Command Queuing and SAM

Charles Monia 09-Feb-1994 1633 monia at starch.enet.dec.com
Wed Feb 9 13:32:47 PST 1994


You Wrote:

>
>                      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 (reset 
>anyone) be required.

>The reason I am opening this is because of ATA command queuing, where I want to 
>develop a very simple solution.  Functions other than unordered are either 
>useless or can be emulated by the host (i.e. just send down commands one at a 
>time for ordered commands).  This simplification should help in making queuing 
>easier for ATA implementations.
>
>Feedback is appreciated.
>
>Jim

Hi Jim:

The following is my personal opinion on the issue:

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.

BTW: I would question why ATA should be bound by the rules that apply to SCSI-3.

Thanks,
Charles
==============================================================
Charles Monia
C/O:
Digital Equipment Corporation
334 South Street
Shrewsbury, MA 01545

Tel: (508)841-6757		Email: monia at starch.email.dec.com
Fax: (508)841-6100





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