Today we are going to see the performance of two new CPUs from AMD, Athlon II X4 635 (2.9 GHz) and Phenom II X2 555 (3.2 GHz), and compare it to other models from AMD and competitors from Intel.

On AMD product line, "X2" means that the CPU has two processing cores ("dual-core"), "X3" means the CPU has three processing cores ("triple-core") and "X4" means that the CPU has four processing cores ("quad-core").

The main difference between Athlon II and Phenom II is the presence of an L3 memory cache on Phenom II, making this CPU to provide a higher performance when compared to an Athlon II of same clock rate and same amount of processing cores. Both Athlon II and Phenom II are socket AM3 CPUs, meaning that they can be installed on socket AM2+ or socket AM3 motherboards, depending on whether you want DDR2 or DDR3 memories on your computer, respectively.

The new Phenom II X2 555 (3.2 GHz) comes with an attractive USD 99 price tag for a CPU on this clock range. In fact it comes with the exact same price tag as Athlon II X4 620 (2.6 GHz), a CPU that we’ve already reviewed and proved to provide a good cost/benefit ratio. So we are going to compare these two CPUs to answer the big question: since the two CPUs cost the same, which one is the best? The CPU with the higher clock rate and an L3 memory cache but only two cores or the CPU without an L3 cache and lower clock rate, but with four processing cores?

As a competitor to these two CPUs, we elected Pentium E6300, which is offered at USD 80. Since motherboards targeted to Intel systems are more expensive and since the difference in price between the motherboards we used on our review is exactly USD 20, we ended up with systems with the exact same price tag.

We see all the time other websites publishing flawed reviews, for instance comparing CPUs that are in completely different price range (e.g., comparing these CPUs from AMD with Core i3 or Core i5 models). Even when you compare CPUs on the same price range the comparison is flawed, because you have to put the cost of the motherboard into the equation, since you have to compare the price of the whole system, not only the price of the CPU alone.

The second AMD CPU we are reviewing is Athlon II X4 635 (2.9 GHz), which is being offered at a higher price point (USD 126). Intel doesn’t have an "exact" competitor to this CPU, so we decided to pick as competitor Core 2 Duo E7500 (2.93 GHz), which costs around USD 116 and was the closest match. This comparison should be really interesting because both CPUs run at almost the same clock rate, with the AMD unit having as advantage having four processing cores, while the Intel counterpart has as advantage having SSE4 instructions.

AMD is targeting these CPUs to be paired with motherboards with integrated video based on AMD785G. Because of that we had to pick a motherboard with integrated graphics on the Intel side as well (Intel G45). Of course several users will install the CPUs we selected on system without integrated graphics. So in order to cover this situation, we conducted two tests with each CPU: with on-board graphics and with a GeForce 9600 GT installed.

Before going to our results, let’s compare the main specs from the CPUs included in this review.


Gabriel Torres is a Brazilian best-selling ICT expert, with 24 books published. He started his online career in 1996, when he launched Clube do Hardware, which is one of the oldest and largest websites about technology in Brazil. He created Hardware Secrets in 1999 to expand his knowledge outside his home country.