enabling DMA on hard drives

[Dave Stubbs]

Stewart C. Russell wrote:

> Dave Stubbs wrote:
>
>>
>> Best to let the kernel do what it does best.  Heck - even Windows 
>> seems to get THIS one right most of the time...
>
>
> Unless I explicitly issue a hdparm command to enable DMA on both my 
> desktop and laptop, DVDs are unwatchable. There seem to be no side 
> effects from doing this.


Likely your kernel does not have the CONFIG_IDEDMA_PCI_AUTO flag 
enabled, or you have a computer whose IDE chipset is not supported in 
the default kernel config.  I had to rebuild my kernel with extra IDE 
chipsets selected for a Dell Server (Serverworks chipset) and also for a 
clone I built with the DFI LanParty motherboard.  On both these systems 
the IDE performance was abysmally slow at the start but when I enabled 
support for the proper IDE chipset and flagged CONFIG_IDEDMA_PCI_AUTO 
they sped up vastly, and there were no reliability problems.  hdparm was 
no longer necessary because the kernel automatically enabled DMA during 
bootup.

Dave...
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