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How much faster will Nehalem macs be?

here's some specs on Performance and power improvements

It has been reported that Nehalem will have a focus on performance, which accounts for the increased core size.[10] Compared to Penryn, Nehalem will have:
1.1x to 1.25x the single-threaded performance or 1.2x to 2x the multithreaded performance at the same power level
30% lower power usage for the same performance
According to a preview from AnandTech "expect a 20 - 30% overall advantage over Penryn with only a 10% increase in power usage. It looks like Intel is on track to delivering just that in Q4."[11]
Compared to a 3.0 GHz Core-based "Clovertown" microprocessor, the Nehalem-EP "Gainestown" processor will have 1.6x the SPECint_rate2006 integer performance and 2.4x the SPECfp_rate_2006 floating-point performance.[10]
Bloomfield systems will have a theoretical memory bandwidth of up to 38.4 GB/s using triple-channel 1600 MHz DDR3.[12] In experiments with a pre-release 2.93 GHz Bloomfield, AnandTech measured 12.0 GB/s copy bandwidth using triple-channel 1066 MHz DDR3, against 6.9 GB/s using dual-channel 1066 MHz DDR3 on a 3.0 GHz Core 2 Quad system.[13]
Overclocking Nehalem processors will only be possible with the X58 chipset. The mainstream PCH will not be capable of overclocking unless a hardware mod is found.[14][15]
 
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