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From: Soeren Schmidt <sos@spider.deepcore.dk>
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In-Reply-To: <20030408153259.2a4b03ac.Alexander@Leidinger.net>
To: Alexander Leidinger <Alexander@Leidinger.net>
Date: Tue, 8 Apr 2003 15:56:07 +0200 (CEST)
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Subject: Re: cvs commit: src/sys/dev/ata ata-all.c
	ata-all.hata-chipset.cata-dma.c ata-pci.c ata-pci.h
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It seems Alexander Leidinger wrote:
> > > Yes... so what's the problem with ATA & TQ?
> > 
> > Its borked at the moment.
> 
> I know... let's assume it would work: what's the problem with ATA & TQ
> which prevents it from being as effective as the SCSI TQ?

None that I know of except maybe the number of tags (32)..

> > > > Besides, enabling ATA tags automatically enables the write cache.
> > > 
> > > This can be changed...
> > 
> > No it cannot, requirement of the HW.
> 
> Does this mean we can't use ATA-TQ in situations where we would use TQ
> without WC on a SCSI system (read: does it affect softupdates)?

Well, this has newer been found out by hard evidence. The only vendor
doing tags capable ATA disks doesn't want to tell, so we cant really
know for sure. However tests here indicates that the "WC effect" is
not in action when tags are enabled, but I could just have been 
unusually lucky...

-Søren