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To: Bruce Evans <bde@zeta.org.au>
cc: freebsd-hackers@freefall.cdrom.com, kuku@gilberto.physik.rwth-aachen.de
Subject: Re: Why IDE is bad 
In-reply-to: Your message of "Wed, 22 Mar 95 21:32:15 +1000."
             <199503221132.VAA11806@godzilla.zeta.org.au> 
From: David Greenman <davidg@Root.COM>
Reply-To: davidg@Root.COM
Date: Wed, 22 Mar 1995 03:39:29 -0800
Sender: hackers-owner@FreeBSD.org
Precedence: bulk

>>Regarding the difference in CPU utilization, could it be - I don't
>>know the driver internals - that it's the bounce buffer technique
>>that costs CPU while the SCSI controller uses bus master transfers all
>>the time? Or were you comparing VLB EIDE vs. SCSI ?
>
>This might explain why my Intr time is so much lower than Poul's.
>I have only 16MB, and don't use option BOUNCE_BUFFERS.  The bcopy()
>for bouncing is done in a call from biodone().  biodone() is called
>from the interrupt handler, at least for the wd driver.

   Bounce buffers are not used on wd-style drives.

-DG