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Date:      Sun, 30 Jul 1995 08:27:01 -0700
From:      "Justin T. Gibbs" <gibbs@freefall.cdrom.com>
To:        joerg_wunsch@uriah.heep.sax.de (Joerg Wunsch)
Cc:        terry@cs.weber.edu (Terry Lambert), freebsd-current@freebsd.org, babb@freebsd.org
Subject:   Re: Update on my aic driver problems 
Message-ID:  <199507301527.IAA12070@freefall.cdrom.com>
In-Reply-To: Your message of "Sun, 30 Jul 95 11:34:34 %2B0200." <199507300934.LAA23968@uriah.heep.sax.de> 

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>As Terry Lambert wrote:
>> 
>> > The aic chip is actually an AIC 6260, and the `aic' driver isn't very
>> > clear about this, but it looks like it would only support AIC 6360's. :-(
>> 
>> The 6260 doesn't support scatter/gather, I believe.
>> 
>> > Does anybody know what's the difference, and if it would be allot of
>> > work to hack it?  By now, all i get is ``sd0(aic0:0:0) timed out''
>> > when sysinstall tries to find the drive(s), even though the driver has
>> > been properly probing the chip and announced the disk drive.
>> 
>> I don't know how you'd hack it onto a chip that doesn't support it.
>> 
>> 8-).
>
>Hmm, well.  Scatter/gather is a required feature for FreeBSD, ain't
>it?  Hmm, pity.  Perhaps i could find an IDE disk for it plus a spare
>old IDE adaptor.

No, its not.  What you'll have to do is allocate a 64k contiguous 
staging buffer and do the transaction from there.  Since scatter/gather
is handled at the controller driver layer, the rest of the SCSI system
makes no assumptions about it use... it just happens that most transactions
are to buffers that are not physically contiguous, so if you use DMA,
you must have the staging buffer.  It should be possible to get it to
work, but the performance won't be that great.

>
>-- 
>cheers, J"org
>
>joerg_wunsch@uriah.heep.sax.de -- http://www.sax.de/~joerg/
>Never trust an operating system you don't have sources for. ;-)

--
Justin T. Gibbs
===========================================
  Software Developer - Walnut Creek CDROM
  FreeBSD: Turning PCs into workstations
===========================================



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