FW: Should there be a bit in INQUIRY Data for Fast-20?

Skip Jones sk_jones at qlc.com
Fri Aug 26 02:48:53 PDT 1994


Since Gerry is absolutely correct regarding this issue, I, of course, fully
agree with him.  Besides, if someone writes firmware that does not know how to
handle an attempt to be negotiated faster than the rate supported, then he or
she deserves a nasty surprise!

skip jones
_______________________________________________________________________________
From: Gerry Houlder on Fri, Aug 26, 1994 10:39 AM
Subject: Re: Should there be a bit in INQUIRY Data for Fast-20?
To: scsi at wichitaks.ncr.com

John lohmeyer wrote:
 
>Should we add a bit to the INQUIRY Data to say the target supports Fast-20 >to
avoid any nasty surprises?
>
No, we shouldn't. The synchronous rate negotiation rules are pretty clear
(about as clear as anything ever gets in SCSI) and they work correctly across
asynchronous, slow synchronous, fast synchronus, fast-20 synchronous, and
fast-40 synchronous. The only occurrances of "wrong synchronous transfer rate
agreement" have always been firmware or hardware bugs that were acknowledged
and corrected by the vendor. This kind of thing happens with early versions of
new products but I can't believe anyone has production version disk drives with
this kind of problem. Another bit in INQUIRY wouldn't have prevented such
problems.
 
How many initiators use the existing "synchronous transfers supported" bit to
determine if synchronous negotiation should be attempted with a particular
drive? None that I know of. Initiators that want synchronous simply initiate
the negotiation and take whatever rate thay can get.
--
Gerry Houlder -- Gerry_Houlder at notes.seagate.com
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### OGATE Version 8 message trace and attachment information:
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### Org Date:    08-26-94 06:37:41 AM
### From:        Gerry Houlder at SEAGATE
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### Subject:     Re: Should there be a bit in INQUIRY Data for Fast-20?
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