The Athlon 64 X2 has been around for almost two years, but the most interesting models are exclusively available for Socket AM2, which hosts processors with support for DDR2-800 memory. While the regular dual core portfolio starts with a 3800+ at 2.0 GHz, we recommend going for a model with some more performance. This makes a lot of sense, as the most expensive Athlon 64 X2 processor, the 6000+, only costs $241. The 2.5 GHz 4800+ model (this one is a 65 nm version) carries a $136 price tag. However, we decided to use the 5600+, as it runs at 2.8 GHz, but still is available for less than $200.

It is important to mention that AMD does have a product to challenge Intel's Core 2 Quad and Core 2 Extreme QX6700 and QX6800, but you will have to purchase a very special platform for it. The Athlon 64 FX-70 processor family largely utilizes AMD's entry-level Opteron platform, which is based on Socket 1207. AMD simply turned it into a top-end consumer product and branded the platform 4x4. Purchasing FX-70, FX-72 or FX-74 means purchasing a processor kit that includes two CPUs - the FX-70 starts at 2.6 GHz, while the FX-74 is the 3.0 GHz top model. Unlike workstation or server class Opteron systems, the 4x4 runs on unbuffered DDR2-800 memory.

AMD has made clear that the next-generation 65 nm quad-core, known as Barcelona and to be publicly called Phenom, will work in existing AM2 solutions. It remains unclear how the 4x4 platform will be supported. Since Intel also announced a dual-socket platform, we're sure that AMD will be ready with a processor product for 4x4.

Athlon 64 X2 5600+

It's difficult to understand AMD's model strategy, as the firm does have working 65 nm technology, which we found to be very energy-efficient. However, it might not be suitable for high clock speeds yet, as AMD only uses it for the mainstream processors (4000+ to 4800+) as well as an energy-efficient version (EE) called the 3600+.

There are two 5000+ models, one using the 90 nm process, the other one based on 65 nm manufacturing, but every processor rated 5200+ and up is a 90 nm part. The reason why we put emphasis on this is the power consumption and heat dissipation: the 90 nm CPUs are rated at a maximum thermal design point of 89 W, while the 65 nm CPUs have a 65 W limit. Thus, getting the more advanced technology generally is favorable, though not always.

The 5600+ looks particularly interesting to us, as it offers a 2.8 GHz clock speed, making it 200 MHz faster than the 5200+. Typically we wouldn't say this is important, as the clock speed difference is a mere 8% increase, but the speed bump comes at a premium of only $10.

We also included the 3.0 GHz 6000+ model in our benchmarks, because the results clearly show that 200 MHz more clock speed does not necessarily pay off. Have a look at the memory clock speed considerations on the next page.