svn commit: r183981 - head/sys/dev/ata/chipsets

[Scott Long]

On Fri, 17 Oct 2008, John Baldwin wrote:
> Author: jhb
> Date: Fri Oct 17 16:03:37 2008
> New Revision: 183981
> URL: http://svn.freebsd.org/changeset/base/183981
>
> Log:
>  - For chipsets that can't do 64k transfers, fall back to 32k transfers
>    (still a power of 2) rather than 63k transfers.  Even with 63k transfers
>    some machines (such as Dell SC1435's) were experiencing chronic data
>    corruption.

It should be noted that breaking a 64K transfer into two 32K transfers is 
much more ideal than breaking it into a 63k transfer plus a 1k runt. 
Modern drive firmware actually sees the disk internally as 4k sectors now 
instead of 512 byte, so avoiding runt transfers and non-power-of-2 
transfers helps quite a bit with performance.

>  - Use the MIO method to talk to the Serverworks HT1000_S1 SATA controller
>    like all the other SATA controllers rather than the compat PATA
>    method.  This lets the controller see all 4 SATA ports and also
>    matches the behavior of the Linux driver.

Thanks for working on these two issues.

Scott