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It is not my profession but I think my question isn't that stupid :)

Intel i7-2600 supports RAM: DDR3 1066/1333 non ECC

Same for Xeon, Amd A4 & A6 and so forth..

Why are there RAM chips with bus speed of 1600Mhz?

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  1. Before memory controllers were integrated into the CPU, they actually operated at higher clock speeds. The CPU integrated ones are still faster overall, due to not having a delay between memory controller and CPU, but for those discrete memory controllers (north bridge of chipset), you'd want the higher RAM. It's somewhat ironic that you've tagged your question fsb and then mentioned the Core-i line and AMD APUs, none of which have a Front Side Bus.

  2. The "supported" RAM speed of those CPUs is the officially supported speed. Overclocking is quite common.

  3. Even when the RAM chip is used at a lower frequency, the higher-spec RAM chips will have fewer wait states between e.g. address stable until first data word read back. The clock speed controls the burst throughput within a RAM block. There are many many other timing factors affecting system performance than burst throughput.

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Good point about the [fsb] tag. I didn't even see notice that. –  surfasb Jan 16 '12 at 0:16

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