Core 2 Quad Q9400

Core 2 Quad Q9400 is actually the first alternative to the well-known Core 2 Quad Q9300 with higher clock frequency. Its predecessors worked with 7.5x multiplier that combined with 333MHz system bus provided 2.5GHz frequency. Core 2 Quad Q9400 uses 8x multiplier, so its nominal frequency equals 2.66GHz.

Other features of both processors are the same. And it means that Core 2 Quad Q9400 is a typical Yorkfield processor based on two dual-core 45nm dies placed into a single processor package. However, just like Q9300, the new model has the same peculiarity that distinguishes it from the top quad-core solutions: smaller L2 cache. Instead of 6MB per core, Core 2 Quad Q9400 has 6MB L2 cache total. In other words, each of the two dual-core dies has L2 cache of half the size: 3MB.

Diagnostic utilities detect this peculiarity easily. Take, for instance, CPU-Z:

Note that this CPU has new R0 processor stepping that is currently used only in Q9400 or Q8200, i.e. the recently launched quad-core Intel solutions. It means that these processors are based on smaller semiconductor dies that are not the production scrapping but have 3MB L2 cache from the very beginning. In other words, Q9400 has almost the same dies as the latest dual-core Core 2 Duo E7400 processors.

R0 stepping belongs to the latest die modifications that we have seen only in the top dual- or quad-core processors so far. The interesting thing about it, is that it supports C3E and C4E power modes, just like E0 processor stepping, that allow saving more power in idle state.

So, if we disregard smaller cache-memory than that of senior processor models, Q9400 seems to be a pretty fully-fledged CPU. It supports the fastest 1333MHz processor bus and the complete set of technologies, including virtualization technology and the accompanying Trusted Execution Technology. However, this is why this processor belongs to the top Q9000 series.