Labs

To see the results table, click here.

To see the benchmarks, click here.

Most of the dual-core PCs submitted for testing in our labs have Intel Core 2 Duo processors. There's a massive range available, from the 1.8GHz E4300 right up to the 3.16GHz E8500, and we've tested most of them here.

Each core in a Core 2 Duo has its own 64KB L1 cache, which is smaller than those used by AMD's Athlon 64 X2 processors. The L2 cache varies in size, but is always shared by the two cores. This is more efficient when running multi-threaded applications, as data and instructions don't have to be duplicated across two caches.

The Core 2 Duo's architecture makes it more efficient per clock cycle than the Athlon 64 X2, and so it performs better at similar clock speeds. For example, the 2.2GHz Core 2 Duo E4500 is significantly quicker than the 2.2GHz Athlon 64 X2 4200+. If you're looking to compare Intel and AMD processors, then look at benchmark performance rather than clock speeds.

All Core 2 Duo processors use the LGA775 socket. If upgrading, check your motherboard's manual to see which processors it supports. Many older LGA775 motherboard chipsets don't support Core 2 Duo processors, and others need a BIOS update to be compatible.

Different ranges

The 4000 series includes the cheapest Core 2 Duo processors. They use the Allendale core and are manufactured using a 65nm process, making them reasonably power efficient and cool. They run at a 200MHz external bus speed, but as with all Intel processors this is quad-pumped, and is in effect 800MHz. This is the slowest frontside bus speed of all Intel's Core 2 Duo processors.

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All the 4000 processors have 2,048KB of shared L2 cache, which again is the smallest in this range.

The 6000 series includes some of the original Core 2 Duo processors, such as the E6700. All these processors are based on the Conroe core and use the same 65nm process as the 4000s. Most use a quad-pumped 333MHz (1,066MHz effective) external bus, although newer designs use a quicker 1,333MHz external bus. Check your motherboard's manual to see which external bus speeds it supports, and use the table below to find the right processor.

A faster external bus speed increases the bandwidth available to the processor when it's talking to other system components, such as memory and the PCI Express bus. Quicker speeds can increase performance, as shown by the E6550's better benchmark score over that of the E6600 in our Multitasking test, despite the E6600's slightly higher clock speed.

All the 6000-series processors have large 4,096KB L2 caches. The 6000 series includes the Core 2 Extreme X6800, which has an unlocked multiplier that lets you overclock easily and more stably by not having to adjust the external bus speed.

The new 8000 series includes the quickest dual-core processor available: the E8500. All 8000-series processors are manufactured using a 45nm process, making them more power efficient and cooler. They all have an external bus speed of 1,333MHz. A large 6,144KB L2 cache is shared between both cores, improving the processor's performance by reducing the number of times it has to access the system memory.

Specific processors

The Core 2 Duo range has a lot to offer, whether you're building a new PC or upgrading an old one. The Core 2 Duo E4500 and E4600 are good choices, but you can ignore the slower E4300 and E4400 processors, as the Pentium Dual Core E2180 and E2200 are better value.

The 6000 series is showing its age. Many of these processors look pricy next to the 4000 series, and the rest are outperformed by the 8000 series. If your motherboard won't support processors with a 1,333MHz external bus speed, though, the E6420 is your best option.

The 8000 series is very impressive. The E8400 costs only £19 more than the cheapest 6000-series processor, but produced one of the highest scores here for a dual-core processor. The E8500 is faster still, but doesn't justify its higher price when compared with the E8400.