MODTHEBOX.COM - Canada's Premier Case Modding Source - Articles - Overclocking 101: Overclocking Fundamentals

I will start off by saying that if you purchased your CPU, AMD or Intel, within the past two years, the multiplier on your CPU has been physically locked. What that means is that while you may have the option to change the multiplier in your BIOS, the CPU will run at that multiplier and that multiplier only. You will not be able to upgrade, or even downgrade, your CPU's multiplier strictly through software adjustments. Microprocessors from Intel based on the Klamath core and any predecessor to it do not have locked multipliers. This will include any Pentium II processor manufactured before August 1998. For AMD processors, the multiplier lock was introduced around July of 2000, with the then new Duron and Thunderbird chips. Intel and AMD both introduced the multiplier lock to address one major problem, and it wasn't computer hobbyists overclocking their machines. Unscrupulous vendors were fraudulently selling overclocked processors as the genuine article, and both companies eventually decided the only way to hamper such activity was to lock the multiplier using circuitry incorporated into the design of the chip.

For the modern Intel owner, unlocking the multiplier is impossible. The chip is physically hardwired with its multiplier, and there are no safe methods available to unlock it. Intel owners are limited to adjusting their FSB to attain higher clock speeds.

AMD owners also have a locked multiplier, but the multiplier lock can be removed. However, modifying your AMD CPU by unlocking your multiplier will automatically void your warranty, so do not take this step unless you are prepared to accept that outcome.

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AMD's Athlon and Duron series chips have a grouping of electrical bridges imprinted on the topside of the chip. They are small gold dots, separated by a laser cut during the manufacturing process. The black marking between the gold dots is the scorch mark from the laser cut. The bridges that control the multiplier lock are found on the top right hand side of the chip, on the bridge labelled L1 (shown above). The L1 bridge is the key to unlocking the multiplier on an AMD chip. Older Duron and Thunderbird chips could be unlocked using the "pencil trick". Take a mechanical pencil, and draw a line from one gold connection to its partner on the opposite side. Repeat the process on the remaining four bridges, and the chip is unlocked. However, on newer designs, the pencil trick doesn't work. Instead, some sort of electrical conduit has to be used to connect the bridges. Some people have used wire and solder to make the connection, others have used conductive grease. The main warning is not to let any connection from one bridge come in contact with any other bridge on the chip. If you have the bridges connected incorrectly and power up the system, it can potentially destroy your processor.

Unlocked L1 bridges

Multiplier:

Above is a picture of a L1 bridge that has been modified using silver conductive grease. You can see how each individual bridge does not touch any other bridge, or the L3 bridge below it. Reinstall the CPU on your motherboard, and you should be able to choose any available multiplier supported by the board. A future article will document and detail unlocking an AMD XP processor.

The benefits of changing your multiplier are that you are only affecting the internal timing of the CPU; your other components will still run stable at the default front side bus speed. With AMD processors specifically, you can generally get a much better overclock employing only multiplier adjustments versus employing only FSB adjustments. The down side to unlocking the multiplier is that the modifications to the chip are intricate, and if not done correctly, can result in serious damage.

Dual adjustment overclock:

Of course, adjusting the FSB and increasing the multiplier are not mutually exclusive overclocking techniques. You can employ both to get a much higher increase in performance. Also, two minor adjustments to the multiplier and FSB will have as big an impact as one major adjustment, and is more likely to be successful. For example, an AMD Athlon 800 MHz could be overclocked to 1.2 GHz by adjusting the FSB from 100 MHz to 150 MHz (8X Multiplier x 150 FSB = 1.2 GHz). Or, it could be overclocked by increasing the multiplier from 8 to 12 (12X multiplier X 100 FSB = 1.2 GHz). However, the likely hood of either of these two configurations being stable without a lot of extra intervention is minimal. Alternately, by adjusting the multiplier to 10 and the FSB to 120 (moderate changes that most systems should handle); the same target of 1.2 GHz can be reached.

Tackling Heat:

The biggest problem with overclocking is heat. The processor is working faster than it was designed to, and the extra overhead translates into heat. Systems tend to become unstable if not cooled properly, CPU's and components that overheat will crash. Be sure that you monitor your CPU and case temps during your burn in tests, and make sure your processor doesn't get too hot. Follow the design specs for your manufacturer. A good rule of thumb is to stay below 70 degrees Celsius. Temperatures higher than that could potentially do irreparable damage to your CPU or motherboard. You may have to invest in a better heat sink and fan, or you may have to provide extra cooling within your case by introducing additional intake and exhaust fans. Case Modding 101: How to Install a Case Fan covers the basics of case fan installation and airflow within your case.

Conclusion:

Early overclocking used to allow users to crank their processor up to the next available processor speed without paying the extra price. But it was a risky business, and overclockable motherboards were far from economical. However, in today's market, reasonably priced components in the hands of educated computer enthusiasts can result in huge overclocks, with systems running at processor speeds not available for months to come. If you decide to embark on this path, it will be guaranteed fun, some frustration, and a better understanding of computer hardware.