Core 2 is the new desktop CPU family from Intel, based on the new Core microarchitecture. For desktops Core 2 comes in two flavors: Core 2 Duo, which replaces Pentium D, and Core 2 Extreme, which replaces Pentium Extreme Edition. Core 2 desktop version was formerly known as Conroe and in this review we will check the performance of two models, Core 2 Duo E6700, which runs at 2.66 GHz, and Core 2 Extreme X6800, which runs at 2.93 GHz. We will compare them to the most high-end CPUs from AMD to date, including Athlon 64 X2 5000+ and Athlon 64 FX-62. Who has the fastest desktop CPU, Intel or AMD? Read on.

Attention: This review has some innacurate results, please read our most recent review for more accurate results.

Pay attention to not confuse Core 2 Duo with Core Duo. Core Duo is the commercial name for a Pentium M manufactured using 65 nm process, codenamed Yonah, while Core 2 Duo is the commercial name for the CPU codenamed Merom (for laptops) or Conroe (for desktops), which uses the new Intel Core microarchitecture.

You can check the CPUs Intel sent us on Figures 1 and 2. Since they were engineering samples, they didn’t have their final markings on them. Instead they had an “Intel Confidential” marking. On Figure 2 you can see their bottom side. They use the standard socket 775 used by current Pentium 4 and Pentium D CPUs, the only difference you can see is the number and location of the capacitors found in the middle. We added our Pentium 4 550 (3.4 GHz) on the photo so you can see this.

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Figure 1: Core 2 Extreme X6800 and Core 2 Duo E6700 engineering samples.

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Figure 2: Core 2 Extreme X6800, Core 2 Duo E6700 and Pentium 4 550 (3.4 GHz).

Keep using socket 775 was a great move from Intel. Socket 775 motherboards launched before Core 2 CPUs were available may be compatible with them. There are two requirements: first, the motherboard must be capable of supplying the voltage required by the new CPU; and second, the motherboard must be capable of supplying the external clock rate (FSB) required by the new CPU. Unfortunately only newer motherboards are capable of supplying the voltage required by Core 2 CPUs.

Internally, however, Core 2 CPUs have nothing to do with Pentium 4 or Pentium D. While Pentium 4 and Pentium D are based on Intel’s 7th generation microarchitecture – also known as NetBurst – Core 2 is based on a new architecture, called Core, which is based on Pentium M’s (which is based on Pentium III’s - as you will see on next page, Core 2 CPUs report their Family ID as being "6", the same one as Pentium Pro, Pentium II and Pentium III). Please read our Inside Intel Core Microarchitecture tutorial to learn everything you need to know about this new architecture.

Since they use a totally different internal architecture, you cannot compare clock rates used by Core 2 CPUs with the ones used by other CPUs like Pentium 4 or Pentium D. Core 2 CPUs may be faster using a lower clock rate as they internally process things differently. In fact, we will check this aspect on our review. Here is a problem for the Average Joe. Even though Intel started identifying their CPUs by model numbers a while ago, people still tend to compare CPUs by their clock rates. It will be hard for us to say to which previous Intel CPU or to which AMD CPU each Core 2 model is comparable by just looking to their specs.

Let’s now take a closer look on Core 2 technical specs.