The Q8400 operates at 2.66GHz with a 333MHz front side bus speed. It is manufactured using Intel's 45nm process technology and has a 95W thermal design power (TDP). The CPU can operate using core ratios from 6 to 8 and has 4MB of L2 cache.
Intel's Q8400 fills the $180 price point in Intel's line up that competes directly with AMD's Phenom II X4 940 BE processor. But the Q8400 has a tough fight on its hands as the X4 940 BE runs at 3GHz and offers an unlocked multiplier.
CPU-Z reveals the processor's details and settings. Note the 4MB (2MB x 2) L2 cache shown above. This is the only difference between this processor and the more expensive 2.66GHz Q9400, which has 6MB of L2 cache. We will show you the performance difference between the two chips later on in this review.
We love free upgrades. One of the best ways to get more performance from your PC is to overclock the processor. From a stock frequency of 2.66GHz, we overclocked the Q8400 to an impressive 3.92GHz using a TRUE 120 and 1.36V. We started with a 333MHz FSB and raised it slowly while testing for stability along the way. It wasn't until we passed 490MHz FSB that we ran into any issues so we backed it back down and settled for the 3.92GHz overclock. We would like to note that we stayed within Intel's recommended operating voltage (0.85V - 1.3625V) to achieve this overclock. With higher voltages and more powerful cooling, even higher frequencies are likely possible.