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

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Avg. Core
Core i5-661
Core i5-750
Core i7-870
Thermalright MUX-120 with stock fan @ 5.6V (900 RPM).
Ambient temperature: 22°C.

The average core temperature reported by SpeedFan stabilized at 41°C after 10~15 minutes on full CPU load, about 10°C lower than its quad core cousins. The Thermalright MUX-120 heatsink used during testing was cool to the touch even when the processor was stressed to the limit. Board temperatures were also excellent with the VRMs around the CPU socket staying below 45°C and the single chipset heatsink never passing 40°C at its hottest point, as measured by an IR thermometer.

Motherboard Impressions

Budget Intel boards typically have very restrictive controls in the BIOS and the DH55TC is no exception. The BIOS lacked controls for memory speed and did not allow any voltage modification. In addition, TurboBoost could not be customized; only an on/off toggle was provided.

As for compatibility, neither the Core i5-750 or i7-870 would POST in the DH55TC, even with the latest BIOS from Intel. The DH55TC claims support for i7, i5, and i3 on the box, so in theory it should work, if not now, then in the future. The i5-661 would not work in our older DP55KG LGA1156 motherboard either.


The Core i5-661 is more than just a dual core version of the Lynnfield core processor. A die-shrink from 45nm to 32nm gave Intel the space to fit both a dual core processor and their latest onboard graphics chip, GMA HD, onto the same package. This combination is very energy efficient, rivaling the power consumption of a low speed Core 2 Duo, despite the Core i5-661's much higher clock speed and overall performance.

GMA HD is a marked improvement over GMA X4500HD, rendering HD video using significantly fewer CPU cycles and delivering much better 3D performance. Regarding the latter, it should be noted that the GPU core of the i5-661 has a higher operating frequency than the version of GMA HD found on the rest of the Clarkdale lineup. Even with this advantage, it still trails behind AMD's HD 3300/4200 with Sideport memory. Still, with either CPU/chipset, if you play even 3~4 year old games at the typical native resolution of a modern widescreen LCD monitor, you will probably need a 'real' video card to get decent framerates and image quality.

The Core i5-661's <$200 price tag brings up the question of whether the equivalently priced quad core Core i5-750 is superior. If you're a heavy multi-tasker or often use demanding applications that can take advantage of four cores like some video encoders, professional image editing software, and games, then the i5-750 is the better candidate. However, if a program doesn't scale that well with multiple cores, the higher clock speed of the i5-661 can give the i5-750 a run for its money. For example, in our TMPGEnc video encoding test, the i5-661 finished only 5% slower than the i5-750.

If you're a more casual user but you still value snappy performance, a dual core like the i5-661 is an excellent choice, particularly if you have no need for discrete graphics. In many instances the higher clock speed is actually more useful. In addition, the i5-661 is very energy efficient and runs fairly cool, so you don't need an enormous, expensive heatsink/fan to make it a quiet computing experience. The 6x0 series should run even cooler as they utilize a slightly slower version of GMA HD; Intel lists their TDPs at 73W vs. 87W for the i5-661. In summary, the Core i5-661 is a significant landmark in Intel's long stream of processors.

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Articles of Related Interest
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Athlon II X4 630 & 620: Affordable Quad Cores
Intel's LGA1156 and Lynnfield core
Intel Q9550S: A Greener Quad Core?
AMD Phenom II X2 550 BE & Athlon II X2 250
AMD Phenom II X4 955 Black Edition for AM3

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