Clarkdale's Efficiency: Core i5-661 Versus Core 2, Athlon II, And Phenom II

Intel's Core i5-661 (Clarkdale) CPU

The Core i5-661 is a unique model from Intel with the family's fastest graphics clock. Its HD Graphics unit runs at 900 MHz, as opposed to the 733 MHz found on all other Core i3/i5 processors. Other than that, there are no differences between the models. All HD Graphics cores have 12 EUs (Execution Units) with Intel third-generation shaders. DirectX support is still limited to 10.0, but OpenGL support was upgraded from 2.0 to 2.1. Due to the 661’s higher graphics speed, the whole package's TDP is higher, as well, reaching up to 87W versus 73W on all other Core i3/i5 models.

Remember that the TDP applies to both to the processor and the graphics unit, which was formerly part of the chipset. Despite the slightly higher TDP, Intel says that the entire ecosystem of coolers and platforms for 65W processors can also be used for the 73W parts, which is significant in helping to keep platform costs lower. Base and Turbo Boost speeds for the Core i5-661 are identical to the Core i5-660 as well.

The new Core i3 and i5 dual-cores are not identical to the Core i5 and i7 quad-cores. Intel took a clue from VIA and added a new feature that we found to be extremely powerful: an AES engine. Clarkdale supports a set of six additional instructions designed to accelerate FDE (full disk encryption), file encryption, Internet security, and voice-over-IP applications. As you will see in the synthetic benchmarks, these modifications make a dramatic difference in PCMark Vantage’s encryption tests.