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This paper describes the design and validation of a performance and power simulator that is part of the Mambo simulation environment for PowerPC[R] systems. One of the most notable features of the simulator, designated as Tempo, is the incorporation of an event-driven power model. Tempo satisfies an important need for fast and accurate performance and power simulation tools at the system level. The power and performance predictions from the simulated model of a PowerPC 405GP (or simply 405GP) were validated against a 405GP-based evaluation board instrumented for power measurements using 42 application/dataset combinations from the EEMBC benchmark suite. The average performance and energy-prediction errors were 0.6% and -4.1%, respectively. In addition to describing Tempo, we show examples of how well it can predict the runtime power consumption of a 405GP microprocessor during application execution.

Abstract:  Relatively good quality isotropy is observed in the central region of a turbulent boundary layer developing over a mesh screen rough wall. Spectra of velocity and, more especially, vorticity fluctuations satisfy isotropy over a significant wavenumber range. Inertial range scaling exponents ζ u2 (p) and ζ u3 (p) of moments of order p(?8) of increments of the transverse velocity fluctuations u 2 and u 3 are significantly smaller than the exponents ζ u1 (p) of increments of the longitudinal velocity fluctuation u 1. Exponents inferred from the locally averaged values of squared transverse vorticity fluctuations are only slightly smaller than ζ u1 (p). The difference between ζ u1 (p) and ζ u2 (p) [or ζ u3 (p)] more likely reflects the departure from isotropy of inertial range scales. There is evidence to suggest that the difference decreases with an increase in the Reynolds number and/or a decrease in the magnitude of the mean shear.

Measurements of the spanwise and wall-normal components of vorticity and their constituent velocity derivative fluctuations have been made in a turbulent boundary layer over a mesh-screen rough wall using a four-hot-wire vorticity probe. The measured spectra and variances of vorticity and velocity derivatives have been corrected for the effect of spatial resolution. The high-wavenumber behaviour of the spectra conforms closely with isotropy. Over most of the outer layer, the normalized magnitudes of the velocity derivative variances differ significantly from those over a smooth wall layer. The differences are such that the variances are much more nearly isotropic over the rough wall than on the smooth wall. This behaviour is consistent with earlier observations that the large-scale structure in this rough wall layer is more isotropic than that in a smooth wall layer. Isotropy-based approximations for the mean energy dissipation rate and mean enstrophy are consequently more reliable in this rough wall layer than in a smooth wall layer. In the outer layer, the vorticity variances are slightly larger than those over a smooth wall; reflecting structural differences between the two flows.

The measured anisotropy invariants of the Reynolds stress tensor in a self-preserving rough wall turbulent boundary layer indicate that the anisotropy is significantly smaller than in a smooth wall layer.