Rimhill sets the maximum cd-rom speed to a specified level in your drive. This will prevent the annoying sound if a cd-rom is in your drive and also speed up access time if the drive is rarely used since the drive must only spin up to 8x instead of 48x.
Nero DiscSpeed, previously Nero DriveSpeed, is a disc speed measurement and performance diagnostics tool. It reads the speed of a CD-ROM drive. Not included in the Nero 11 or later, is part of Nero Free Tools.