Overclocking AMD

AMD’s low- and midrange procs, such as the Athlon 64 X2 6000+ we’re using here, are great values made even better by pusihing them to new heights. Got a Phenom? The steps are pretty much the same

Step 1: Back Up Your Data

Overclocking is inherently risky, so back up your data. We mean it.

Step 2: Enter Your Bios

Get into your BIOS by hitting the Del, F1, or F2 key during boot. The key will vary by motherboard, so check your documentation if you’re not sure what to press. Once in the BIOS, you will need to find the appropriate configuration screens for overclocking. The screens we refer to in our examples are specific to the Asus M2N32-SLI motherboard, but they will differ from BIOS to BIOS. Your mobo manual or an online search can provide guidance, but often you just need to dig around. 

Step 3: Increase Your CPU’s Multiplier

Your choices for overclocking are determined by your proc. AMD’s FX-grade CPUs, like Intel’s Extreme chips, are unlocked and let you alter their multiplier settings. AMD recently began unlocking its Black Edition procs as a concession to overclockers who have stuck with the platform. Increasing the multiplier makes for a no muss, no fuss overclock. On our Asus M2N32-SLI board, we go into Advanced JumperFree Configuration and find CPU Multiplier. Our Athlon 64 X2 6000+ is locked, and thus can’t exceed its stock setting of 15x. If your chip is unlocked, you can select a higher multiplier. To get an Athlon 64 FX-60 from 2.6GHz to 2.8GHz, you would need to increase the multiplier from 13x to 14x. Next, test your system for stability. If it crashes or won’t boot, see Step 8.

Step 4: Meet the HyperTransport Link

There’s an overclocking alternative to altering a chip’s multiplier setting. If this were an Intel platform, we’d turn our efforts to the front-side bus and be instantly overclocking, but AMD’s design is a little more complicated. You’ll need to futz with the HyperTransport (HT) speed before you overclock. This interface between the CPU and chipset buzzes along at about 1GHz and doesn’t like to get too far out of spec. Often, people who overclock without reducing the HT speed confuse HT instability with CPU instability. To lower the HT link on our M2N32-SLI board, we go into the BIOS and drill down through the Advanced and Chipset menus. There we see a setting for CPU<->NB HT Speed. Our choices are 1 through 5 and Auto. The default is 5x 200, or 1,000MHz. Since this value will increase during the overclock, knocking it back to 4x (800MHz) or even 3x (600MHz) shouldn’t hurt performance. Keep in mind that when you overclock the CPU frequency, you overclock the HT as well. If, for example, you overclock your CPU frequency to 220MHz and are running a 4x multiplier on your HyperTransport link, you’ll actually be running an 880MHz HT. Set it at a lower speed and prepare to overclock.

Step 5: Boost Your Frequencies

Now it’s time to overclock that sucker. On our M2N32-SLI board, we go to Advanced, JumperFree Configuration, and open CPU Frequency. There, we’re greeted by settings of 200MHz and up. We can bump the frequency up to 210MHz, which when multiplied by 15x (the CPU’s multiplier setting), gives us an overall speed of 3.1GHz. Another bump up to 220MHz gives us 3.3GHz. We recommend you increase speeds by 10MHz increments, testing for stability after each jump. If your machine crashes or fails to reboot, see Step 8.

Step 6: Add Voltage

In some cases, boosting the voltage to your CPU can help stabilize an overclock that’s crashing. Unfortunately, this is one of the more dangerous aspects of CPU overclocking as overvolting a chip could kill it. On our M2N32-SLI board, we went into Advanced, JumperFree Configuration and changed the CPU voltage from Auto to 1.5 volts. That’s about a tenth of a volt out of spec, but unfortunately for us, it didn’t help us sustain a 3.3GHz clock speed, so we’re stuck at 3.28GHz. 

Step 7: RAM Divisors

With AMD CPUs, the RAM is linked to the clock setting, and the Athlon 64’s on-die memory controller supports only whole numbers for memory divisors. So a 3GHz Athlon 64 X2 6000+ can use either a 7 or 8 divisor to generate a signal for the RAM. Unfortunately, 3,000 divided by 7 works out to DDR2/857 and 3,000 divided by 8 works out to DDR2/750. AMD errs on the side of caution, so this processor actually runs the DDR2/800 at 750MHz. But when you overclock, you may inadvertently overclock the RAM further than you suspect. The 3.28GHz we achieved on our M2N32-SLI board, for example, runs the DDR2/800 slightly out of spec at 825MHz. That’s not something to worry about, but if you’re running your chip at much higher speeds than us, you’ll need to make sure the RAM isn’t running beyond what its maker guarantees. To do that, go into Advanced, CPU Configuration, DRAM configuration, and then Memory Clock Frequency. You should select a conservative low speed for now and clock it up after you’ve reached the CPU’s highest speed.

