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Date: Sun, 14 Dec 2008 23:16:48 +0100 (CET)
From: Wojciech Puchar <wojtek@wojtek.tensor.gdynia.pl>
To: "Jason C. Wells" <jcw@highperformance.net>
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Cc: freebsd general questions <freebsd-questions@freebsd.org>
Subject: Re: Disk Errors
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> ad2: FAILURE - READ_DMA timed out LBA=0
> ad2: TIMEOUT - READ_DMA retrying (1 retry left) LBA=1
> ad2: TIMEOUT - READ_DMA retrying (0 retries left) LBA=1
>
> The flash drive is detected with 3940272 sectors.  Is there a way to control 
> the LBA= parameter?  Does it matter if I try?
no.

>
> How can I control the number of retries?
>
> I read that FreeBSD doesn't use the BIOS at least for CHS.  Does FreeBSD use 
> the BIOS for PIO and UDMA modes?
no.

try disabling dma with

set hw.ata.ata_dma=0

bootloader command