|R0||5 (Reason code)|
|R0||Corresponding MHz value|
The purpose of this call is to convert a speed index to a MHz clock rate.
Due to hardware restrictions or for performance reasons, most systems will only support a limited number of CPU clock rates. This call, along with Portable_Speed2 4 and Portable_Speed2 6 allow the user to enumerate the list of available clock rates. Index 0 is always the slowest available speed, and (return value of Portable_Speed2 4)-1 is always the highest available speed.