There are very few hexa-core processors in the wild. Intel has one, in the form of its expensive enthusiast ‘Gulftown' Core i7-980X Extreme Edition. AMD uses two hexa-core dies in its latest generation of Opteron server processors, and has become the first manufacturer to produce mainstream hexa-core CPUs in the form of the Phenom II X6 processors.
These Phenom II X6 CPUs are the latest iteration of AMD's now venerable K10 architecture that first appeared on the desktop with the launch of Phenom in late 2007. The Phenom II X6 CPUs are based upon the design codenamed ‘Thuban'; they resemble the recently released ‘Instanbul' Opteron processor, which slaps two hexa-core dies onto a single package.
Built using 45nm technology, these cores each have 128KB of L1 and 512KB of L2 cache. They all share access to 6MB of L3 cache.
The Phenom II X6 is designed to work with DDR3 1600 and supports faster speeds for some combinations of memory, thanks to AMD's Black memory profiles. AMD has so far released two mainstream Phenom X6 processors at competitive prices that will appeal to desktop system builders, and plans to launch more in the coming months.
As with the Dragon before it, AMD provides further scope and tools for overclocking if the CPU is used as part of a Platform that combines them with new AMD 890 chipsets and the ATI Radeon HD 5000 series graphics cards.
The top of the range Phenom II X6 1090T has six cores running at 3.2GHz - the T at the end of the name stands for Turbo-Core, an update of AMD Overdrive. Turbo-Core attempts to make the most of the processor for single-threaded applications and occasions where all six cores would be overkill.
AMD uses software to turn off three cores, and overclock the remaining three: in the case of the 1090T to 3.6GHz. This is similar to Intel's Turbo-boost technology but not as elegant. Whereas Intel can adjust how much how much the cores are overclocked in increments, AMD simply turns up three cores to a single higher speed when it detects that fewer than three are being used.
Turbo core is incredibly important to the Phenom II X6's performance. Because the majority of work performed by the processor in your average desktop is single threaded, the CPU will likely spend most of its time as an effective tri-core processor running at 3.6GHz. This isn't necessarily a bad thing; the processor offers the flexibility of adapting to its load in a crude but effective way.
AMD's literature about the Phenom II X6 suggests it is designed for ‘extreme megatasking' situations. Maybe a little hyperbolic, but it does indicate where the Phenom shines, which is when all six cores are working away.
It was noticeable in our testing that single threaded and light multitasking tests show performance improvements in line with those expected from a faster version of the K10 core. In our real world benchmarks the Phenom II X6 1090T scored 1.74 overall, which is in line with similarly clocked Phenom II processors tested in the past.
However when we used Maxxon's Cinebench to load up all six cores with rendering tasks there was a huge improvement over quad core Phenom II processors. In our tests the X6 scored 1.07 points in the single core rendering test and 5.65 points in the multicore one.
That six cores perform more than five times better than one core is impressive, especially when you consider that the single core was running at 3.6GHz, thanks to Turbo-Core, while the multi-core tests had six cores each running at 3.2GHz.
While you can pair the X6 with 890FX, 890GX and 870 chipsets, the 890FX is the one AMD suggests for partnering the Phenom II X6. It offers some nice additional features, such as native support for SATA 6Gbps, support for two 16x PCI Express lanes (or four lanes running at 8x) to allow for multiple graphics cards, and improved PCI-Express connectivity for other onboard devices.
But, chipset decisions aside, the major advantage for the Phenom II X6 is that it offers six cores for the price of four Intel cores. Intel's processors still beat AMD's in single-core performance, but if your workload involves rendering or other tasks that can take advantage of the number of threads rather than raw speed, the Phenom II X6 stands out.
We'll have to wait until AMD lifts the lid on its Fusion platform next year to see the next generation of the AMD vs Intel war. What AMD has done with the Phenom II X6, however, is play to the architecture's strengths.
It is a capable CPU, has more cores than its competitors and is relatively cheap. When paired with the 890FX chipset it brings technologies like SATA 6GB/s that do not yet appear on Intel's chipsets, and the motherboards available for the platform are similarly cheap.