Nehalem Performance Preview

April 7, 2009 by

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Valve VRAD

Our second content creation benchmark is a radiosity utility provided by Valve. VRAD is one of the three major phases in compiling a level with the Hammer editor for Valve’s Source engine. The first stage called binary space partitioning divides the level up into a set of polygons that can be represented as a tree-like structure. The second stage calculates visibility information for polygons and light sources. VRAD is the last stage, where radiosity is calculated for the level based on the number and positions of various light sources. It is also the most taxing of the three stages in compiling a level – hence the most useful benchmark from the perspective of a game developer.
Figure 4 – VRAD Performance
Figure 4 above shows the execution time for the radiosity calculations – so smaller is better in this case, and Nehalem leads by a substantial 30%.
Figure 5 – VRAD Power Consumption
The power profile for VRAD is quite interesting, as it shows two distinct phases. The initial plateau at 400 and 325 respectively for Harpertown and Nehalem, and then the power falls off for several seconds before spiking back up. Unfortunately, we are not familiar enough with the application to understand exactly what is occurring during this latter peak.
Figure 6 – VRAD Energy Efficiency
Unlike POV-Ray, VRAD does not naturally report throughput numbers (e.g. pixels per second) and instead relies on execution time to measure performance. Thus instead of dividing throughput by average power, we instead count the total energy consumption (in joules or watt-seconds), as shown above. Again, lower is better and Nehalem comes in roughly 40% lower than the prior generation.

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