It seems Richard Hodges wrote:
On -current you can set the transfer mode to anything you like
(and that the controller/device supports) using atacontrol,
so no need to hack the kernel anymore :)
> I was just testing out a new configuration, when I get two of
> these about an hour apart, and then another today:
>
> ts8 /kernel: ad4: READ command timeout tag=0 serv=0 - resetting
> ts8 /kernel: ata2: resetting devices .. done
>
> Needless to say, this is a problem. Here is the boot info:
>
> ts8 /kernel: ad0: 29311MB <Maxtor 53073H6> [59554/16/63] at ata0-master UDMA66
> ts8 /kernel: ad3: 29311MB <Maxtor 53073H6> [59554/16/63] at ata1-slave UDMA66
> ts8 /kernel: ad4: 29311MB <Maxtor 53073H6> [59554/16/63] at ata2-master UDMA100
> ts8 /kernel: ad5: 29311MB <Maxtor 53073H6> [59554/16/63] at ata2-slave UDMA100
>
> The first two are on a VIA 82C686 bridge, the second two are HPT370.
> I am wondering if UDMA100 is just too much for the cabling, and am
> interested in finding out whether running them all at UDMA33 would
> provide an extra safety margin.
>
> I see in dev/ata/ata-dma.c, ata_dmainit() checks some cable flag, and
> reduces the UDMA capability to UDMA33 if neccessary. This seems like
> a decent place to hardwire it for testing. Is there any other place
> that also needs to be changed?
>
> If there actually is a difference in stability, would anyone favor
> a new sysctl to put an arbitrary cap on the UDMA capabilities? As
> far as I can tell, there should not be ANY performance difference
> between UDMA100 and UDMA66, or even with UDMA33 if there is only
> one drive per cable.
>
> Comments and suggestions are appreciated :-)
>
> -Richard
>
> -------------------------------------------
> Richard Hodges | Matriplex, inc.
> Product Manager | 769 Basque Way
> [EMAIL PROTECTED] | Carson City, NV 89706
> 775-886-6477 | www.matriplex.com
>
>
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-S�ren
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