Using the New PPC4xx Indexed DCR Access InstructionsThe IBM PPC440H6, PPC464, PPC464FP, and PPC460-S embedded CPU cores implement several new instructions for accessing Device Control Registers (DCRs). These instructions provide indexed DCR accesses where the address of the DCR is taken from the contents of a specified register rather than being hard coded in the instruction. This permits DCR numbers to be computed at run time rather than requiring them to be known when the code is written. In addition, a pair of user mode indexed DCR instructions allow non-privileged code to access DCRs that are designated as user mode accessible.
