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xXxexpertxXx · 03-09-2008, 03:03 AM

Thought this would be helpful!

Maybe Sticky??

Once upon a time, overclocking was considered a risky and dangerous thing to do. Only the edgiest computer outlaw would even consider such practice. It was believed that you could easily damage your PC's components completely. It was frowned upon by parts manufacturers. It was, in a word, crazy.

Overclocking gradually came into the mainstream throughout the late 1990's. We know, because we were covering it back then (albeit in different publications). One of the first overclocking articles, circa 1997, was a simple editorial saying how dangerous it could be, but that you might gain some performance. Some time later we wrote a feature with details on how to overclock a CPU, but it is laden with warnings (you could blow a chip! You'll void your warranties!)

How far we've come.

Today, overclocking is so commonplace that equipment vendors expect you to do it. Look, for instance, at AMD and Intel: Their enthusiast-class parts are completely unlocked and primed for a clock jump. Look at some memory vendors: OCZ, for one, allows a 5% overclock on some of its memory without voiding the warranty. Look at Nvidia and AMD's ATI: Overclocking controls are downloadable from their sites, or built right into their driver interfaces.

Way back when, it was insane to overclock your computer. Now, it's almost insane not to

Why Overclock? Performance Comparisons

The urge for most of us to overclock our PC's equipment is simple: There's no good reason not to. Most gear will overclock, at least slightly, without any special cooling, so overclocking is free except for the time spent doing it. Factor in the performance gain, and overclocking becomes a free upgrade to a superior product. What's not to love?

Normally, we run our performance charts late in our features. For this one, we're tossing them at you early. Here is why we overclock.

These perf charts show several things. There's the PC running at spec. There's the PC with one item overclocked, three times: the CPU, the memory, and the graphics card. Then there's the PC with the net result of overclocking all of those components at once. Read these charts knowing that the overclocks they show are modest ones, and they're up just for the sake of argument:

Why overclock? Because if this is a minimal performance gain, imagine what you could do if you really pushed your stuff!

ExtremeTech Overclocking Guide
discuss Discuss this now (13 posts)

Why Overclock? Performance Comparisons

The urge for most of us to overclock our PC's equipment is simple: There's no good reason not to. Most gear will overclock, at least slightly, without any special cooling, so overclocking is free except for the time spent doing it. Factor in the performance gain, and overclocking becomes a free upgrade to a superior product. What's not to love?

Normally, we run our performance charts late in our features. For this one, we're tossing them at you early. Here is why we overclock.

These perf charts show several things. There's the PC running at spec. There's the PC with one item overclocked, three times: the CPU, the memory, and the graphics card. Then there's the PC with the net result of overclocking all of those components at once. Read these charts knowing that the overclocks they show are modest ones, and they're up just for the sake of argument:

Why overclock? Because if this is a minimal performance gain, imagine what you could do if you really pushed your stuff!

Our overclocking PC's pertinent specs are:

CPU Intel Core 2 E6750
Memory 2GB Corsair CM2X1024-10000C5D
Graphics ATI Radeon HD 2600 XT
Audio SoundBlaster X-Fi Extreme Gamer
Hard drive Seagate ST3320620AS (320GB 7200.10)
Optical drive Sony DVD+/-RW

First, look at the synthetic charts

http://common.ziffdavisinternet.com/...=189527,00.gif

http://common.ziffdavisinternet.com/...=189530,00.gif

When you focus on an individual component overclocked, the gain isn't spectacular, but it's definitely noticeable. Note that overclocking the CPU affects PCMark05 more than it does 3DMark06, and overclocking the graphics card has the opposite effect.

Gaming benefits depend on whether the game performance is bound by the processor or graphics card. We present two game benchmarks: Supreme Commander, which is a very CPU-bound game full of physics and velocity/vector computations (unlike most real-time strategy games, all the bullets shot in SupCom are physically modeled, and only hit their targets if a collision is detected).

