Overclock Your PC

Posted 12/31/2007 at 1:49pm | by Gordon Mah Ung and David Murphy

3

Comments

Print

Overclocking AMD

While we wait for AMD to launch its new high-end part, we can push its low- and midrange procs, such as the
Athlon 64 X2 6000+ we use here, to new heights.

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.

Performed on an EVGA 680i SLI mobo, 2GB Corsair Dominator 8500 RAM, a PC Power and Cooling 1KW PSU, and standard air cooling.

Next: Keeping Your CPU Cool!