Snappy Chips

Admit it: you're power-mad! No matter how zippy your computer is, you're always looking for ways to squeeze a few extra tracks or plug-in effects out

Admit it: you're power-mad! No matter how zippy your computer is, you're always looking for ways to squeeze a few extra tracks or plug-in effects out of it. You've maxed out your machine's RAM, added a lightning-fast audio drive, and tweaked your OS so it's optimized for audio performance. You've even added a second video monitor so you can open your mix and edit windows side by side, right? (If not, check out “Desktop Musician: Double Vision” in the April 2000 issue.)

In your quest to have the fastest machine on the block, you may have come across the term overclocking, a technique reputed to make your Pentium II run like a Pentium 4 without costing you a dime. No doubt your too-good-to-be-true alarm screamed when you read the breathless tales of miraculous performance gains in various newsgroups. Before you toss overclocking into the urban-legend bin, take a look at the truth behind the hype. Overclocking can buy you some extra megahertz, at little or no cost.

Note, however, that every discussion of overclocking (including this column) begins with a disclaimer such as the following: NOTICE! Overclocking your computer can damage or destroy your hardware, cause erratic behavior (by the computer, not you), scramble data, and aggravate your ulcer. It will almost certainly void your computer's warranty (assuming it lasted longer than the trip home from the computer store). The author and publisher assume no responsibility for any dire consequences arising from your use of the information provided herein. Proceed at your own risk!

Though Intel Celeron chips (see Fig. 1) get the most press when it comes to overclocking, you can also overclock Intel Pentium and AMD Athlon chips. Mac users may be surprised to know that some PowerPC chips are overclockable. We'll take a look at the theory, the techniques, the pitfalls, and the limitations of overclocking. We'll also try to put some perspective on the sort of gains you can achieve.


Overclocking is made possible by a simple fact of chip manufacturing: not all chips in a batch turn out the same. The process of mass-producing a semiconductor with electron pathways only a few atoms wide is understandably precarious, and only the most perfect chips are capable of the highest clock speeds.

According to Intel, only after processors have been assembled and tested can you know their individual capabilities. Otherwise-identical chips are therefore “binned” based on their clock speed.

Overclockers take advantage of this by buying the cheaper, “slower” chips and second-guessing the manufacturer. Whereas a chip maker might err on the side of caution to ensure that a chip doesn't fail in a customer's machine, a determined end-user might be willing to throw caution to the wind for a few more bands of native EQ. The overclocking process at its most basic involves running your own tests for stability as you gradually raise the clock speed.

That's why Intel, AMD, and Apple all officially discourage overclocking. If you run their chips “out of spec,” you're on your own. It's your machine, of course, so do with it as you see fit. Just don't come crying to them if things go badly.

Of greater concern to manufacturers is the nefarious practice of remarking CPUs. Unscrupulous computer makers have been known to overclock a machine without telling the buyer. It's one thing to squeeze your own CPU for extra cycles; it's quite another to get squeezed for the price of an 800 MHz machine when what you get is officially a 700 MHz chip. Unfortunately, some of the steps chip makers have taken to prevent remarking have made life tougher for tweak-head overclockers, too.


The rated speed of a CPU is a function of the speed of the front side bus (FSB) and the clock multiplier. The FSB is the connection between the CPU and the motherboard. Like a digital-audio device, it has a clock that determines the rate at which commands are executed. The faster the rate, the faster the processing.

Modern processors are fast enough that the CPU can run several times faster than the rest of the system; that's the clock multiplier's role. An 800 MHz AMD Athlon processor has an FSB clock speed of 100 MHz and a clock multiplier of 8 (100 MHz × 8 = 800 MHz), for example.


At one time, overclockers adjusted the FSB speed and the multiplier settings until they found a zippy but stable combination. Unfortunately, the multiplier is the most obvious casualty in the war on remarking. Intel took steps first to prevent the clock multiplier from being manipulated; AMD followed suit. As a result, overclockers these days must ordinarily settle for changing only the FSB speed, though aggressive overclockers seem to have found a way to pick AMD's locks. The Mac's multiplier is not locked; in fact, in most cases changing the multiplier is the only way to overclock a Mac.

