Intel's Core 2 Duo processors

Does L2 cache size make much of a difference?

One topic that has been going around our forums for some time now is the discussion between the cache size on the lower-end Core 2 Duo processors. Both the Core 2 Duo E6400 and Core 2 Duo E6300 come with a 2MB L2 cache and are based on the Allendale core, while the three higher-end 4MB L2 cache Core 2 Duos are based on the now-famous Conroe core.

The SMT components on the bottom are laid out in exactly the same way. Despite the different cores - according to CPU-Z - on the higher and lower end Core 2 Duo chips, you will be pushed to notice the difference between the two without removing the heat spreader. It is unclear whether Allendale is actually a completely different die, or whether it is just a Conroe core with 2MB of the L2 cache disabled.

Despite Intel not shipping similarly-clocked Conroe and Allendale cores, we felt that the impact of L2 cache size warranted some further investigation. We ran our suite of benchmarks on a Core 2 Duo E6400 clocked at 2.13GHz, and then ran the same benchmarks on a Core 2 Extreme X6800 with an 8.0x multiplier forced. This meant that we would have a set of comparable numbers at 2.13GHz to determine the performance differences (if any) between chips equipped with 2MB and 4MB L2 caches. For more details on the system setup, please see our Test Setup page.

The amount of L2 cache does appear to make a difference - virtually across the board - but the difference isn't as big as some were making it out to be. In the application benchmarks, we found that there was a difference of around 2-3% on average. Both the large and small file compression and encryption tests really benefited from the additional cache, yielding performance improvements of between 6-9%.

In our two multitasking tests, we found that the 4MB L2 cache-equipped Core 2 Duo was around 2.5% faster, depending on the background task running. With MP3 encoding running in the background, we fond that the 4MB L2 cache Core 2 Duo was nearly 4% faster than it's 2MB L2 equipped sibling.

At low resolution, we saw varied improvements. Call Of Duty 2 yielded virtually no performance improvements at either 1024x768 or 1600x1200 with high details, while both Quake 4 and Half-Life 2: Episode One displayed larger performance improvements at 1024x768. However, when resolution was increased, only Half-Life 2: Episode One showed any kind of performance advantage on the Core 2 Duo with 4MB of L2 cache.

Overall, the Core 2 Duo with 4MB of L2 cache is quicker than the 2MB Core 2 Duos at the same clock speed, but there are several instances where there is little-to-no difference in performance.