Then there's Company of Heroes, which is largely 3D bound. The benchmark doesn't do much in the way of AI or physics computations, as it doesn't actually show gameplay; it's just a pre-scripted scene. We've presented a pair of charts for COH for both DX9 and DX10.

http://common.ziffdavisinternet.com/...=189531,00.gif

http://common.ziffdavisinternet.com/...=189532,00.gif

http://common.ziffdavisinternet.com/...=189533,00.gif

Each game shows gains. Thus, you can see that overclocking your computer's components shows real, tangible benefits.

Finally, the warnings. Let's turn the question around: why not overclock?

There are a few reasons. First, in some cases, a component might not be inherently overclockable. It depends not only on the part, but on the stepping. Some CPUs might show terrific gains, but others might put up a fight for a measly five percent overclock.

Second, in many cases, you still do void the warranties when you overclock a part. It depends on the manufacturer's policy on the subject.

Third, if you get into tweaking not only clock frequencies, but also voltages, you can permanently damage a part, or even an entire motherboard.

Forth, and finally, overclocking is time consuming. You need an entire afternoon—or even an entire weekend—to do it properly. If you spend a few minutes tweaking settings, you might get a small gain, but to push your gear to the limits, you need time to tweak, time to burn in, time to reset the CMOS and start over, and time to do it all over again. And again.

Now let's take a look at knowing what's overclockable.

Knowing What's Overclockable

Before you tear into your parts, you should spend some Web time doing research to see just how overclockable your components are. Doing so could save you a lot of time and energy.

Basically, you can overclock three major components of your PC: the CPU, the memory, and the graphics card. Some people also tweak the clock frequencies of their motherboard's various buses and links, should the motherboard's BIOS setup program offer the option.

The CPU's overclockability depends on its model and its stepping. Most enthusiast-level chips from Intel and AMD (the "extreme" series from Intel, and the FX series from AMD) are pretty easy to overclock. Other chips may or may not be.

The stepping really does matter, too. One batch of a particular Core 2 Duo chip might have an incredible amount of headroom, but the next batch might be pretty tight.

In terms of memory, the overclocking capacity depends on its native frequency, the manufacturer, and the quality. If you're running DDR2-1066 memory in a motherboard that only supports DDR2-800 memory, overclocking won't be a problem because the memory has built-in headroom. If, however, you plan to run memory at a higher frequency than its native, you'll need high quality RAM from a trusted manufacturer like Corsair, Mushkin, OCZ, or Crucial. Stay away from generic memory.

A graphics card is almost always overclockable to some extent, but one with a big, juicy, aftermarket cooler is probably more overclockable than one with the reference cooler. That brings us to our next subject: heating and cooling.

The biggest enemy of an overclocker, besides maybe an uncooperative stepping, is heat. Heat causes chips to fail. Failing chips cause spontaneous hangs, reboots, graphical anomalies, and, in some cases, data corruption.

When you overclock a processor, it gets even hotter than it normally runs—and most CPUs and GPUs run very hot to begin with. Turning up the frequency makes the transistors work faster, and thus they generate more heat.

It's unlikely that simply overclocking a chip will destroy it. Most CPUs, or at least their motherboards, have failsafes built in to shut down the system when they get too hot. GPUs might simply stop responding. What might happen, however, is the shortening of the overall life of the chip through the gradual breakdown of the elements that make up the transistors. However, it's far more likely that the chip will become obsolete long, long before it dies.

You can, and should keep the affected parts cool when you overclock. Sometimes, the bare minimum, stock cooler (usually a heat sink and fan) are sufficient. This is especially evident with recent GPUs, whose coolers cause the cards to be double-wide; the cooling is so efficient that they've stalled the cottage industry of aftermarket GPU coolers for self-installation. CPU cooling is a different matter, though. The stock coolers that come with Intel and AMD chips are made for spec frequencies, so you'll need a much better cooler to expect any gains from overclocking before the system locks up.

Air, liquid, and thermo-electric cooling are all options. All three have gotten easier to install and cheaper to buy over the years. Keep an eye on reviews—on this site and others—to help you pick the best cooler.

Note that some hardcore overclockers even go the way of refrigeration, but that gets overwhelmingly expensive and complicated.

