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Difference between the CPU_CYLES and PMCCNTR_EL0


I know that the Arm architecture supports the CPU_CYCLES (event # 0x0011) and an independent dedicated Cycle counter (PMCCNTR_EL0).  I assume that the PMCCNTR_EL0 and a PMU event counter that counts the CPU_CYCLES PMU event count the same thing -- which is the CPU cycles. Why does Arm architecture support two means for the same thing? 

Do people ever need to use a CPU_CYCLES given that a dedicated cycle counter already exist?