From owner-freebsd-hackers  Sat Aug 15 11:58:49 1998
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To: Mike Smith <mike@smith.net.au>
Cc: hackers@FreeBSD.ORG
Subject: Re: TESTERS WANTED for new ATAPI CD/CDR/CDRW driver. 
Reply-To: Jason Thorpe <thorpej@nas.nasa.gov>
From: Jason Thorpe <thorpej@nas.nasa.gov>
Date: Sat, 15 Aug 1998 11:40:49 -0700
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On Sat, 15 Aug 1998 11:53:23 +0000 
 Mike Smith <mike@smith.net.au> wrote:

 > I'd be curious to know if anyone's measured the cost of the SCSI<->ATA
 > translation for ATA disks, since that's where performance is really an 
 > issue.  Nobody cares how efficient access to a Zip disk is, but an 
 > extra 10% overhead on ATA disk transactions would really hurt.

We're not doing it for ATA, but then again ATAPI disk aren't ATA.

We are, however, doing a SCSI-like layer for ATA.

 > Command passthrough doesn't (can't) work directly, as many fields are 
 > different sizes.  I think what you mean is that there's no need for any 
 > intelligence in the translation, which is fair enough.

...this doens't really matter if you're, e.g., passing mmc commands
to an ATAPI CD-ROM or CD-R.  They're the same for SCSI and ATAPI.

Jason R. Thorpe                                       thorpej@nas.nasa.gov
NASA Ames Research Center                            Home: +1 408 866 1912
NAS: M/S 258-5                                       Work: +1 650 604 0935
Moffett Field, CA 94035                             Pager: +1 650 940 5942

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