AMD and Intel faced off in the dual core arena through 2005 and 2006, with the Athlon 64 X2 taking first blood, and literally carving the Pentium D from stem to stern, but Intel and their impressive Core 2 architecture certainly had the last laugh. Dual core has quickly transformed into the standard processor base for all levels of computing, from laptops to high-end x86 servers, and dual core PDAs are probably right around the corner. The next phase is to take multi-core to the next level, incorporate four processor cores into one platform, and enable quad-threaded performance. AMD has stated their 4x4 solution achieves this goal, but uses two dual core processors in concert, while the Intel response has been to literally slap two Core 2 processors onto one CPU package. This is a similar design strategy that Intel employed with the Pentium D 800 series, and the Core 2 Extreme QX6700 shares the advantage of an accelerated time to market.
In the truest sense, the 65nm Core 2 Extreme QX6700 takes the existing Core 2 architecture and doubles it. This processor includes two individual 2.66 GHz Core 2 dies incorporated on a single package, which is how Intel has been able to fast-track the release of Kentsfield core technology. This differs from a specialized multi-core design like the Core 2 or Athlon 64 X2, as there is no sharing of internal resources, and the two dies exist as separate entities. This also means that the processors cannot share data internally, instead communicating along the slower CPU bus, and sharing the same memory interface.
The design of the Core 2 Extreme QX6700 also means that many Core 2 features are not fully actualized on the Kentsfield core. For example, current Core 2 processors feature 2MB or 4MB of Advanced Smart Cache, which is shared between the two cores. This gives the Core 2 processor a great deal of flexibility, and it could theoretically allocate all 4MB of L2 cache to a single core in gaming scenarios, while dynamically shifting it between cores in a multi-threading environment. This type of flexibility is not present in the Kentsfield core, there is no facility for sharing of the 8MB of total L2 cache, and instead it acts like dual Core 2 processors, each sharing 4MB of L2 cache. This also affects the entire processor, with absolutely no shared resources between the dual processor dies, resulting in a larger, more power-hungry core with potential duplication.
Slapping two Core 2 processors on the same processor substrate is certainly not a bad thing, especially when you consider the advantages of the architecture. Sure, the entire L2 cache is not shared, but there is still a total of 8MB, with each Core 2 unit able to dynamically allocate its own 4MB based on workload. The Core 2's L2 bus is fully 256-bit, and L1 cache has also been increased to 32KB instruction/32KB data caches per core (from 16KB/16KB on the Pentium D), and each has 8-way associativity. The Core 2 includes support for Intel SpeedStep technology, and so too does the quad core Kentsfield. This is a huge advantage, as with four cores firing away, power management is a major concern. The Kentsfield also supports features like Execute Disable Bit, Intel 64 Technology, SSE4, and Intel Virtualization Technology, among others.
The Intel Kentsfield core is being introduced as a single processor release, the Core 2 Extreme QX6700. It supports the LGA775 socket, is clocked at 2.66 GHz, features 8MB (2x4MB) of combined L2 cache, and runs on the 1066 MHz front-side bus. The processor's max voltage is 1.35V and it sports a TDP (Thermal Design Power) of 130W, which is a significant increase from the 75W TDP of the 2.93 GHz Core 2 Extreme X6800. As with other Extreme processors, Intel has disabled "overspeed protection" and allows overclockers to play with the CPU multiplier. These quad core Kentsfield processors are also compatible with some existing LGA775 motherboards, allowing a level of upgradeability for end users.
The Core 2 Extreme QX6700 shares the same external design of any Core 2, and includes an integrated heat spreader and a standard LGA775 interface. Inside there may be dual Core 2 processors bolted on, but you couldn't tell from the outside. The Intel naming convention may seem strange initially, especially given that early rumors had it pegged with a Quad or Quadro brand name, but Intel has stuck to its Core 2 Extreme guns and simply added in a "Q" prefix to the model number. Even the rest of the model numbers stays consistent, as the 2.66 GHz Core 2 Extreme QX6700 shares the same clock speed as the Core 2 Duo E6700. In one way, it works, but in the other, it's very surprising that Intel is not promoting QUAD in big neon lights.