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Depends on what you mean by speeds, but there's a huge confluence of reasons that processors are where they are today. If you mean the clock speed specifically, then it's largely due to the inability to manufacture smaller gate widths in silicon. The Core 2 architecture by Intel, for example, uses a 45 nanometer gate width for transistors in each core. Core 2 was part of the Penryn family. The latest family is Nehalem, and it, too, uses 45 nanometer gate widths. Core i5 and i7 belong to this family, among others. Since the gate widths didn't shrink from the Penryn family to the Nehalem family, the power consumption of a single state change in a given transistor didn't decrease. Since the heat dissipation (and, therefore, power consumption) is proportional to both the gate width and the clock speed, this new architecture couldn't change the state of the transistors any faster than the previous one. Therefore, core clock speeds remained pretty constant. Getting to 45 nm was really tough. Going to the next frontier, which will likely be 32 nm, will be even tougher. So tough, in fact, that STMicroelectronics, Freescale Semiconductor, NXP Semiconductor and Texas Instruments have all decided to stop their process research. An article in 2007 claimed that Intel, IBM and Matsushita, AMD and Renesas would be the only organizations still pursuing R&D in this area. That's a vastly reduced set of brains and dollars on the gate width problem. If your question about "speed" is more general, well, then there's another discussion around multi-core architectures that's also fascinating. The primary technical advances in Nehalem versus predecessor families are its multithreading, caching, bus and memory management schemes. If you keep each core at 3 GHz, how can you efficiently use two 3 GHz cores to get, say, 1.5 times the speed of a single core? How can you efficiently use four 3 GHz cores to get, say, 1.5 times the speed of two cores? in this respect, processor speeds have increased significantly in the last 5 years, and will continue to do so as software is written to take advantage of these new architectures. But, then again, when was the last time you really found yourself waiting for your processor? It was probably your disk, your network or your brain that was the bottleneck in the first place. :-) |