Intel has introduced several different revisions of the Core 2 architecture, but through higher clocks, larger L2 caches and die shrinks, these remained bolted to the LGA775 socket. Although newer CPU support was never a guarantee, it was still very surprising to see Intel sticking with LGA775, as the company historically changed platforms with the seasons. But nothing lasts forever, and the upcoming Core i7 processor release will pave the way for the next generation of processors, and this time, change the CPU package for a very good reason.
Although Intel has released many processors over the years, most of these offered only small iterations on existing designs, and were more evolutionary than revolutionary. In fact, the Core i7 is a bit different in that regard, and it represents a significant architectural shift away from the standard Intel CPU, and into a new world of multi-core computing. The 45nm Core i7 die size is 263 mm2 and transistor count is 731M, but that's only the tip of the iceberg and there have been myriad architectural changes.
For starters, the Core i7 is a true quad-core processor, and incorporates multiple cores on a single processor die, rather than the existing Core 2 quads, which feature two distinct processor dies on a single package. This matches the AMD Phenom, and the Core i7 will be Intel's first desktop processor with a native quad core design. Each of the four cores includes 256K of dedicated L2 cache (1MB per CPU) while sharing 8MB of L3 cache.
The Core i7 die also features an integrated memory controller, again matching AMD's existing design, and linking the processor directly to the system memory, without the need for a Northbridge chipset. The Intel Core i7 supports only DDR3 memory and does so in a very interesting way. It incorporates a triple-channel memory link, requiring matched triplets for the highest performance, and unprecedented memory bandwidth.
There is a caveat here, as the memory voltage is linked to the CPU, and Intel recommends no higher than 1.6V DDR3 memory or it may damage the processor. This effectively cuts off the Core i7 from most enthusiast-level DDR3 modules, forcing users to stick with more mainstream memory, while waiting for vendors to release Core i7-safe triple-channel DDR3 low-latency kits. The Core i7 will also introduce a brand new Intel LGA1366 socket, which will replace the venerable LGA775, and offer no backwards compatibility.
Another interesting change has been the deletion of the conventional Intel front-side bus, which has been replaced by the QuickPath interface on the Core i7 platform. QuickPath supplies a processor interconnect that is similar to AMD's HyperTransport. It offers 4.8 to 6.4 GT/s of bandwidth, using a bi-directional link, for up to 32.0 GB/s of overall bandwidth. So far, only the Intel X58 platform has been announced with support for QuickPath, and partners like NVIDIA may not even offer an alternative.
Another feature that has found its way back to the Core i7 is the thought-to-be-dead Hyper-Threading technology. This was introduced back in the single-core days as a way for a physical core to emulate multiple logical cores, thereby providing increased multi-threading performance and better multi-tasking. It worked, but it wasn't that long before both AMD and Intel started producing their own dual core processors, supposedly rendering the technology obsolete.
It made a small comeback with the Pentium Extreme Edition 840, before being properly exhumed for the Intel Atom. Now, Intel has turned Hyper-Threading loose on something far more powerful, and it allows the four cores of the Core i7 to emulate eight. Intel believes, and with good reason, that only a robust architecture like the Core i7 can fully maximize the resource sharing and multi-threaded performance offered by Hyper-Threading.
As an added bonus, the Core i7 will feature a Turbo Mode that will allow the individual cores to clock higher, while disabling the unused cores, should the system notice that CPU usage is low. For example, if only two cores are active, the platform can increase the multiplier on those two cores, leading to higher application performance while maintaining power and TDP ratings. The Turbo Mode will be most useful with games, especially as the single core setting will provide the highest potential overclock, up to a multiplier increase of 2.
Intel will be releasing three new Core i7 processors in November, and these will include a high-end Extreme Edition and a low-cost mainstream model. The Core i7-965 Extreme Edition covers off the high-end, and its 3.2 GHz clock speed matches the fastest Core 2 Extreme QX9770. The 2.93 GHz Core i7-940 is the performance option, while the 2.66 GHz Core i7-920 provides a mainstream entry point for interested buyers. All three Core i7 processors will have a TDP of 130W.
The clock speed is the obvious difference between the three Core i7 processors, but it goes a bit deeper. Naturally, the Core i7-965 Extreme Edition will have "overspeed protection removed" (an unlocked multiplier), but the QuickPath Interface speed will also differ. The Core i7-965 XE will have a full speed 6.4 GT/s link, while the Core i7-940 and -920 feature a lower 4.8 GT/s interface speed.
Supported DDR3 speeds also change depending on the model. The baseline Core i7-940 and -920 can only use DDR3-1066 in a triple-channel configuration, but the Extreme Editions will get rid of that limitation. The Core i7-965 XE offers standard DDR3-1066 support, but extends that into faster memory speeds, like DDR3-1333, -1600 and higher.