Intel's LGA1156 and Lynnfield core

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TEST RESULTS

Our test systems consist of 2x2GB of DDR3 memory (1333 MHz, 9-9-9-24-1T timings), a GeForce 9400GT graphics card, WD VelociRaptor hard drive and an OEM Seasonic power supply. Turbo Boost was disabled during testing — we consider it overclocking. The ambient temperature was 21-22°C.

Test Results: General System Power Consumption (AC)
Test State
i7-965
i7-870
i5-750
QX9650
Q9550
X4 955
Idle
84W
54W
52W
68W
64W
73W
VC-1
Playback
100W
72W
72W
86W
75W
99W
CPU Load (half cores)
145W
104W
96W
122W
120W
157W
CPU Load (all cores)
203W
147W
130W
142W
140W
201W

The new Lynnfield processors impressed us immediately after general power consumption tests. Compared to LGA775, the LGA1156 configurations used about 10W less less power in idle and during VC-1 video playback, and approximately 20W less when two of the four cores were stressed with Prime95. With wattage numbers in the low 50's, they rival some dual core processors in idle power draw. The Core 2 Quads were already very energy efficient, and i7-870 and i5-750 proved to be even more frugal.

The power draw of the two Lynnfields were similar — nothing but negligible differences were noticed until the CPU was stressed heavily. With two cores working at their maximum, the 870 used about 8W more. The difference more than doubled to 17W when all four cores were taxed.

Undervolted Test Results: General System Power Consumption (AC)
Test State
i7-870
i7-870
i5-750
i5-750
QX9650
Q9550
Stock
UV
Stock
UV
Idle
54W
53W
52W
48W
68W
64W
VC-1
Playback
72W
69W
72W
67W
86W
75W
CPU Load (half cores)
104W
94W
96W
85W
122W
120W
CPU Load (all cores)
147W
128W
130W
110W
142W
140W
i7-870 undervolted to 1.025V stable (~1.1375V stock).
i5-750 undervolted to 1.0625V stable (~1.1625V stock).

Undervolting yielded further gains in energy efficiency. We managed to get the 870 semi-stable (10 minutes of Prime95) at stock speed with 1.025V in the BIOS. The 750 required 1.0625V. This resulted in slightly less power draw in idle and during VC-1 playback, saved 10W when two cores were stressed with Prime95, and 20W with all four cores under load.


CPU screenshot: i7-870 undervolted to 1.025V. CPU-Z reported 0.768V when idle (1.2 GHz).

CPU screenshot: i57-750 undervolted to 1.025V. CPU-Z reported 0.704V when idle (1.2 GHz).



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