Dual-Core Versus Quad-Core: Part 2

AMD Phenom X4 9350e (2.0 GHz Quad Core)

AMD’s Phenom X4 processor has been around for almost a year, though it took AMD a few months to fix some issues with the first product generation. The current products are all fine and can be recommended, as AMD is delivering great bang for the buck despite the fact that Core 2 Quad processors are typically faster. The Phenom X4 9950 quad core, which runs at 2.6 GHz, costs only $220 and offers great performance for multi-threaded applications, while the 2.2 GHz Phenom X4 9550 can be found for less than $160. A Core 2 Quad processor typically costs at least 50% more, but the performance gains are nowhere near that level.

Phenom X4 9350e is a 65-W Part

We were more interested in a low power version of the Phenom X4 quad core, because AMD has had versions that fit into the 65 W power envelope, and because that allows a direct comparison with Intel’s Core 2 Duo processors, which are also rated at 65 W. Considering that the Phenom processors are manufactured using the 65 nm process, and that there is no Intel Core 2 Quad processor that would be specified at less than 95 W—Extreme Editions are rated at 130 W or 136 W—this is an interesting product.

However, we need to point out that a processor’s TDP only represents the maximum thermal output specified by the manufacturer. It doesn’t mean that a particular model has to reach this power level, and there are many CPUs that do not even come close to their maximum thermal design points. In addition, a processor specified at 65 W TDP does not have to be more efficient than, say a 95 W part, when it runs under a low or medium load, because TDP does not specify idle power. All the TDP says is that the 65 W quad core Phenom X4 9350e provides 2.0 GHz of four-core performance, while not exceeding its 65 W limit.

Aside from its low-power specification, the 9350e isn’t different from the other Phenom models. All have 64+64 KB instruction and data cache, as well as 512 KB of second level cache per processing core. In addition to that, AMD implemented a 2 MB third level cache as well, which is shared by all of the processing cores. Avoid the Phenom X4 models 9500 and 9600, as these are based on the B2 stepping that is known for issues with the so-called translation lookaside buffer (TLB). The B3 stepping Phenom processors are free of major bugs, and they all carry model numbers ending with -50, such as the 9350e. All regular Phenom X4 processors are specified at 95 W, 125 W or 140 W TDP, while the e9100 and 9350e stick to the 65 W envelope.

All Socket AM2+ processors come with an integrated memory controller for DDR2 memory. Phenoms support memory clocks of up to 667 MHz, resulting in DDR2-1066 speeds based on double data rate technology. New 45 nm processors based on Socket AM3 with 6 MB L3 cache will support DDR3 memory, but will probably not be available before 2009.

Phenom X4 Dominates Multi-Threaded Benchmarks

As expected, the multi-core advantage is only on paper for the majority of benchmarks, giving the Core 2 Duo at its fast 3.16 GHz an advantage in many software titles that simply seem to perform best at a good balance between two cores and high clock speed. Thread-optimized titles such as AVG antivirus, Fritz 11 chess, the Mainconcept H-264 encoder and WinRAR 3.8 run faster on the 2.0 GHz Phenom X4 than they do on the 3.16 GHz Core 2 Duo. Many other titles, though, provide better performance on the Core 2 solution despite their optimization for multiple cores.

AMD Loses The Efficiency Battle

AMD loses both power consumption disciplines to Intel, which doesn’t come as a surprise: four cores simply require more power than two. This is very much like comparing a big V8 engine and a small 2-liter 4-cylinder, so we don’t want to complain about it. As the synthetic benchmarks prove, the Phenom X4 does provide the better performance, but it is not efficient in most of the application scenarios, including our performance per watt testing using SYSmark 2007 Preview and a 3D game cycle using Crysis.