Power And Heat
To be honest, I didn’t tackle all of those benchmarks thinking that Intel’s Xeon E5620 was going to somehow magically outperform a six-core desktop chip. I also didn’t think 4 MB of additional L3 cache was going to put a huge lead over the 45 nm Bloomfield design, with its 8 MB repository.
Rather, I was hoping to see higher frequencies at lower operating temperatures, perhaps with a little power-savings sprinkled on top.
I took ambient temperature readings in between each result using an Extech TM200 thermometer. You can disregard those orange and red bars—the GPU remains fairly consistent at idle and load, regardless of the processor behind it. More interesting are the blue and green bars.
It comes as little surprise that the stock Xeon E5620 is an example of low thermal output thanks to conservative clocks and low operating voltage.
The overclocked Xeon runs significantly warmer due to a 1.6 GHz frequency increase and a higher fixed voltage.
Two additional cores mean that the Core i7-970 gets hotter still—about 10% warmer than the quad-core Xeon.
And an older manufacturing process translates to significantly hotter idle and load temperatures for the overclocked Core i7-930. And when you consider the ambient temp hovered around 32 degrees in my lab, adding 57 to that sticks the loaded Bloomfield core up around 90 degrees. That’s uncomfortably warm, long-term. In fact, I’d probably recommend dialing back to 3.73 GHz or so and dialing back voltage a bit in order to hopefully get a little more useful life out of the chip.
At idle, the overclocked Gulftown-based processors use the same amount of power. The stock Xeon is quite a bit more conservative with its consumption. And the Core i7-930 is only moderately higher than the other 4 GHz CPUs.
Load the CPUs down, though, and you get another story entirely. The stock Xeon E5620 is still fairly power-friendly. Overclocked and overvolted, consumption rises by nearly 100 W. Yet, the Xeon E5620 still uses 50 W less than the overclocked Core i7-970. And the Xeon uses roughly 60 W less than the other overclocked quad-core chip in this comparison, Intel’s Core i7-930.
Those results translate over to CPU+GPU power measurements, too. The overclocked Xeon E5620 uses 60 W less than the 4 GHz Core i7-930 setup. So, you’re getting roughly the same performance, significant power savings, and less heat output for a $100 price premium.