Today if you have USD 200 to spend on a CPU you have basically four options: Core 2 Duo E8400, Core 2 Quad Q6600, Phenom X3 8750 and Phenom X4 9550. In this review we will compare the performance of these four CPUs to answer a simple question: among these processors, which one is the fastest? We will also answer another common question: what is the best option, a CPU with more processing cores but with a lower clock rate or a CPU with less processing cores but with a higher clock rate? Get ready for this Intel vs. AMD duel.

But first let’s meet the contenders.

Core 2 Quad Q6600 is the simplest and most inexpensive quad-core CPU from Intel, running at 2.4 GHz – the same clock rate used by Phenom X3 8750. It features an 8 MB L2 memory cache divided into two 4 MB caches, one shared by cores 1 & 2 and another shared by cores 3 & 4. Each core has a 32 KB L1 data cache and a 32 KB L1 instruction cache. It runs externally at 266 MHz transferring four data chunks per clock cycle, giving a performance as if it were working at 1,066 MHz. It is based on the 65-nm “Core” CPU core and is also known by its codename, Kentsfield.

Core 2 Duo E8400 is a 45 nm CPU based on the new Penryn core, which brings the new SSE4.1 instruction set, not present on Q6600 and also not present on AMD CPU’s. It comes with a 3 GHz clock rate, works externally at 333 MHz (“1,333 MHz”), and has a single 6 MB L2 memory cache. It is also known by its codename, Wolfdale.

Phenom X3 8750 is a triple-core CPU and hence the “X3” on its name. It is based on the new K10 architecture from AMD and the main difference between CPUs from this architecture compared to CPU’s from Intel and previous AMD CPU’s is the use of an individual L2 memory cache on each CPU core plus a third cache shared by all cores. This processor runs at 2.4 GHz, the same clock rate as Core 2 Quad Q6600, so we were really curious to see a comparison between the two, even though X3 has one less core compared to Quad. This CPU is also known by its codename, Toliman, and is based on the B3 stepping die (stepping is the version of the silicon die used by the CPU; this is also called “revision”), which doesn’t  suffer from the infamous TLB bug that affected the first Phenom models. All Phenom models ending with “50” are based on this new die and thus don’t have this bug, while models ending with “00” may have this bug if they use a die before revision B3. Phenom CPU’s have a new instruction set called SSE4a, which is simply the addition of two new SSE instructions and despite its name it has nothing to do with SSE4.1, available on Core 2 Duo E8400 and that brings 47 new instructions.

Finally Phenom X4 9550, which is a quad-core CPU just like Core 2 Quad. It has one core more than Phenom X3 8750 but runs at a lower clock rate, 2.2 GHz, and that is how both can have the same price tag. In fact during this review we will be able to compare these two Phenom models to see what the best option is, to have one extra CPU core but a lower clock rate or a higher clock rate but one less core. Phenom X4 9550 is also known by the codename Agena. As you could assume from what we explained on previous paragraph, this CPU is based on the latest B3 stepping and doesn’t suffer from the TLB bug.

AMD CPU’s have the memory controller embedded inside the CPU and because of this architecture they have two external busses instead of just one like Intel CPU’s: one bus connects the CPU to the memory and another, called HyperTransport, connects the CPU to the chipset. Phenom CPU’s use a new version of HyperTransport, 3.0, and both Phenom CPU’s we reviewed are based on the lowest rate from HT3, 1,800 MHz (7,200 MB/s). Other AMD CPU’s like Athlon 64 use a 1,000 MHz (4,000 MB/s) HT bus.

In the table below you can find a comparison of the main specs from the CPUs we included in this review.

CPU Cores Internal Clock External Clock L1 Cache L2 Cache L3 Cache Technology TDP
Core 2 Duo E8400 2 3 GHz 1,333 MHz 64 KB x2 6 MB x1 45 nm 65 W
Core 2 Quad Q6600 4 2.4 GHz 1,066 MHz 64 KB x4 4 MB x2 65 nm 95 W
Phenom X3 8750 3 2.4 GHz * 128 KB x3 512 KB x3 2 MB 65 nm 95 W
Phenom X4 9550 4 2.2 GHz * 128 KB x3 512 KB x4 2 MB 65 nm 95 W

* 200 MHz base clock and 1,800 MHz (7,200 MB/s) HyperTransport link.

TDP stands for Thermal Design Power which advises the user of the maximum amount of heat the CPU can dissipate. The CPU cooler must be capable of dissipating at least this amount of heat.

AMD CPU’s are based on socket AM2+ while Intel CPU’s are based on socket LGA775.


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.