Step 8 : It Won’t Boot

Don’t be bummed if your machine hard-locks—it’s the only way you’ll learn your CPU’s limits. To get out of the hole, shut off the PSU or pull the plug from the wall for five seconds. Plug it back in and power up the box. Some boards will automatically recover from a bad overclock and let you go back into the BIOS to aim a little lower. If this doesn’t work, you’ll have to power down again, unplug the PSU, and reset the CMOS via a jumper or button, or by pulling and reinserting the coin-cell battery. After five seconds, try booting it again—you should be able to access the BIOS. 

Step 9: Test It

Getting into the OS is about 65 percent of the challenge. You’ll now need to test the machine by pushing the CPU with an intensive workload. We don’t recommend gaming as a test since games are typically GPU-bound. Try a video encode or run Prime95. And if you have a multi- or dual-core processor, run a multithreaded app.

Keeping Your CPU Cool

Without adequate cooling, your overclocked rig is as good as toast

It’s hard to get much worse than a stock air cooler for your CPU. That’s not to say there’s anything outright wrong with the fan/heatsink combo that comes with a new CPU—the little guy will likely keep your stock-clocked processor running well within safe operating temperatures.

The minute you start overclocking your processor, however, you’ll be jacking up your thermals to levels a stock cooler can’t handle. Granted, when overclocking, temps will go up with even premium air coolers, but a solid aftermarket device will give you more room to work with. Your initial temperatures will be lower, and they won’t rise as quickly as they would with a stock solution.

Our current Lab champion, Zalman’s CNPS9700, has maintained the throne for nearly a year. It uses a copper and aluminum framework to absorb the warmth produced by both Intel and AMD CPUs. The cooler’s 2,800rpm fan emits a tornado-like whoosh when it’s cranked to the max, but it also allows the device to reach epic levels of heat reduction. In fact, we now use the Zalman as a benchmark for other coolers. On the last test we ran, the device took our processor down to 37.5 C during our CPU burn-in test and 22.5 C when idle—a savings of 16.5 C and 9.5 C, respectively, over stock.

Aftermarket air cooling is a fine way to manage CPU temperatures, but only to a point. Eventually, practicality and performance concerns render air coolers insufficient for OC’d machines. That’s why there’s liquid cooling. Not only can you reach lower temperatures when using a liquid-based setup as opposed to air, but you’ll also benefit from a lower sound profile.

Of course, there’s an obvious caveat: Liquids plus electronics can equal a serious monetary hit if you have to replace hardware that inadvertently gets wet. Installing a water-cooling kit in your rig is a delicate process, and the drama only increases if you’ve never done it before. Sure, you can go with a preassembled liquid-cooling kit, but in our experience, a majority of these units perform on par with—if not worse than—stock air coolers.

The best liquid cooler we’ve found is CoolIT’s Boreas unit. A fancier, fatter version of the company’s Eliminator, the Boreas uses 12 thermoelectric modules to rip the heat from your molten tubing into a giant heatsink. Two 12cm fans take care of the rest, allowing the Boreas to beat our FX-60 test bed’s stock cooler by 20 C in idle and 32 C during our burn-in test.

Overclock an OEM Machine

So, you’re ready to crack open your business-class Dell, HP, or Gateway and give it some gusto, eh? Fugetabout it. The overwhelming majority of OEM machines and notebook PCs prevent overclocking to reduce complaints from the chumps who OC recklessly and ruin their machines. Even motherboard brands known for overclocking may be neutered in an OEM machine. Got it? OK, now we’re going to contradict ourselves. Some OEM boxes do overclock. Dell’s XPS and Hewlett-Packard’s Blackbird PCs are designed to overclock. Still, for the most part, overclocking and OEM machines don’t mix. 

Do RAM coolers help overclockers?

Plenty of folks have taken overclockable RAM to its limits without the aid of aftermarket cooling devices, so why buy one? RAM coolers help, but not in the direct and immediate way a better CPU heatsink does. Overclocked RAM is pushed way beyond standard voltage. For example, a DDR2/1250 module from Corsair is spec’d to run at 2.4 volts—a far cry from a standard 1.8-volt DDR2 part. With the extra voltage comes additional heat generation and a potentially shortened life. Adding a RAM cooler or simply increasing the airflow in your case (especially if the modules sit above hot graphics cards) can only help extend your RAM’s life.