RAM | Reseller Advocate Magazine: Issue 63

By William Van Winkle

Over the years, I've done a lot of benchmark testing on overclocked components, and some people would say that makes me an overclocking expert. I know gamers who take a lot of pride in water cooling their systems and running system monitors tied to blinged-out, rheostat-studded bay devices. Friends of these gamers consider them overclocking experts. But the reality is that I actually know enough about overclocking to appreciate that I'm not an expert. The dozens of options you can tweak just on memory timings in enthusiast board BIOSes leave me baffled. I can fumble my way through, but I'm a generalist at best. Many resellers I've spoken with are in the same boat, which is unfortunate.

Much as we assume that all of the enthusiast consumer business goes to Newegg and similar wholesalers, the fact is that this is not true. Many system builders base a lot of their business on enthusiasts. Additionally, there are what I might call "second-tier enthusiasts" who want the performance benefits of deep geekdom but don't have the time or inclination to haunt all of the necessary forums to gather that knowledge. They would rather trust a reseller to help guide them through those optimizations.

Quite simply, overclocking is an increasingly used tool, and it's a "feature" you should be treating as a value-add. Not trusting myself to make recommendations this time around, I went in search of the best expert I could find and ended up at Erik Cubbage, product marketing engineer at Intel. He's the person that Intel sends to gamer events as the resident board tweaking expert. Case in point: When the 2.93 GHz Core 2 Extreme X6800 first arrived, I tried to test its overclocking potential and topped out around 3.3 GHz. Cubbage has shown live demonstrations exceeding 4.0 GHz several times. He's the man.

I spent almost two hours on the phone with this performance guru. Up next is the Cliff's Notes version of our discussions , information that I hope you can use to bolster your street cred with enthusiast customers. Ready? We need to blow through this quickly...it's about overclocking, after all.

OC Basics

First, the obligatory disclaimer. Processors are like your brain, with transistors instead of brain cells. Like brain cells, CPU transistors die off during the course of use. It's natural, and the system design accommodates a fair amount of atrophy over time. Taking drugs can accelerate the rate of brain cell death; overclocking can accelerate transistor death. My uncle has been a scatterbrained pothead for almost 40 years, but he's still a perfectly functional doctor. Intel CPUs are rated to run at the stated specs 24x7 for seven years with no performance loss from transistor death. Say you constantly run a chip at a 20% overclock and it shaves two years off the CPU's lifespan. (There are no known simulations that show specific overclocking atrophy rates, by the way.) Will anybody care if a CPU runs for five years instead of seven when the average system turnover time is three years? Your call. Industry rumors about Intel refusing to replace parts from overclocking damage are bunk. It's cheaper for Intel to replace a part than diagnose why it failed. If you have a failed retail component under warranty, Intel will replace it. Period. That said, there are so many levels of safeguards now in place that the odds of a part failing from excessive overclocking are very slim. A CPU will shut down before it can burn up. Alternatively, it may downclock itself to run cooler. This is why you sometimes see benchmark results get slower the more you increase system settings. There's so much data corruption happening that the error correction and subsequent downclocking slaughter the test results.

There are two basic ways to overclock. The first is just a general preset that increases the major system buses by a given percentage. Historically, Intel motherboards have allowed for a "burn-in" mode of up to 10%, although the original BadAxe board (D975XBX) increased the burn-in ceiling to 30 percent. (AMD-based boards have been far more liberal, and AMD itself has been more lenient about not locking down certain CPU attributes in order to make them more enthusiast-friendly. This is why Intel is now faced with pounding the performance message at every turn, because the belief that AMD is the de facto gamer's pick remains rampant.) I've tested plenty of non-Intel enthusiast boards that ascribe catchy names to different preset overclocking percentages, but I've grown to dread these over time. Intel's 10% burn-in was so innocuous that it couldn't singe a fly, and many third-party OC presets leave you stuck in an endless reboot cycle with no idea what went wrong. Some boards have the decency to return you to default or "last known good" settings after a crash so you don't have to reset the BIOS, but this handy feature is far from universal.

Getting Advanced

Clearly, a more manual approach is preferable to a handful of general presets, but this is where newbies can get into trouble. To illustrate, let's say we're testing with a Core 2 Duo X6800, which is a 2.93 GHz part clocked at a front-side bus (FSB) speed of 266 MHz with a default multiplier of 11. (266 MHz multiplied by 11 equals 2.93 GHz.) Because our newbie is using an X6800 chip, and Extreme Edition parts feature unlocked multipliers, he decides to bump the multiplier to 12—no big deal. 266 times 12 equals 3.2 GHz, which is still just shy of a conservative 10% overclock. But the newbie doesn't pause to take in the big picture. He just adds on a front-side bus increase of 10%, pushing that 266 MHz to 292.6 MHz. This now brings us to an effective speed of just over 3.5 GHz, and the highest air cooled speeds Cubbage has ever seen from an X6800 after considerable tweaking is 3.6 GHz. So odds are that the system would fail at this point.

