Enabling DMA w/ Grub

[SporkNet]

How do I use DMA with a IDE channel in GRUB? In lilo I think it is 'Append "IDE1=DMA"'

[Choozo]

Read up on 'hdparm' instead (if you have that installed) man hdparm

Cheers :)

[fancypiper]

If you're talking about enabling dma for drives (hdparm), the best place to put that is in a startup script such as/etc/rc.d/rc.local in Redhat. If you need to pass any options to the kernel using grub, simply add them to the end of the kernel command.

Grub homepage (http://www.gnu.org/software/grub/grub.html)

Speeding up hard drives using hdparm (Speeding up Linux Using hdparm)

For UDMA 33/66/100 capable systems, add the -X option, and then this number i.e. (-X 69)

-X 33 ====> Multiword DMA
-X 66 ====> ATA-33 (UDMA2)
-X 68 ====> ATA-66 (UDMA4)
-X 69 ====> ATA-100 (UDMA 5)

I think there is some newer stuff than that is supported now.

[beat_feet]

Sorry but as a rookie I thought I should ask when editing rc.local to perform certain things at bootup do I type them in just like it was a command in the terminal? Or is there another way to go about this? Also when using hdparm is there a command to show what the current setting for dma is on the devices.
Thanks

[mdwatts]

hdparm /dev/hda will show the current settings.

SporkNet... You can use ide1=autotune or ide1=ata100 etc.

Search around the web and you should be able to find a list of available options you can use.

[drashkeev]

When Editing rc.local, just type the commands in, in order, without the prompt symbol.

As to enabling DMA, I believe it is done automatically on most modern distros, the kernel defaulting to the fastest performing mode. To see a list of available modes, go hdparm -i /dev/hda