Not all motherboards allow that sort of manipulation, so overclockers must select their motherboards carefully. Indeed, because the PCI bus gets its clock speed from the FSB, serious overclockers need to choose all of their system components for their ability to get along with nonstandard clock speeds. Interestingly, a whole subcategory, overclocking video cards, has developed, largely to serve the graphics needs of gamers. I've even seen references to overclocking Palm devices.

As anxious as CPU manufacturers are to prevent overclocking, some motherboard manufacturers actually promote their products as being overclocker-friendly. For example, motherboards from ASUS and ABIT (see Fig. 2) allow the end-user to adjust the FSB clock speed in 1 MHz increments for dialing in the best setting. Another boon to overclockers is the ability to set FSB speed directly from the BIOS instead of by manually moving DIP switches on the motherboard.

Of course, Mac users get whatever motherboard Apple decides to use, and Apple is no more interested in making life easier for overclockers than Intel is. As a result, bumping the clock speed on a Mac requires carefully and cautiously resoldering certain jumpers.


The No. 1 risk to overclocked computers is heat. If you've ever looked inside your computer case at that big heat sink with its own dedicated fan on your processor, you already know that CPUs generate a lot of heat. (If you haven't ever looked inside your computer case, please think twice before attempting overclocking!)

The harder you push your CPU, the hotter it gets; melting and burning are possibilities. With proper cooling, however, you can keep the temperature within safe limits. For mild-to-moderate overclocking, you can get away with minor modifications, such as using a specialized CPU cooler and upgrading or adding case fans. It's also worthwhile to check airflow in your computer's interior, bundling cables and maybe even rearranging PCI cards to optimize circulation. The CPU hot-rodder sites (see the sidebar “Hot-Rodders in Cyberspace”) are rife with ads for cooling accessories and related items such as made-to-order cases with multiple fans built in.

At the extreme edge of overclocking, though, such fixes are inadequate, and more drastic measures are required. Lunatic-fringe members trade tales of submerging components in supercooled fluids and building computers in refrigerators. More realistic technophiles generally use a heat-transfer device called a Peltier, which is designed to draw heat away from the CPU to a place where it can be carried away by your fan. That process can cause condensation, though, so you may need insulation to prevent water from shorting out your system.

So how do you measure the temperature of your CPU? On some motherboards, a hardware sensor provides information about the CPU. With a program such as LiveWire Development's Motherboard Monitor 5.1 (MBM), it's possible to track that information as you experiment with higher clock speeds. One such utility for Mac users is Jeremy Kezer's Thermograph 1.3.4.


Now that you've been properly warned and briefed on the theory of overclocking, you may decide to try it for yourself. The sensible strategy is to bump your FSB speed in small increments, testing for stability and temperature, until you find your highest stable speed. However, I'd take some additional precautions before making any changes to my system.

First, back up your system. That's step one in any sort of upgrade, even upgrades that don't risk smoking your CPU. Second, install MBM or some other monitoring package that can tell you how hot your CPU is getting. Third, for anything more than the tiniest changes, upgrade your cooling system. Upgraded heat-sink-and-fan combos are in the $40 range, and Peltiers are available for even less.

Of course, you shouldn't even consider undertaking such an adventure if you have a client coming over or a production deadline looming. Give yourself enough time to mess up and recover before you put your cash flow and reputation at risk.

Now the fun starts. Read your motherboard manual and find out exactly how to change the FSB clock speed. That's typically accomplished on a PC by setting motherboard DIP switches or by changing system BIOS settings. On a Mac it's done by resoldering the jumpers. There may also be a setting to downgrade the memory clock speed so the memory doesn't have to run out of spec, and a similar setting to put the PCI bus back in spec. That's where an overclock-friendly motherboard pays off.

Adjust the FSB clock speed upward slightly. If you're using something like the aforementioned ABIT motherboard with 1 MHz increments, try bumping it no more than a few megahertz; remember that it's being multiplied! Save your settings, restart the computer, and test your new configuration. Having to resolder jumpers to change multiplier settings makes the incremental bump-and-test process much less convenient on a Mac.