Moreover, it's common for owners of 667 MHz DDR2 performance memory to crank up their memory speeds to 800MHz. This is a 20% jump, which is hefty but not unreasonable for a premium module from the likes of OCZ or Corsair. However, that 10% nudge on the FSB also pulls the memory bus along with it, taking that 800 MHz up to 880 MHz for a total memory overclock of 32 percent. That's getting pretty dicey without some assisting changes to the system voltages.

Voltage adjustments are essential in serious overclocking—more speed requires more juice—but they're also what take the heaviest toll on transistor atrophy. There are no rules about excessive over-voltages, but the general guideline when trying to optimize a system is to target a 10% to 15% over-voltage on your CPU, memory, and northbridge components. For example, you might determine that the X6800, with a 12% over-voltage on the CPU, can hit 3.4 GHz, and a push to 15% will let it top out with stable running at 3.45 GHz. That's probably a good place to stop.

But we're skipping a step. Die-hard overclockers want freedom with their CPU multipliers because the best way to achieve the highest clock speeds is to start out by dropping the multiplier. The rough guideline is to drop the multiplier by two. Cubbage knows through extensive trial and error that the X6800 on a BadAxe 2 (D975XBX2) pulls in maximum results with a multiplier of 9, yielding an effective starting speed of only 2.4 GHz. Similarly, you want to drop the memory speed down a bin; 667 MHz modules (and perhaps even 800 MHz sticks) should knock down to 533 MHz. This leaves plenty of room to crank up the FSB settings, which is good because the front-side bus is far and away the most flexible bus in the PC.

With your multiplier dropped, memory bus speed reduced, and your voltages raised, next comes the process of inching up the FSB speeds. I can't describe to you the weeks of time I've spent doing benchmarking in which I'd pick a bus speed, run a test, reboot, increase the bus speed 5 MHz, and repeat the process over and over until the system failed, all in the name of overclocking. This arduous process was necessary because you can't just jump from 2.4 GHz to 4 GHz; you have to gently ease up toward it. Well, it turns out that Intel Extreme Series motherboards ship with a utility called Intel Desktop Control Center. In addition to being a nifty system monitor, this utility will ratchet up the FSB in 1 MHz to 2 MHz increments until the instability point is reached. The app can't control multiplier or voltage changes because those require a system reset, but still—the time savings provided by this tool are staggering.

Notes From the Trenches

As Erik Cubbage likes to describe it, there are advanced overclocking techniques, most of which are detailed above, and then there are "super-duper advanced techniques." These are just things a frequency aficionado picks up with years of practice. So, in no particular order, here are a few of his biggest super-duper observations and tips.

1) When overclocking, memory will often fail before the CPU. When it seems you've hit a ceiling, either give the memory a bit more voltage, ease up a pinch on the memory speed, or tweak the timings. If you're dealing with 4-4-4 module timings, try comparing the results of changing to 5-5-5 versus stepping down 5 MHz. For all the hoopla made over monkeying with memory timings, Cubbage says that he usually tests with the rated timings provided by the manufacturer, which can sometimes differ from what the module's SPD reports to the BIOS. Only at the end, when trying to eke out the last bit of speed, will he mess with timing changes.

2) While there may be some efficiencies inherent to having synchronous bus speeds between the CPU and memory, when it comes to overclocking all bets are off. Staying synchronous no longer matters. Your mission is simply to discover the maximum stable speeds your CPU and memory will tolerate separately.

3) Beware the video bottleneck. If your tests start to show a performance plateau beyond a certain speed setting, check the parameters of the testing app. Gaming benchmarks in particular are prone to running at high resolutions with lots of filtering enabled. This is great for testing the GPU, but the more you test the graphics, the less you test the CPU. Turn off the filtering and run at 800x600 or even VGA to see if that moves your test ceiling.

4) Work to max out your CPU first, then the memory, then your video card.

5) Effective cooling is essential to overclocking. The 4 GHz speeds Cubbage coaxed from that X6800 were only possible with liquid cooling. Cubbage recommends Astoria, OR-based Danger Den (www.dangerdenstore.com) as being the top provider of custom water cooling gear. Zalman (www.zalmanusa.com) remains the preeminent name in air cooling add-ons.

Blazing BadAxe

From here, the last primary concern in overclocking is component selection. As you've probably guessed, Cubbage and I are big fans of the BadAxe 2, but not just because it's Intel's flagship desktop board. Most competing boards founded on the 975X chipset were based on the original Intel reference design that circulated among third-party manufacturers. However, Intel's design team chucked the reference and built the D975XBX series from scratch.

"With BadAxe 2," says Cubbage, "we moved the CPU socket further away from the voltage regulator, and the farther away those two components are, the less you get electrical crosstalk interference. We also increased the thickness of the copper traces feeding power into the CPU by 50 percent versus a normal board. That fatter pipe gives you better reliability and helps you run smoother and cooler."

The D975XBX2 uses a voltage regulator that runs three to four times what a mainstream VREG costs in order to deliver more and cleaner power to the CPU. Unlike many competing boards, Intel here gives granular control over voltage settings, not to mention many other overclocking attributes, and finally dispenses with all arbitrary burn-in mode limits. You could crank the BIOS settings up by 700% if you liked.

Regardless of your brand choices, learn how to add value by maximizing your systems' performance. Pick the right components and show customers that you've got the know-how to help them get more bang for their buck.