Just for fun: here's a breakdown of the heat generated by the system we modestly overclocked:

The Overall Overclocking Technique

Before disclosing the basic overclocking technique that works for everything, there's one word we really want you to become familiar with: stability.

The key to a successful overclock is being able to use the computer when you're done. That means, you can play games, crunch numbers, transcode video, sync your iPod, or whatever, without the PC locking up, crashing, or suddenly rebooting. If the PC isn't stable, your overclock is a failure.

Anyone can say they got their 2.66GHz CPU up to 4.09GHz with the stock cooler if all it did was POST before it crashed, or even if all it did was run Windows but crashed when you moved the mouse. We're going to talk about stability testing, which is one of the necessary steps of overclocking. Passing a stability test is mandatory before you can say you've overclocked anything.

Our technique for overclocking any part (we'll get into specifics later) is simple:

1. Tweak
2. Boot
3. Test
4. Repeat

That's it. Easy, right? Let's give a little more detail:

1. Tweak. Raise the clock frequency just a small amount. Overclocking requires baby steps. If you're overclocking a multiplier-unlocked CPU, raise it one number at a time. Raise the FSB maybe five to ten megahertz at a time. Same with the graphics core and/or memory. And also, don't change two settings at once.
2. Boot the system. Watch as it boots. Does it POST? Is the RAM count correct? Does the boot take longer than it usually does? Watch for any signs that your computer isn't acting normally; they could be signs of instability.
3. Test. Run a stability test. We usually test CPUs and memory with Prime95 (running one instance per core) for 30 minutes. We test GPUs by playing a nice, long session of a very recent, graphically intense game.
4. Repeat. In other words, return to step 1. If the overclock passes your stability test, raise the frequency or multiplier another notch.

If Step 3 fails, drop back a notch and run the stability test again. Once you've found the absolute fastest frequencies your computer's components can run, you've completed your overclocking experiment.

Here are a few things to be aware of:

* When you overclock a PC, it's never truly stable. The PC was not designed to run with different things at different clock rates that aren't necessarily compatible with each other. What you gain in performance you lose in piece of mind: This thing could crash at any moment.
* Never overclock a PC with important data on it. Overclocking affects the memory and the CPU, and those in turn affect data written on the hard drive. Overclocking can end with corrupted data. You could lose stuff. Keep your overclocking relegated to gaming machines, graphics workstations—anything except a PC with mission-critical or personally-valuable data on it.
* To get Prime95 to run on multiple cores, you must first tweak the desktop shortcut and then tweak the running program. First, open the desktop shortcut properties sheet and the command line switch Ax to the end of the Target box, where x = the number of instances you need to run (2 for a dual-core, 4 for a quad-core, etc.) Then, launch the program as many times as you need. Finally, in each instance of the program, click Advanced, go to Affinity, and the Specific CPU to run on box, enter 0 for the first core in the first instance and click OK; 1 for the second core in the second instance; and so on. Then you can start your CPU torture tests.

http://common.ziffdavisinternet.com/...=189535,00.jpg

# When torture-testing the CPU, monitor the temperature with whatever monitoring tool came with your motherboard (e.g. ASUS offers PC Probe II with current boards). If you don't have a monitoring tool, go to the motherboard's manufacturing page, find the downloads for your specific motherboard, and download the utility.
# If you overclock too high and the PC won't POST, you have to reset the CMOS. There's usually a switch or a jumper on the motherboard specifically for this purpose. If, for some reason, the switch or jumper doesn't work, or there isn't one at all, power down the PC, unplug it, open the case, and pop out the small, round, disc-shaped battery for about ten minutes. Then, replace it and power back up. The BIOS setup program will be at pure defaults.
# Although we purchased a power meter and tested, overclocking doesn't raise the amount of voltage a power supply draws from the wall. The machine with the specs listed above, at idle, drew 119W before overclocking, and drew 120W while overclocked at 10% over spec.

Overclocking a CPU

First off, let's get this out of the way: There are utilities that allow you to overclock a CPU through a Windows desktop.

Ignore them.

