Intel Lynnfield Core i5-750 & Core i7-870 Processor Review

by MAC     |     September 6, 2009

Power Consumption / Temperature Testing

Power Consumption

Although improved performance is obviously a cornerstone of this new mainstream platform, Intel have also promised substantially better power efficiency than what we have previously seen with Core 2 chips. Can they deliver as promised? That's what we are here to find out.

For this section, every energy saving feature was enabled in the respective BIOSes and the Windows Vista power plan was changed from High Performance to Balanced.

For our idle test, we let the system idle for 15 minutes and measured the peak wattage through our UPM EM100 power meter. Here are the results:

We are very, very impressed with what Intel have accomplished here. These Lynnfield processors have a 40-45% lower idle power consumption than either of our Core 2 Quad models. The i5-750 uses a remarkable 56% less power at idle than the i7-920. Clearly, Lynnfield's Power Control Unit (PCU) is much more aggressive in downclocking, undervolting, and simply disabling unused cores than any other mainstream or high-end processor.

For our CPU load test, we ran Prime 95 In-place large FFTs on all available threads for 15 minutes, measuring the peak wattage via the UPM EM100 power meter. Here are the results:

Here we have a tale of two processors. The i5-750 doesn't have the power-hungry Hyper-Threading feature, so it has a very impressive full load result. Compared to the i7-920, we are seeing a remarkable 42% reduction in full load power consumption. While the i7-870 is a noticeable 12% more power hungry than the i5 model, it is still about equal to current Core 2 Quad models, while offering vastly better performance. Clearly, Lynnfield's performance-per-watt is unprecedented, and this is saying a lot since the Bloomfield processors had set the new benchmark in that regard when they were first released.

For our overall system load test, we ran Prime 95 In-place large FFTs on all available threads for 15 minutes, while simultaneously loading the GPU with OCCT v3.1.0 GPU:OCCT stress test at 1680x1050@60Hz in fullscreen mode.

All you folders out there should love these results! The Lynnfield/P55 platform has up to 23% lower full system load power consumption than Bloomfield/X58, that's almost 90W from the wall when comparing the i5-750 and i7-920. Clearly, the removal of the X58 IOH, which itself was a 24W part, and the integration of the PCIe controller into the processor, combined with other energy-saving features, have resulted in a very tangible drop in overall power consumption. This is definitely the greenest high performance platform out there right now.

Temperature Testing

For the temperature testing, we had both the stock Intel Core i7 CPU cooler and a Thermalright MUX-120 at our disposal. The system was left to idle for 15 minutes, and then we ran Prime 95 In-place large FFTs for 15 minutes. The ambient temperature was 23°C/73.4°F.

i5-750: Stock Intel cooler on the left, MUX-120 on the right

i7-870: Stock Intel cooler on the left, MUX-120 on the right

Needless to say, the horrendously dinky little stock cooler that Intel have bundled with the Core i5-750 and Core i5-860/870 is mediocre at best and insulting at worst. The Thermalright MUX-120 on the other hand is a pretty damn good cooler, which is obviously not surprising since it is based on the proven Ultra-120 Extreme design. It is hard to give an objective opinion regarding whether Lynnfield runs cooler than current Core i7's since we don't yet have the ability to test an identical cooler on both platforms. Having said that, we can say that the i5-750 runs a fair bit cooler than the i7-870, and this is because it lacks the heat-spewing Hyper-Threading feature.

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