Basically your drive is set to run a test and find out if your using 4x or whatever type of media your using. Then it only allows for up to that speed.
I personally am using a hacked firmware that disables that test and lets me burn anything at 8x speed. Only thing is, the media actually has to be able to handle it.
I know that Ritek 4x discs can handle 8x burning so I save loads of $$ by just using them. If I want to use the old Ritek 2x media, I have to manually set the speed back down to 2x, because the test is disabled.
Otherwise it will try to burn the 2x discs at 8x as well and that hardly ever works.
Tyler!