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AMD Phenom II X4 940 Black Edition
Today AMD released the latest addition to its CPU line-up, the aptly named Phenom II range. These quad core processors will eventually completely replace the existing Phenom series and, for the foreseeable future, be AMD's answer to Intel's new Core i7 processors.
For today's launch there will be only two processors available, the Phenom II 940 Black Edition and Phenom II 920. The former will run at 3.0GHz (a marked increase from the previous Phenom's best of 2.6GHz) and cost a relatively modest $275 while the latter runs at 2.8GHz and comes at an even more reasonable $235. Compare this to the prices of even the cheapest Core i7 and it doesn't take a genius to work out that these Phenoms, despite their improvements, won't be gunning for the top performance spot. Nonetheless, considering how little most of us utilise the power of even modest dual-core processors, there's still plenty of reason to consider AMD's latest.
The key difference between the first generation Phenoms and the Phenom IIs is the move from manufacturing the chips on a 65nm process to a 45nm process. This yields chips that consume less power and produce less heat than the equivalent designs on the older process, which means CPUs can either run at the same speed as before but consume less power or run faster for the same power usage.
Another result of the shrink is either an increase in the number of chips that can be produced per wafer of silicon (making them cheaper) or that the same number of chips can be produced with more logic crammed into the same space.
It's this latter route that AMD has taken with the Phenom II. The actual chip is almost identical in size to the existing Phenom but it incorporates around two thirds more transistors - up from ~450 million to ~758 million.
A large proportion of this extra silicon is taken up by an increased amount of on-die cache memory. Just like previous Phenoms, Phenom II uses three levels of cache with the first two levels remaining at 128KB (64KB for instructions, 64KB for data) and 512KB per core. However, the third L3 level has increased from 2MB all the way up to 6MB, which is shared by all four cores. AMD estimates this accounts for around a five per cent performance increase over previous Phenoms. Obviously this is something that's impossible for us to test directly so we'll have to take its word for it.
Besides the cache and clock frequency increases, there aren't too many fundamental changes to the core CPU design. That said, a number of tweaks have been made to both increase performance and reduce power usage.
For a start, AMD has improved Cool and Quiet (CnQ) - the technology that reduces clock speeds when parts of the processor are idle. The previous incarnation would dynamically clock each core independently, which in theory sounds great but because of the way Windows Vista handles the distribution of tasks across multi-core processors, it could result in reduced performance. But by going backwards and simplifying the CnQ to dynamically clock all four cores at once, the new Phenoms don't see a performance hit anymore. So it's now safe to have CnQ on all the time.