You have two main goals in testing your overclocked computer. First, you want to put it under stress to see just how hot the CPU gets. Heat puts the chip at risk, and it can cause data errors. In general, your goal should be to keep the temperature at or near its “stock” level. Your second goal is to be sure the system is stable and reliable. A faster computer that crashes more frequently is hardly a step forward.

There are numerous benchmarking programs available; one that seems to be popular with PC overclockers is SiSoftware's SANDRA (see Fig. 3). SANDRA is available in a freeware version capable of putting your system through its paces while monitoring its behavior, including CPU speed and temperature. Use its CPU benchmarks to keep your system running at or near 100 percent processor usage for an hour or more. If it doesn't crash and the temperature stays within the safety zone, you have a successful overclock. Mac users can turn to Symantec's Norton Utilities or Micromat's TechTool Pro.

If you're greedy, you can go through this process several times until you find the point at which your system no longer works properly. Sometimes additional CPU cooling can stabilize such a system and allow you to get that last megahertz, or you can simply back off to your highest reliable speed. One other high-risk step to consider is raising the voltage to your CPU if your motherboard supports that. It's usually recommended that you raise the voltage a total of no more than 10 to 15 percent, but even small amounts can stabilize the behavior of an overclocked chip.

Before you stake your reputation on your overclocked speed demon, I'd recommend further testing with the music software you use most often. Throw some hefty real-world demands at it, such as tracking as many audio inputs as you expect to need, mixing with as many plug-ins as you can pile on, and applying complex file-based processes such as noise reduction or sample-rate conversion. Remember, the whole point of overclocking is to second-guess the chip manufacturer's tested speed limit, and that means the burden of reliability/stability testing is entirely yours.


Overclocking depends on minor variations in microprocessors, so the performance gains you can expect will vary as well. You may have no luck at all, or you may get a 25 percent increase in processing. Most likely, you'll get a modest gain somewhere in the middle. With processors constantly dropping in price, only you can decide whether overclocking is worth the time, trouble, minor expense, and major risk. It may be hard to make a case for pure “economic” overclocking, but if you simply love tweaking your hardware, it's easier to justify.

If you're thinking of taking the leap, avail yourself of the resources of the online community. Given the “official” stance against overclocking, it's your best source of information on which chips, motherboards, and other components are the best candidates. Online forums and newsgroups are the cyber equivalent of your local Classic Corvette Club, and just the sort of support a chip hot-rodder needs. Just remember: keep it cool.

Brian Smithersis a musician, conductor, and writer in Orlando, Florida. He teaches at Full Sail Real World Education.


This is a partial list — the tip of the iceberg, really — of online resources for overclocking. Keep in mind that all of these groups disavow any responsibility for your melted CPU. So does EM!

Current news on and analysis of PC hardware. Lots of overclocking information, although much of it is more than a year old.

Arguably the granddaddy of hardware sites, with boatloads of reviews and insights into PC hardware issues. One to bookmark even if you're not overclocking.

Dedicated to helping you optimize your PC. It has very active forums and maintains a database of which CPUs and motherboards have been overclocked by users, including what performance gains they achieved.

The name says it all. For PC users.

Although targeted at gamers, a great and timely source of PC system-tweaking information. It also includes information on Palm overclocking.

Lots of good information for Mac users. Think overclocking is a PC thing? A search for “overclock” on this site turned up 353 pages!

At this site, some authorized Mac-hardware guys disseminate unauthorized techniques, like the one that bumps a 400 MHz PowerBook to 500 MHz.

A Japanese site that offers information on a slew of different Mac overclocks, dating back to a Power Mac 4400. This is only for people with refined soldering skills and nerves of steel.

The name says it all. For Mac users.

Home of Motherboard Monitor.

Home of Thermograph.

Home of SANDRA.

The main site for motherboard manufacturer ABIT Computer Corp.

The main site for motherboard manufacturer ASUS Computer International.