Copyright by William Lloyd Bircher 2010 - The Laboratory for ...

The difference between C0-Idle and C0-Max is determined by the amount of power spent
in switching transistors, which would otherwise be clock-gated, combined with worst-
case switching due to data dependencies. C0-Max can be thought of as a pathological
workload in which all functional units on all cores are 100 percent utilized and the
datapath constantly switches between 0 and 1. All active phases of real workloads exist
somewhere between these two curves. High-IPC compute-bound workloads are closer to
C0-Max while low-IPC memory-bound workloads are near C0-Idle.
3.4.5 Power Management-Aware Model
The model improves on existing on-line models [Be00] [BiJo06-1] [IsMa03] by
accounting for power management and temperature effects. Like existing models it
contains a workload dependent portion that is dominated by the number of instructions
completed per second. In this case the number of fetched operations per second is used
in lieu of instructions completed. The fetched µops metric is preferred as it also accounts
for speculative execution. In addition to fetched µops, a retired floating point µops
metric is also included. This accounts for the power difference between integer and
floating point ops in the AMD processor. Unlike the Pentium 4 processor which exhibits
little difference in power consumption between integer and floating point applications,
the AMD processor exhibits much higher power consumption for high-throughput
floating point applications. A further distinction of this model is that it contains a
temperature dependent portion. Using workloads with constant utilization, processor
temperature and voltage are varied to observe the impact on static leakage power.
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