The Intel Core i7-2640M is the fastest dual core processor at the time of introduction in Q3 2011 and successor of the slower clocked i7-2620M. It is based on the Sandy Bridge architecture and offers Hyperthreading to handle 4 threads at once (for a better usage of the pipeline). Compared to the slower Core i5, the i7 offers a larger last level cache of 4MB. The base clock speed is 2.8 GHz but due to Turbo Boost it can reach 3.3 GHz (2 cores active) and 3.5 GHz (1 core active).
Sandy Bridge is the evolutionary successor of the Arrandale architecture. The most noteable improvements are the new 256Bit AVX instructions, the improved Turbo 2.0 and the integration of the graphics card into the 32nm CPU core.
Der i7-2640M offers an integrated graphics card ( Intel HD Graphics 3000) which is clearly faster then the older Intel HD Graphics in the Arrandale CPUs. As the new GPU is included in the CPU, it is also manufactured in 32nm and shares the fast level 3 cache with the CPU cores (using a new ring bus). In the 2620M it is clocked from 650-1300MHz (Turbo Boost), and in the 2640M it should be similar.
Furthermore, an improved dual-channel DDR3 memory controller is included on the CPU die that is used by the CPU and GPU part.
Due to the improved architecture and the new Turbo Boost 2.0, the average performance of the Core i7-2640M is higher than a similar clocked Arrandale Core i7 dual core. The performance should even excel the old high-end quad core models like the Core i7-820QM.
The 35W TDP rating includes the integrated GPU and memory controller.