Many times we have used such a utility, rebooted, and encountered a machine unable to POST. Do your overclocking through the BIOS setup utility. Trust us.

There are two ways to overclock some CPUs, but others only offer one way. Extreme-edition Intel Core-2 and Pentium CPUs, and AMD FX CPUs, allow you to tweak the multiplier. All other CPUs require you to tweak the FSB. FSB stands for front-side bus. AMD doesn't have an FSB. We're using FSB as an umbrella term for ease of writing this article.

A CPU's frequency is the core frequency of the FSB (before it's multiplied by four, because FSB's are "quad-pumped"), times the CPU multiplier. Thus, a CPU with a multiplier of 8, on a 1333MHz FSB would be a 2.66GHz CPU (1333 / 4 = 333.25 x 8 = 2666, or around 2.66) Note that lots of stuff gets rounded when determining these numbers.

If we then raise the multiplier to 10, the CPU's frequency is now 3.33GHz. (333MHz x 10 = 3330MHz or 3.33GUz). That, if stable, is a fairly decent overclock.

For the overclock benchmarked earlier, we raised the FSB. Or, if we raise the core FSB frequency from 333MHz to 366MHz (thus raising the quad-pumped core to an effective 1464MHz, and the CPU frequency to 2.96GHz.

To sum up, raising either the FSB or the CPU multiplier overclocks the CPU.

Most BIOS setup programs allow you to do either. Look for an overclocking interface in the setup program. It should be there somewhere; sometimes it's under Advanced, but often it gets its own heading or page. We can't tell you where it is on your motherboard because there are no standards whatsoever on how a BIOS setup program may be designed.

http://common.ziffdavisinternet.com/...=189536,00.jpg

Raising CPU and Memory Voltage and Overclocking Memory

Sometimes, you actually have to increase the voltage, going to a part in order to successfully overclock it. If you've pushed a component too fast and the PC won't POST, before moving it a step back, raise its voltage ever so slightly.

This requires a bit of research, as different CPUs and memory modules have different voltages.

Raise voltage sparingly, and only one selection at a time. Too much voltage is one of the rare things that actually can kill a component dead. We make it a rule of thumb never to raise voltage more than 15%; if a component needs more than that for a successful overclock, we're not interested.

Overclocking Memory
You might inadvertently overclock the memory on a PC just by overclocking the CPU. The memory is usually tied right into the FSB, but some CPUs separate it. This is often referred to "linked" or "unlinked;" If the RAM is tied to the FSB in your motherboard, it's linked; if you can separate them and overclock them separately, you can unlink the RAM.

If the RAM will unlink, you should definitely overclock it separately. That way, the memory overclocking won't interfere with the CPU overclocking.

If you must overclock the memory via the FSB, you need to balance what the memory and the CPU are capable of together. This doesn't necessarily change anything; just follow the procedure carefully.

Overclocking a Graphics Card

Overclocking a graphics card is usually a simple matter of wielding two software-based sliders. Unlike memory and CPU overclocking, you can and should overclock graphics cards in Windows (or whatever OS you're running).

ATI's graphics card drive interface has ATI Overdrive, the overclocking page, built right in. For Nvidia, you have to download Ntune to grab its overclocking sliders. Since the interfaces are very similar, we're not going to show both. Shown, therefore, is ATI's interface.

To overclock the graphics card, simply slide the slider to the right.

http://common.ziffdavisinternet.com/...=189537,00.jpg

Use the technique described above; except you don't have to reboot. Slide a notch over a little, test, and repeat. That's all there is to it. First tackle the core frequency, find its max, and then find the max you can overclock the memory frequency.

Conclusion: Upgrade Your PC for Free

Now you know the basic steps to overclocking your CPU, memory, and graphics card. Depending on the motherboard, there might be a lot more about your own computer's BIOS setup program to learn. Some allow you to adjust the very core of the FSB frequency, for example; which throws one more control into the CPU/memory overclocking mess. Others let you delve into the timings of the memory's latencies, but that, technically, isn't overclocking (there's no clock frequency involved, but instead there are wait states to play with).

