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Date: Tue,  5 Aug 2008 14:16:55 -0400
From: Sape Mullender <sape@plan9.bell-labs.com>
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Subject: Re: [9fans] Bizarre freeze
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I wonder why there is a command to turn on DMA on disks.  Could
it be that some disks don't work with DMA on?

	Sape

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Date: Wed, 6 Aug 2008 02:01:17 +0800
From: sqweek <sqweek@gmail.com>
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Subject: [9fans] Bizarre freeze
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 Ran into an interesting one setting up my cpu server. The following
reliably freezes the box:

# echo dma on >/dev/sdC0/ctl
# 9fat:

 Leaves the console totally unresponsive, no ^T^Tp, no ^P. rc -x on
9fat: gives "rfork e" as the final command.
 sdC0 is a cdrom. I can turn dma on for my sata disks (sdE0/sdF0) no problem.
-sqweek
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