How to set burning speed?

(I use VC6.0, NeroSDK.)
I do know that it’s possible to set the burning speed in the NeroBurn function. However, if the speed has been set is larger than the max supported speed of the burning device, what will the speed burning actually be?
Any response will be appreciated.

See the following thread http://club.cdfreaks.com/showthread.php?t=94871