ExtremeTech - Deep technology for enthusiasts and professionals

03-09-2008, 03:03 AM	#1 (permalink)
xXxexpertxXx True Techie Join Date: Feb 2008 Posts: 227	Overclocking Guide Thought this would be helpful! Maybe Sticky?? Once upon a time, overclocking was considered a risky and dangerous thing to do. Only the edgiest computer outlaw would even consider such practice. It was believed that you could easily damage your PC's components completely. It was frowned upon by parts manufacturers. It was, in a word, crazy. Overclocking gradually came into the mainstream throughout the late 1990's. We know, because we were covering it back then (albeit in different publications). One of the first overclocking articles, circa 1997, was a simple editorial saying how dangerous it could be, but that you might gain some performance. Some time later we wrote a feature with details on how to overclock a CPU, but it is laden with warnings (you could blow a chip! You'll void your warranties!) How far we've come. Today, overclocking is so commonplace that equipment vendors expect you to do it. Look, for instance, at AMD and Intel: Their enthusiast-class parts are completely unlocked and primed for a clock jump. Look at some memory vendors: OCZ, for one, allows a 5% overclock on some of its memory without voiding the warranty. Look at Nvidia and AMD's ATI: Overclocking controls are downloadable from their sites, or built right into their driver interfaces. Way back when, it was insane to overclock your computer. Now, it's almost insane not to Why Overclock? Performance Comparisons The urge for most of us to overclock our PC's equipment is simple: There's no good reason not to. Most gear will overclock, at least slightly, without any special cooling, so overclocking is free except for the time spent doing it. Factor in the performance gain, and overclocking becomes a free upgrade to a superior product. What's not to love? Normally, we run our performance charts late in our features. For this one, we're tossing them at you early. Here is why we overclock. These perf charts show several things. There's the PC running at spec. There's the PC with one item overclocked, three times: the CPU, the memory, and the graphics card. Then there's the PC with the net result of overclocking all of those components at once. Read these charts knowing that the overclocks they show are modest ones, and they're up just for the sake of argument: Why overclock? Because if this is a minimal performance gain, imagine what you could do if you really pushed your stuff! ExtremeTech Overclocking Guide discuss Discuss this now (13 posts) Why Overclock? Performance Comparisons The urge for most of us to overclock our PC's equipment is simple: There's no good reason not to. Most gear will overclock, at least slightly, without any special cooling, so overclocking is free except for the time spent doing it. Factor in the performance gain, and overclocking becomes a free upgrade to a superior product. What's not to love? Normally, we run our performance charts late in our features. For this one, we're tossing them at you early. Here is why we overclock. These perf charts show several things. There's the PC running at spec. There's the PC with one item overclocked, three times: the CPU, the memory, and the graphics card. Then there's the PC with the net result of overclocking all of those components at once. Read these charts knowing that the overclocks they show are modest ones, and they're up just for the sake of argument: Why overclock? Because if this is a minimal performance gain, imagine what you could do if you really pushed your stuff! Our overclocking PC's pertinent specs are: CPU Intel Core 2 E6750 Memory 2GB Corsair CM2X1024-10000C5D Graphics ATI Radeon HD 2600 XT Audio SoundBlaster X-Fi Extreme Gamer Hard drive Seagate ST3320620AS (320GB 7200.10) Optical drive Sony DVD+/-RW First, look at the synthetic charts http://common.ziffdavisinternet.com/...=189527,00.gif http://common.ziffdavisinternet.com/...=189530,00.gif When you focus on an individual component overclocked, the gain isn't spectacular, but it's definitely noticeable. Note that overclocking the CPU affects PCMark05 more than it does 3DMark06, and overclocking the graphics card has the opposite effect. Gaming benefits depend on whether the game performance is bound by the processor or graphics card. We present two game benchmarks: Supreme Commander, which is a very CPU-bound game full of physics and velocity/vector computations (unlike most real-time strategy games, all the bullets shot in SupCom are physically modeled, and only hit their targets if a collision is detected). Then there's Company of Heroes, which is largely 3D bound. The benchmark doesn't do much in the way of AI or physics computations, as it doesn't actually show gameplay; it's just a pre-scripted scene. We've presented a pair of charts for COH for both DX9 and DX10. http://common.ziffdavisinternet.com/...