I can only lament the fact that Intel isn’t selling the Xeon E5620 on the desktop as a different K-series SKU with an unlocked multiplier. I’d even take a $10 or $20 premium on a part like that. Nevertheless, with a bit of fancy footwork, it’s possible to overclock this thing to 4 GHz and beyond.
Is Intel’s Xeon E5620 a solid enough value to displace CPUs like the Core i7-930 and -950 in the minds of ambitious overclockers? Not definitively, no. It’s on par. But because its multiplier is set so low, you really need 1) a good motherboard and 2) a solid approach to overcoming BCLK frequency limitations.
Fortunately, Asus’ Rampage III Formula is good enough. And with relatively little effort, 4 GHz is a piece of cake. It takes a little more ambition to get 4.2 or 4.3 GHz running stable. But even still, the 32 nm chip doesn’t run hot at all—I never saw the thing crest 80 degrees, even with 1.425 V applied to it. A combination of higher IOH voltage, an elevated PCIe clock, and lower QPI data rates are all viable strategies for breaking past that pesky BCLK wall so many enthusiasts run into.
Don’t expect boatloads of additional performance due to the extra 4 MB of L3 cache—in our testing, there were only a couple of instances where the overclocked Westmere-EP-based Xeon E5620 outperformed the Bloomfield-based Core i7 at 4 GHz (and that was with dissimilar memory clocks, so a couple of variables likely came into play).
What you can expect, though, is a processor that requires less voltage at 4 GHz and beyond than those based on the 45 nm process. Consequently, it runs less hot and consumes less power. For my money, I’d be far more comfortable with it in my own workstation, long-term, than a CPU running at 90+ degrees under load. For many overclockers, those attributes alone won’t be worth the $100 price premium Intel’s Xeon E5620 holds over its Core i7-930. For others, that $100 is far more palatable than an extra $600+ for the Core i7-970—the only enthusiast-class 32 nm CPU in the company’s desktop lineup.
With Sandy Bridge still months away, aimed at the mainstream, and largely inaccessible to the overclocking community (save a couple of K-series SKUs that’ll be marked up), the Xeon E5620 may very well be a viable choice for power users who just can’t wait for Intel to refresh its enthusiast platform late next year with LGA 2011.