Message-ID: <3F01F1F5.5050907@pobox.com>
Date: Tue, 01 Jul 2003 16:41:25 -0400
From: Jeff Garzik <jgarzik@pobox.com>
Organization: none
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To: Jurgen Kramer <gtm.kramer@inter.nl.net>
CC: linux-kernel@vger.kernel.org
Subject: Re: ICH5 SATA causes high interrupt/system load?
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Jurgen Kramer wrote:
> Hi,
> 
> After reading about problems with ICH5 SATA (Intel 875P) I've
> set my BIOS back to normal mode for the SATA controller. So now the SATA
> drive appears as hdc instead of hde.
> 
> The SATA drive was working in both situations (enhanced/normal) the only
> difference is that with normal mode there no high system load caused by
> the SATA controller (As I reported in a previous mail).
> 
> What's causing the high interrupt count in 'enhanced' mode?


Well, in legacy mode (a.k.a. normal), each ATA port (a.k.a. channel 
a.k.a. bus) gets their own interrupt, which is never shared with another 
device.

In native mode (a.k.a. enhanced), two ATA ports share a single PCI 
interrupt.  Further, this interrupt may be shared with any number of 
other PCI devices.

So, high interrupt count is necessarily a worry because you're probably 
seeing a coalescing of multiple interrupt counts into one big one.

	Jeff


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