=189531,00.gif http://common.ziffdavisinternet.com/...=189532,00.gif http://common.ziffdavisinternet.com/...=189533,00.gif Each game shows gains. Thus, you can see that overclocking your computer's components shows real, tangible benefits. Finally, the warnings. Let's turn the question around: why not overclock? There are a few reasons. First, in some cases, a component might not be inherently overclockable. It depends not only on the part, but on the stepping. Some CPUs might show terrific gains, but others might put up a fight for a measly five percent overclock. Second, in many cases, you still do void the warranties when you overclock a part. It depends on the manufacturer's policy on the subject. Third, if you get into tweaking not only clock frequencies, but also voltages, you can permanently damage a part, or even an entire motherboard. Forth, and finally, overclocking is time consuming. You need an entire afternoon—or even an entire weekend—to do it properly. If you spend a few minutes tweaking settings, you might get a small gain, but to push your gear to the limits, you need time to tweak, time to burn in, time to reset the CMOS and start over, and time to do it all over again. And again. Now let's take a look at knowing what's overclockable. Knowing What's Overclockable Before you tear into your parts, you should spend some Web time doing research to see just how overclockable your components are. Doing so could save you a lot of time and energy. Basically, you can overclock three major components of your PC: the CPU, the memory, and the graphics card. Some people also tweak the clock frequencies of their motherboard's various buses and links, should the motherboard's BIOS setup program offer the option. The CPU's overclockability depends on its model and its stepping. Most enthusiast-level chips from Intel and AMD (the "extreme" series from Intel, and the FX series from AMD) are pretty easy to overclock. Other chips may or may not be. The stepping really does matter, too. One batch of a particular Core 2 Duo chip might have an incredible amount of headroom, but the next batch might be pretty tight. In terms of memory, the overclocking capacity depends on its native frequency, the manufacturer, and the quality. If you're running DDR2-1066 memory in a motherboard that only supports DDR2-800 memory, overclocking won't be a problem because the memory has built-in headroom. If, however, you plan to run memory at a higher frequency than its native, you'll need high quality RAM from a trusted manufacturer like Corsair, Mushkin, OCZ, or Crucial. Stay away from generic memory. A graphics card is almost always overclockable to some extent, but one with a big, juicy, aftermarket cooler is probably more overclockable than one with the reference cooler. That brings us to our next subject: heating and cooling. The biggest enemy of an overclocker, besides maybe an uncooperative stepping, is heat. Heat causes chips to fail. Failing chips cause spontaneous hangs, reboots, graphical anomalies, and, in some cases, data corruption. When you overclock a processor, it gets even hotter than it normally runs—and most CPUs and GPUs run very hot to begin with. Turning up the frequency makes the transistors work faster, and thus they generate more heat. It's unlikely that simply overclocking a chip will destroy it. Most CPUs, or at least their motherboards, have failsafes built in to shut down the system when they get too hot. GPUs might simply stop responding. What might happen, however, is the shortening of the overall life of the chip through the gradual breakdown of the elements that make up the transistors. However, it's far more likely that the chip will become obsolete long, long before it dies. You can, and should keep the affected parts cool when you overclock. Sometimes, the bare minimum, stock cooler (usually a heat sink and fan) are sufficient. This is especially evident with recent GPUs, whose coolers cause the cards to be double-wide; the cooling is so efficient that they've stalled the cottage industry of aftermarket GPU coolers for self-installation. CPU cooling is a different matter, though. The stock coolers that come with Intel and AMD chips are made for spec frequencies, so you'll need a much better cooler to expect any gains from overclocking before the system locks up. Air, liquid, and thermo-electric cooling are all options. All three have gotten easier to install and cheaper to buy over the years. Keep an eye on reviews—on this site and others—to help you pick the best cooler. Note that some hardcore