Response to SPI-4 proposal 01-251

Bill Galloway BillG at
Thu Aug 30 18:10:27 PDT 2001

* From the T10 Reflector (t10 at, posted by:
* "Bill Galloway" <BillG at>

I had to go all the way back to SPI to find the words I remembered:

The target PIA shall generate REQx pulses independent of the ACKx pulses
until the REQ/ACK offset is reached.  The initiator PIA shall generate ACKx
pulses independent of the REQx pulses until the number of ACKx pulses equals
the number of REQx pulses detected.

NOTE the word independent. These words were put in to keep either the target
or initiator from saving up REQs/ACKs before sending them.

I just assumed(BAD IDEA) that these words or something similar were still
there. If both the target and initiator hold back REQs/ACKs and use a
different algorithm you can have a deadlock. Without something similar these
words you can have a deadlock.

I know these words do not currently apply to SPI-4 but I think you are still
running a risk(very small). As we poor initiator guys know the target is in
the driver seat and what is not dis-allowed is permitted.  You could say the
same thing for the initiator but it is much more of a slave in the REQ/ACK

Bill Galloway
BREA Technologies, Inc.
P: (281) 530-3063
F: (281) 988-0358
BillG at

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