ConclusionsWithout a doubt, Nehalem is what the server world has been waiting for – wiping away the last vestiges of the front-side bus and catapulting Intel’s system architecture into the modern era. Alongside substantial architectural improvements such as simultaneous multithreading, a redesigned cache hierarchy and others the impact on performance is profound. Our tests have shown performance benefits ranging from 30% up to 270%, which is even more remarkable considering that the core count was kept constant and frequency is roughly in the same ballpark (+/-15%), even with turbo mode.When looking at Nehalem compared to previous products, the performance gains are substantial, but the benefits in terms of power efficiency are just as striking. That is partially due to the improved system architecture – by distributing the memory controller amongst both CPUs in the system, FB-DIMMs become unnecessary because there are more aggregate pins available for physical layer interfaces. But the improvements in power control due to the power gates are quite significant as well – idle power dropped in half. Perhaps more importantly because it speaks directly to the power consumption of the CPUs, the power range for the Nehalem system was 105-395W, twice the Harpertown operating range that is between 294-450W. This makes Nehalem significantly more attractive than prior generations from a power stand point alone, ignoring the performance aspect. Together, the two advantages are quite compelling.This puts AMD in a bit of an uncomfortable situation. Prior to the launch of Nehalem, it might have been fair to characterize AMD’s position as slightly lagging in most cases, at parity in others, with a few strong points. Clearly, Nehalem will pull ahead of Shanghai by a fair margin in terms of performance for almost any workload. That leaves AMD’s 6-core Istanbul to compete with Nehalem, which seems like it should be a roughly even match as Istanbul offers both some interesting architectural tricks such as a snoop filter and also an increase in core count. However, the power efficiency issue remains tilted in Intel’s favor for now.
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