OTOH, the Atom is not that much slower than a C2D when you are not doing SSE operations. It's exactly the opposite. Not counting multiplies, pshufb, and a few

OTOH, the Atom is not that much slower than a C2D when you are not doing SSE operations. It's exactly the opposite. Not counting multiplies, pshufb, and a few other instructions, SSE operations are mostly reasonably performant. The real problems are that the Atom has: 1) no out of order execution, which results in an enormous performance penalty on all code. 2) very high penalties for many "transfers" between operations: for example, the result of an arithmetic op cannot be used for addressing for quite a few clocks. This penalty is humongous when dealing with pointers-to-pointers in managed code, lookup tables, and so forth. 3) a completely un-pipelined multiplication unit that takes 7 cycles, compared to the pipelined 3-cycle Core 2 unit. 4) an enormous number of instructions that were microcoded internally (and thus extraordinarily slow) in order to reduce TDP and chip size. 5) only two integer ALUs, which can only dual-issue in some specific cases. Overall, a 1.6Ghz Atom is significantly slower than a 1.6Ghz Pentium 4. A Core 2 is at least twice as fast per clock per core as a Pentium 4. And a Core i7 is another 40-50% faster per clock per core... If you want something that gets out significantly more performance per watt than a Core 2 or Core i7, look at the ARM Cortex A9.