[t13] T10/04-262r0

Pat LaVarre p.lavarre at ieee.org
Fri Aug 13 08:06:53 PDT 2004


This message is from the T13 list server.


>> > Every ATA read/write command specifies
>> > transfer length and data direction already.
>> > No need to store or derive that information elsewhere.
> >
> > Ah, for vendor-reserved commands, yes it would need specification.
 >
 > We want SCSI to be a blind  tunnel to the ATA device.
 > The bridge should not look at
 > the command code, sector count, or any other part of the register set.
 > This is what makes it work
 > for standard and vendor specific ... also ... new commands

Ouch, yes.

Always we should speak of wanting a transparent bridge because 
"vendor-specific and newly standard" ops break an opaque bridge, not 
just that the "vendor-reserved commands" break an opaque bridge.

Of course, a new data transport will break even a transparent bridge.  
We saw this recently, for example, when we added 48-bit LBA's to 
USB/ATA bridges that knew only 28-bit LBA's, also when we added UDMA 
thruput to USB/ATA bridges that knew only PIO.

Pat LaVarre




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