>> Domain validation covers two cases. You are referring to a system
>> that does not work as specified. The other case for domain
>> validation is to support legacy equipment, which still has
>> economic value, but cannot run reliably at the fastest SCSI rates.
>
>Every device negotiates its data transfer speed independently with the host
>using WDTR, SDTR, and PPR messages. Legacy devices never even try to run
>faster than their maximum speed that is fixed at the time the device is
>manufactured. Legacy devices aren't affected by other devices running at
>faster speeds, because at any time the bus is only controlled by a single
>target and initiator. All other targets just stay off the bus and don't care
>about what data rate is used by the target and initiator that happen to
>currently control the bus.
I agree with all that you've said, but you've left out the most compelling
reason that domain validation is necessary: SCSI->SCSI bridges. Although
a SCSI-SCSI bridge may support some LVD transfer speeds, it may not support
all of them. The only way to find out is to perform domain validation.
For instance, I have no idea if the currently available LVD->SE/LVD bridges
understand DT transfers.
--
Justin
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