|Notebook drives generally run at 5600/5200 RPM. These are not high performance drives. I doubt you will see any appreciable speed increase using ACHI.|
My advice is to not worry about it. If you are running less than 2GB of RAM, bumping that may help overall performance.
What do hope to accomplish by changing the setting?
BIOS is independent of the OS, so I don't think there is any hack that will allow you to change the setting without re-installing.