[CentOS] DMA disabled on SATA disk with Core Duo/i955 machine (Inspiron 6400)

[James Pearson]

On 23/10/06, first last <prelude_2_murder at yahoo.co.uk> wrote:
> I am trying to use CentOS 4 on this machine and it does not allow me to
> set DMA to 1, it just says that it is not possible. I have tried
> updating to the latest release and it still won't work.
>
> I have searched for it on Google and there is a thread mentioning the
> same machine and CentOS, but none of the solutions (-p, -X 12) seem to
> work at all and there is no "it works!!!!!" message.
>
> Is there anyway I can get DMA working or will I have to wait for CentOS
> 5? Will any of the "unsupported" kernels work? (I would try Ubuntu's
> kernel on CentOS, as I am successfuly using that distribution, but it
> is a bit stupid not to use SELinux and it probably wouldn't work
> either).

I don't think you can use hdparm on SATA disks?

I know some BIOS's allow SATA disks to look like IDE 'legacy' drives
(/dev/hdX) - if this is the case, then the OS may be using the generic
IDE driver and it might not support DMA.

If this is what you are seeing, then you might want to turn off the
legacy or compatible mode in the BIOS and use the drives via /dev/sdX
...

James Pearson