I still remember the PC I owned back in 1998. It was based on a Pentium II 233 with Intel’s Deschutes core, dropped into an Asus P2B motherboard. That system was fast, but I was a bored engineering student and wanted to do more with it. I started with aftermarket air cooling. And although I don’t remember how much overclocking headroom I was able to realize, I do remember that it wasn’t enough. At one point, I pried the plastic cartridge away from the slot-mounted processor and started experimenting with Peltier coolers for better cooling performance. When the proverbial smoke cleared, I was running at a stable 400 MHz—as fast as the most expensive model available at the time, for significantly less money.
Of course, the overclocks today are a lot more significant than 166 MHz. But the principle remains the same: take a processor running at its default settings and squeeze additional value out of it by trying to match the performance of higher-end and more expensive models. With a little effort, it’s actually quite easy to get a sub-$300 Core i7-920 beyond the performance levels of a $1,000 Core i7-975 Extreme without obliterating its reliability.
What About “Auto-Overclocking?”
Overclocking, in general, has always been a bit of a sore subject with AMD and Intel, which officially have to discourage the practice with threats of voided warranties should your CPU show signs of manipulation. Publically, however, both vendors try to appear enthusiast-friendly by giving away overclocking software, facilitating aggressive BIOSes, and selling CPUs with unlocked clock multipliers. Despite those off-the-record endorsements, though, power users simply accept that there’s no such thing as a free lunch, and killing a CPU with too much voltage is sometimes just part of the game.
But with the introduction of Turbo Boost technology in Intel’s LGA 1366-based Core i7 and the subsequent debut of an even more aggressive implementation in the LGA 1156-based Core i5 and Core i7 processors, Intel took it upon itself to implement a form of intelligent overclocking based on a handful of different factors: voltage, amperage, temperature, and operating system P-state requests directly related to CPU utilization.
In monitoring each of those parameters, Intel’s onboard power control unit is able to augment performance by increasing clock rate in situations where the processor’s maximum TDP isn’t being reached. By essentially shutting down unused cores, thereby dropping power consumption, more headroom is freed up in single-threaded workloads, a little less when two threads are active, still less with three cores utilized, and so on. Thus, Intel’s “automatic overclocking” exists as an elegant, more granular way to increase performance without taking power consumption over the maximum TDP rating of any given CPU (130W in the case of Intel’s Bloomfields and 95W in the case of the Lynnfields).
Can You Do Better?
The question we asked ourselves—especially after seeing that the Core i7-860 and -870 would accelerate a fantastic 667 MHz in single-threaded apps—was whether it was still worth it for the power user to go all-out with processor overclocking and risk nuking a perfectly good CPU, or simply let Intel’s version of the technology handle business? I hoped that I wasn’t just getting lazy in my old(er) age, and that there’d still be palpable gains to taking the enthusiast’s path to better performance. But I also wasn’t ready to dismiss the efforts Intel’s engineers made in optimizing Nehalem for balanced performance in single- and multi-threaded software.
We decided to run a little experiment: take a Core i5-750 and Core i7-860, overclock each, and compare the results to what the two processors can do with Turbo Boost enabled, and then disabled. Of course, we have samples from Intel here in the lab, but we can’t really believe that those are representative of retail models. So we bought both chips off of Newegg, just to be sure. While we debated sticking with Intel’s retail cooling solution, at the end of the day it was decided that we’d never seen 4 GHz if we didn’t augment the reference heatsink. Thus, all of our testing is done with Thermalright’s MUX-120, too.