overclockers even go the way of refrigeration, but that gets overwhelmingly expensive and complicated. Just for fun: here's a breakdown of the heat generated by the system we modestly overclocked: The Overall Overclocking Technique Before disclosing the basic overclocking technique that works for everything, there's one word we really want you to become familiar with: stability. The key to a successful overclock is being able to use the computer when you're done. That means, you can play games, crunch numbers, transcode video, sync your iPod, or whatever, without the PC locking up, crashing, or suddenly rebooting. If the PC isn't stable, your overclock is a failure. Anyone can say they got their 2.66GHz CPU up to 4.09GHz with the stock cooler if all it did was POST before it crashed, or even if all it did was run Windows but crashed when you moved the mouse. We're going to talk about stability testing, which is one of the necessary steps of overclocking. Passing a stability test is mandatory before you can say you've overclocked anything. Our technique for overclocking any part (we'll get into specifics later) is simple: 1. Tweak 2. Boot 3. Test 4. Repeat That's it. Easy, right? Let's give a little more detail: 1. Tweak. Raise the clock frequency just a small amount. Overclocking requires baby steps. If you're overclocking a multiplier-unlocked CPU, raise it one number at a time. Raise the FSB maybe five to ten megahertz at a time. Same with the graphics core and/or memory. And also, don't change two settings at once. 2. Boot the system. Watch as it boots. Does it POST? Is the RAM count correct? Does the boot take longer than it usually does? Watch for any signs that your computer isn't acting normally; they could be signs of instability. 3. Test. Run a stability test. We usually test CPUs and memory with Prime95 (running one instance per core) for 30 minutes. We test GPUs by playing a nice, long session of a very recent, graphically intense game. 4. Repeat. In other words, return to step 1. If the overclock passes your stability test, raise the frequency or multiplier another notch. If Step 3 fails, drop back a notch and run the stability test again. Once you've found the absolute fastest frequencies your computer's components can run, you've completed your overclocking experiment. Here are a few things to be aware of: * When you overclock a PC, it's never truly stable. The PC was not designed to run with different things at different clock rates that aren't necessarily compatible with each other. What you gain in performance you lose in piece of mind: This thing could crash at any moment. * Never overclock a PC with important data on it. Overclocking affects the memory and the CPU, and those in turn affect data written on the hard drive. Overclocking can end with corrupted data. You could lose stuff. Keep your overclocking relegated to gaming machines, graphics workstations—anything except a PC with mission-critical or personally-valuable data on it. * To get Prime95 to run on multiple cores, you must first tweak the desktop shortcut and then tweak the running program. First, open the desktop shortcut properties sheet and the command line switch Ax to the end of the Target box, where x = the number of instances you need to run (2 for a dual-core, 4 for a quad-core, etc.) Then, launch the program as many times as you need. Finally, in each instance of the program, click Advanced, go to Affinity, and the Specific CPU to run on box, enter 0 for the first core in the first instance and click OK; 1 for the second core in the second instance; and so on. Then you can start your CPU torture tests. http://common.ziffdavisinternet.com/...=189535,00.jpg # When torture-testing the CPU, monitor the temperature with whatever monitoring tool came with your motherboard (e.g. ASUS offers PC Probe II with current boards). If you don't have a monitoring tool, go to the motherboard's manufacturing page, find the downloads for your specific motherboard, and download the utility. # If you overclock too high and the PC won't POST, you have to reset the CMOS. There's usually a switch or a jumper on the motherboard specifically for this purpose. If, for some reason, the switch or jumper doesn't work, or there isn't one at all, power down the PC, unplug it, open the case, and pop out the small, round, disc-shaped battery for about ten minutes. Then, replace it and power back up. The BIOS setup program will be at pure defaults. # Although we purchased a power meter and tested, overclocking doesn't raise the amount of voltage a power supply draws from the wall. The machine with the specs listed above, at idle, drew 119W before overclocking, and drew 120W while overclocked at 10% over spec. Overclocking a CPU First