Intel Core i5-661: A 32nm CPU with Integrated Graphics

CPUs|Motherboards
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CPU/VRM Power Consumption

To get an idea of how much power the CPU actually requires, we measured the current (through a 0.01 ohm shunt resistor) and voltage at the ATX12V connector in various CPU load states. This allows us to calculate the power demanded by the CPU and the board's VRM (DC-DC converter).

DC Power Consumption
Test State
Core i5-661 @ 3.33GHz
(Stock)
Core i5-661 @ 2.26GHz (Underclocked)
System
CPU + VRM
Diff.
System
CPU + VRM
Diff.
Idle
18W
5.3W
12.7W
18W
5.2W
12.8W
CPU Load
60W
46.0W
14.0W
45W
32.4W
12.6W
CPU + GPU
Load
67W
51.2W
15.8W
54W
39.0W
15.0W
CPU Load (Turbo)
63W
48.0W
15.0W
N/A
CPU Load + GPU Load (Turbo)
69W
52.7W
16.3W
N/A
CPU + VRM power measured from the ATX12V connector (combined DC draw of VRMs and CPU).

By our measurements, our i5-661 sample used 5.3W when idle and up to 46.0W when stressing the CPU with Prime95, with an indeterminate amount lost to VRM inefficiency. The addition of FurMark's GPU stability test resulted in an additional 5.2W draw.

Between 13W and 16W was used by the rest of the system which consisted of the motherboard, two sticks of memory, a notebook hard drive, idle Blu-ray drive, keyboard and mouse.

System Power Consumption Comparison

To compare the Core i5-661 to other processors we've tested, we changed the hardware to match our CPU testing platform, swapping the notebook hard drive for a Velociraptor and using a GeForce 9400GT rather than integrated graphics.

Test Results: System Power Consumption (DC)
Processor
Idle
VC-1
Playback
CPU
Load
C2Q Q9550
47W
57W
115W
Core i5-750
37W
55W
107W
Core i5-661
(Turbo)
31W
45W
79W
Core i5-661
31W
45W
78W
C2D E7200
41W
50W
69W
X4 955 BE
56W
79W
171W
X3 720 BE
58W
77W
127W
X2 550 BE
48W
67W
106W

Back in September we reviewed the Core i5-750 and i7-860 Lynnfield quad core processors and found them to very energy efficient. The i5-661, utilizing a smaller manufacturing process and half the cores is even more thrifty when it comes to power draw. Power consumption was 10W less than the Core 2 Duo E7200 when idle and only 10W more on full CPU load. AMD's fastest dual core, the X2 550 Black Edition, an 80W chip, was off the mark by 20~30W.



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