How do determine the clock per instruction for my application (CACHE ON)?
The PPC 405 has a time stamp counter that you can read using XTime_GetTime() (xtime_l.h). This is incremented once for every clock cycle, so it provides an easy way to measure application timings. EDK ships with Power PC ISS where you can get an estimate of the number of instructions. Taken together, you can calculate number of clocks Per Instruction.
Your Clock Per Instruction will vary widely based on the application. If you are mostly running from caches, then you can get quite close to a Clock Per Instruction of 1.