off, let's get this out of the way: There are utilities that allow you to overclock a CPU through a Windows desktop. Ignore them. Many times we have used such a utility, rebooted, and encountered a machine unable to POST. Do your overclocking through the BIOS setup utility. Trust us. There are two ways to overclock some CPUs, but others only offer one way. Extreme-edition Intel Core-2 and Pentium CPUs, and AMD FX CPUs, allow you to tweak the multiplier. All other CPUs require you to tweak the FSB. FSB stands for front-side bus. AMD doesn't have an FSB. We're using FSB as an umbrella term for ease of writing this article. A CPU's frequency is the core frequency of the FSB (before it's multiplied by four, because FSB's are "quad-pumped"), times the CPU multiplier. Thus, a CPU with a multiplier of 8, on a 1333MHz FSB would be a 2.66GHz CPU (1333 / 4 = 333.25 x 8 = 2666, or around 2.66) Note that lots of stuff gets rounded when determining these numbers. If we then raise the multiplier to 10, the CPU's frequency is now 3.33GHz. (333MHz x 10 = 3330MHz or 3.33GUz). That, if stable, is a fairly decent overclock. For the overclock benchmarked earlier, we raised the FSB. Or, if we raise the core FSB frequency from 333MHz to 366MHz (thus raising the quad-pumped core to an effective 1464MHz, and the CPU frequency to 2.96GHz. To sum up, raising either the FSB or the CPU multiplier overclocks the CPU. Most BIOS setup programs allow you to do either. Look for an overclocking interface in the setup program. It should be there somewhere; sometimes it's under Advanced, but often it gets its own heading or page. We can't tell you where it is on your motherboard because there are no standards whatsoever on how a BIOS setup program may be designed. http://common.ziffdavisinternet.com/...=189536,00.jpg Raising CPU and Memory Voltage and Overclocking Memory Sometimes, you actually have to increase the voltage, going to a part in order to successfully overclock it. If you've pushed a component too fast and the PC won't POST, before moving it a step back, raise its voltage ever so slightly. This requires a bit of research, as different CPUs and memory modules have different voltages. Raise voltage sparingly, and only one selection at a time. Too much voltage is one of the rare things that actually can kill a component dead. We make it a rule of thumb never to raise voltage more than 15%; if a component needs more than that for a successful overclock, we're not interested. Overclocking Memory You might inadvertently overclock the memory on a PC just by overclocking the CPU. The memory is usually tied right into the FSB, but some CPUs separate it. This is often referred to "linked" or "unlinked;" If the RAM is tied to the FSB in your motherboard, it's linked; if you can separate them and overclock them separately, you can unlink the RAM. If the RAM will unlink, you should definitely overclock it separately. That way, the memory overclocking won't interfere with the CPU overclocking. If you must overclock the memory via the FSB, you need to balance what the memory and the CPU are capable of together. This doesn't necessarily change anything; just follow the procedure carefully. Overclocking a Graphics Card Overclocking a graphics card is usually a simple matter of wielding two software-based sliders. Unlike memory and CPU overclocking, you can and should overclock graphics cards in Windows (or whatever OS you're running). ATI's graphics card drive interface has ATI Overdrive, the overclocking page, built right in. For Nvidia, you have to download Ntune to grab its overclocking sliders. Since the interfaces are very similar, we're not going to show both. Shown, therefore, is ATI's interface. To overclock the graphics card, simply slide the slider to the right. http://common.ziffdavisinternet.com/...=189537,00.jpg Use the technique described above; except you don't have to reboot. Slide a notch over a little, test, and repeat. That's all there is to it. First tackle the core frequency, find its max, and then find the max you can overclock the memory frequency. Conclusion: Upgrade Your PC for Free Now you know the basic steps to overclocking your CPU, memory, and graphics card. Depending on the motherboard, there might be a lot more about your own computer's BIOS setup program to learn. Some allow you to adjust the very core of the FSB frequency, for example; which throws one more control into the CPU/memory overclocking mess. Others let you delve into the timings of the memory's latencies, but that, technically, isn't overclocking (there's no clock frequency involved, but instead there are wait states to play with). ExtremeTech - Deep technology for enthusiasts and professionals Last edited by xXxexpertxXx; 03-09-2008 at 03:17 AM.