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Date:      Mon, 11 May 1998 23:10:14 -0700 (PDT)
From:      Tom <tom@uniserve.com>
To:        Tim Tsai <tim@futuresouth.com>
Cc:        am@f1.ru, Allen Smith <easmith@beatrice.rutgers.edu>, bofh@terranova.net, greg@uswest.net, freebsd-stable@FreeBSD.ORG
Subject:   Re: SCSI problems?
Message-ID:  <Pine.BSF.3.96.980511230137.9588C-100000@shell.uniserve.ca>
In-Reply-To: <19980512002903.24456@futuresouth.com>

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On Tue, 12 May 1998, Tim Tsai wrote:

> > > > the AHC_ options in the kernel configuration file.
> > > 
> > > Aren't those for EISA, not PCI devices in the first place? That's what
> > > the comments in LINT seem to indicate. I've also got an 2940UW,
> > > without any AHC_ options, and it hasn't been causing any problems -
> > > then again, the machine hasn't been up and running very long.

  No, the AHC_ options are can be used for either, but some EISA adapters
can't do scb paging.

> > Hm..  Powered off it will cause even less problems. Without tagging it's
> > too slow for UW and good HD..
> 
>   For some of us reliability is far more important than speed.  I bet
> you mount your filesystem async too huh?

  If it is too slow to do its task, that is even worse than unreliable.

  Also, an ncr adapter will do tagged commands quite well, and will
_easily_ outperform the ahc driver with tagged commands off.  It is also
much less expensive.  So basically, if you must run the ahc driver without
tagged commands, you could have saved money and gotten better performance
by getting an NCR810 or NCR875 based adapter.  However, the ahc driver 
with functioning tagged commands and paging is pretty quick, and handles
lots of simultaneous io better than an ncr based card.

  Or you could use a DPT card.  The card handles tags, so the driver
doesn't even need to know.  Since alot of SCSI processing is offloaded, it
is fast too.

> > Btw, I see no more of that disturbing messages when I added AUTO_EOI1
> > and BOUNCE_BUFFERS which I lost during upgrade..
> 
>   Hmmm, can somebody tell me why BOUNCE_BUFFERS is applicable here? These
> are PCI devices.
> 
>   Tim

Tom


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