Command queuing and SAM - Correction and addendum.

Charles Monia, SHR3-2/W4, 237-6757, 11-Feb-1994 1532 monia at
Fri Feb 11 12:32:02 PST 1994

>From Jum McGrath's reflector note regarding command queuing:

>>                      Subject:                              Time:  2:55 PM
>>  OFFICE MEMO         Command Queuing and SAM               Date:  2/8/940
>>Is it required by SAM that any SCSI protocol support all of the traditional 
>>queuing functions (e.g. head of queue, ordered, abort, clear queue, etc...). ?  
>>It would be a goodness if only unordered queuing and some abort function 
>>anyone) be required.

My reply stated in part:

>Although support for queuing is still optional in SCSI-3, SAM requires
>that all SCSI-3 devices which implement queuing support all forms as well as
>the specified task management functions.

The above statement is incorrect. I had assumed that the working group consensus
reached at the last meeting (see X3T10/94-043R0, item 6) specifying that queuing
support was optional, implied that the SCSI-2 implementation rules were in 

It is my opinion that, strictly speaking, this is not the case. Furthermore, I 
see nothing in the original queuing document ( X3T9.2/91-098R6) passed
by the committee that implies otherwise.

>BTW: I would question why ATA should be bound by the rules that apply to 

I am told that ATA(PI) is to be added as one of the SCSI-3 protocols. If that
is the case, then, in my view, ATA(PI) must comply with SAM. Whether this
is desirable or not is, of course, for the committee to decide.

Charles Monia
SAM Technical Editor

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