Intel's new Unlocked 655K delivers some juicy overclocking, but otherwise sits in an awkward spot in the market...
We've had Intel's range of Core i5 and i3 processors for some time now. They were notable at launch for integrating a graphics adapter within the processor's package, seen as the larger of the two rectangles (dies) pictured. They also failed to really impress us for much the same reason.
Now, integrating a graphics card into a processor is something to be truly excited about - like what AMD's working on with their Fusion tech - but what we see in the i5 655K is nothing even close to a real card. Instead, it is a slightly improved version of the GMA chips we've seen in netbooks, and though we were told by Intel spokespeople that they were "great for gaming", in reality they're enough for high-definition video and Farmville. The 655K also boasts a lower-clocked version of the GMA HD, running at 733MHz rather than 900MHz, though it can be marginally changed via the BIOS.
Thankfully the processing cores aren't quite the pushovers that the graphical side is, and though there are only two, they are descended from the 980X architectural design and boast all the relevant improvements: 32nm, increased SSE instructions, and a lower power usage per core. Though they still have 64KB and 256KB of L1 and L2 cache dedicated to each processing core, there is a large shared pool of L3 cache to the tune of 4MB that should offer some breathing space when running intense workloads.
The 655K also integrates sixteen PCIe 2.0 lanes within the processor itself alongside a memory controller, eliminating the need for a dedicated northbridge and allowing direct access to expansion cards and system memory. There is enough bandwidth on offer for dual-card graphics, if one is willing to sacrifice potential performance, but it is really a mainstream platform so single-card is perhaps more appropriate. Annoyingly the inbuilt memory controller resides with the GMA die on the processor package, and though it offers high bandwidth and lower latencies to the graphical processor, the logical processors are inflicted with much higher penalties, as data must flow between dies - creating the same problems that were seen with the LGA775 platform.
Actual performance isn't too bad, performing well in most benchmarks due to the large amount of cache, though Everest suffers markedly from the aforementioned design flaw. Overclocking to OC1's frequency of 3.6GHz, boosted from a stock of 3.2GHz, was easier than breathing inwards, and did not even require a voltage increase from a stock of 1.2V for stability. OC2 was similarly easy, as the QPI bus and voltage were raised to 175x24 and 1.35V respectively, for a real-world speed of 4.2GHz. This speed was very noticeable within Windows, and there was a tangible difference in system responsiveness compared to stock speeds.
We continued overclocking the traditional way, increasing the QPI bus to a final stable speed of 185x24 at 1.375V for a stable 4.44GHz that scored 14,844 points in Cinebench R10 - representing a 39 per cent clockspeed increase, and a 36 per cent rise in performance to boot. This overclocking performance is identical to that of the Core i3 540, which is a strange coincidence.
The 655K is slightly different to the $50-cheaper i5 650, and the extra cash grants an unlocked multiplier at the cost of a stock heatsink, which is not included. Annoyingly the 655K topped out at a speed of 4.42GHz under 134x33 settings, and scored only 14033 in Cinebench. It's nice for those who want a mild overclock without affecting other components such as the motherboard or memory; but it doesn't offer any real value to overclockers. Instead, we'd point you towards a vanilla 650 - or even better, an i7 860.
Issue: 137 | June, 2012