes, this proposal is aimed at parallel SCSI.  I suspect that FC will have
to solve its domain validation issues (if any) with other tools.

>I'd suggest dropping the INITIATOR DETECTED Error message part.  What is
>the target going to do with it anyway?

I hope that the target does nothing with it today.  Eventually, however,
the target could use this message to optimize its transmit parameters.
That is, if it sees that certain margin adjustments cause errors and others
work well, it could change its default settings to always use the good
settings for that initiator.

By the way, rev 2 of 98-184 seems to have dropped the margin adjustment field.


John Lohmeyer                  Email: lohmeyer at ix.netcom.com
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