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Date:      Wed, 11 Apr 2001 14:11:41 -0700 (MST)
From:      "brian j. peterson" <rbw@myplace.org>
To:        freebsd-questions@FreeBSD.org
Subject:   turning off DMA pre-boot
Message-ID:  <Pine.BSF.4.21.0104111225540.26386-100000@malkavian.org>

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background:

i have a 4.3-BETA system that is freezing on me every few days.  (the
cvsup from 4.2-R to stable was done around March 11th.)  i have trimmed
down the kernel as much as possible in an attempt to isolate the problem,
but this hasn't helped so far.  the motherboard this system is on uses a
VIA chipset, and i have been hearing that VIA's DMA support is less than
perfect.  turning off DMA in the BIOS didn't seem to stop FreeBSD from
using DMA (at least according to 'sysctl hw.atamodes').  i was able to
turn off DMA _after_ boot by running 'sysctl -w hw.atamodes=pio,pio,'.  (i
just did this last night, so i'm not sure if this has solved the system's
freezing problem.)

question:

is there some way to disable DMA support (and force PIO mode) before the
system boots?  perhaps a kernel option or a loader option?

any help would be greatly appreciated.

thanks for your time,
brian

-- 
--===-----=======-----------=============-----------------===================
|    rbw aka bjp        |        god's final message to his creation:       |
|    rbw@myplace.org    |        we apologize for the inconvenience.        |
===================-----------------=============-----------=======-----===--


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