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Intel Lynnfield Core i7-870 and ASUS P7P55D - Overclocking, power consumption and temperatures

As you may have gathered from our benchmarks we also included an overclocked Core i7-870, running at 4.0GHz. This was a very quick test to see if we could easily do over 4.0GHz and due to time constraints we settled for 4.0GHz. The overclocking was done with a Noctua NH-U12P cooler and the voltage was increased from 1.160V to 1.35V, and the multiplier was set to x20 with 200MHz BCLK frequency.

We have no screenshots to share of the actual overclocking, but we can assure you that there were no problems in getting the processor stable at this speed, and we tested it plenty. We hope to present more thorough tests with Lynnfield seriously overclocked to make it bit more fun.

Power consumption

An interesting detail with Lynnfield is that the processors are rated to operate within the 95W TDP envelope, unlike 130W for big brother Core i7-9xx with the Bloomfield core. Intel has, despite the increased number of transistors managed to lower power consumption radically with the new Lynnfield core, the question is how this actually pans out in real life. Using a simple energy meter in the outlet we measured the power consumption of the entire system, without monitor, both when idle and fully loaded (wPrime loading all possible threads).

Power Consumption
Idle [W]
i7-870 (4.0GHz)
i7-965 (3.2GHz)
Phenom II 965 (3.4GHz)
i7-870 (2.93GHz)
  0 80 160 240 320 400

Power Consumption
wPrime [W]
i7-870 OC (4.0GHz)
i7-965 (3.2GHz)
Phenom II 965 (3.4GHz)
i7-870 (2.93GHz)
  0 80 160 240 320 400

The results are clear. Intel's new Lynnfield core is a lot more efficient than the older Bloomfield model, and we see that Intel's TDP specifications are justified as the system consumes about 40W less than Core i7-965 both when idle and under load. Phenom II X4 965 operating at 3.4GHz is quite hungry too and consumes more power than Intel's Core i7-870 CPU, even though it ends up behind in many benchmarks.

The processor costs half as much though so it will take some time for you to save up the price difference if we just consider the lower power consumption of Lynnfield.


We also decided to make some quick temperature readings of the Intel processors. We used two more or less identical coolers (Noctua NH-U12 and NH-U12P), which should render similar results. Still, you should consider the numbers below with a pinch of salt since we haven't made any more scientific tests and there is a slight difference between the coolers.

We measured the temperatures at idle and load (30min Arena chess stress test) with both Intel's LGA1156 reference cooler and Noctua's NH-U12P cooler. At the same time we compared temperatures of Intel's Core i7-965 processor, equipped with a Noctua NH-U12P cooler. The ambient temperature was 23°C.

Temperature Idle
Noctua NH-U12P S1156 (i7-870)
Intel Stock HSF (i7-870)
Noctua NH-U12 SE1366 (i7-965)
  0 20 40 60 80 100

Temperature Load
Noctua NH-U12P S1156 (i7-870)
Noctua NH-U12P SE1366 (i7-965)
Intel Stock HSF (i7-870)
  0 20 40 60 80 100

Temperatures show the same trend as the power consumption tests. Lynnfield is a lot more efficient and even if the clock frequency is lower with Core i7-870 there is a great difference in temperature. We see that Intel's slim reference cooler is hardly a product for overclockers since it already at stock speed can close in on temperatures around 80°C.

Lynnfield isn't just fast, it's also energy efficient and cool.

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