Hardware

Overclocking 101: Speeding up specific processors

Recently, James McPherson introduced you to the background you need before tempting fate. In this Daily Drill Down, he gives you detailed instructions for overclocking specific chips. There's also a reference section to help you look up specs.


Last month, I presented a general outline of how processors are overclocked (see “Overclocking 101: An overview”). In this Daily Drill Down, I’ll help you overclock your specific processor. I’ve included Web sites for reference material and a seven-step procedure to help you successfully put your CPU on steroids.

Processor-specific information
Each processor is different and requires a slightly different process. Below, you’ll find the processor-specific instructions needed to safely overclock a particular type of CPU. Because processor specifications change on a regular basis, I provided links to the manufacturers’ Web sites rather than try to give a complete list of information that will rapidly become obsolete. Remember that you overclock at your own risk. Not only can you fry your CPU, turning it into nothing more than burnt bacon, but manufacturers probably won’t honor the warranty on an overclocked CPU. Overclocking may also void the warranty on your motherboard and add-in cards.

Finally, before you change any specifications, have a look at my overview Daily Drill Down. Then, make sure you read the seven-step procedure for incrementally revving up your chip at the end of this Daily Drill Down. Remember, try before you fry.

Overclocking Intel Celeron processors
The Celeron is Intel’s solution to low-cost PCs. It is available only on a 66-MHz bus and is the easiest Intel processor to overclock. All Intel processors are multiplier-locked, so you simply need to increase the FSB. Because most current motherboards are designed to work with both Celeron’s 66-MHz bus and Pentium II/III’s 100-MHz bus, the overclockable motherboards will be more likely to include multiple PCI/AGP bus multipliers, improving your peripherals’ ability to operate.

Be sure to use PC100 100-MHz memory when overclocking instead of the Celeron-standard PC66 66-MHz memory. PC133 133-MHz memory is available, but it is unlikely that you will be able to get your processor to run at a FSB speed that high. Of course, there really isn’t a big price difference between the two right now, so it might be worth your while to use the faster memory, especially if you might upgrade to a Pentium II or III later.

The Celeron comes in multiple form factors: the now obsolete cartridge for Slot 1 motherboards, a plastic pin grid array (PPGA) for Socket 370, and a flip chip pin grid array (FCPGA), also for the Socket 370. Each format has different technical specifications, but for overclocking the only issue is their varying voltages. To add to the confusion, two different manufacturing processes were used on FCPGA Celerons, increasing the number of voltage options. Consult the documentation that came with your system before making changes. If you don’t have any documentation, your BIOS may inform you of your computer’s current voltage, or you can get Intel’s Processor ID tool from their Web site.

Overclocking Pentium II processors
The Pentium II was the mass-market processor Intel produced for several years. It has been replaced by the Pentium III. Early models (233-333MHz) used a 66-MHz bus, but that was discontinued in favor of a 100-MHz to help distance the Pentium II from the “value” Celeron processor.

As with the Celeron, overclocking a Pentium II is possible only through FSB manipulation. Unfortunately, Pentium II processors have the on-board cache as a separate chip. It was included within the CPU’s cartridge design but was not manufactured with the processor core. This prevents most of these Pentium II processors from overclocking, since their cache memory isn’t capable of operating at the higher speeds.

Overclocking Pentium II processors requires PC133 133-MHz memory to reliably exceed the 100-MHz FSB. While some motherboards support the memory bus offset, using the faster memory will improve overall system performance. You will also need to know your processor’s voltage specifications, but fortunately Pentium IIs are relatively easy to figure out. See the links section at the end of this Daily Drill Down for the location of Intel’s Pentium II datasheets.

Overclocking Pentium III processors
The Pentium III is the fastest offering currently available from Intel and is multiplier-locked like the rest of Intel’s processors. It’s available in both a cartridge format and FCPGA socket 370. Cartridge-based Pentium IIIs at less than or equal to 600MHz sometimes use the same on-die cache format as Pentium IIs and have similar overclocking problems. The FCPGA processors integrate the on-chip cache and are more easily overclocked.

The Pentium III also poses additional hurdles in that some processors use a 133-MHz FSB, requiring high-speed memory or particularly overclock-friendly motherboards. Furthermore, the Pentium III ships with multiple cores, increasing the number of possible voltages. It has apparently been enough of an issue for Intel to create a special Pentium III voltage page on their Web site (see the link section at the end of this Daily Drill Down).

Overclocking AMD Slot A Athlon processors
This is the original Athlon processor released by AMD in a cartridge format physically similar to the one used in Pentium IIs. Also like the Pentium II, it includes the cache on a separate chip, posing the same overclocking limitations.

Unlike Intel’s Pentium II, however, none of these Athlons were shipped with a clock multiplier lock. It took some time for people to understand exactly how the clock multiplier could be adjusted, but eventually someone figured out the engineering interface port on the Athlon and created a fairly simple device that plugs into the Athlon and tells it to change the clock multiplier. These devices go by the nickname “Golden Fingers” and require no special motherboards to utilize. Simply turn the dials or adjust the switches on the Golden Fingers, and your Slot A Athlon will try to run at the new speed. A number of them are readily available online for around $50, and the hardware review sites linked at the end of this Daily Drill Down have reviews of different Golden Fingers.

You will be forced to open the cartridge of the Athlon processor to attach the Golden Fingers. Since you are overclocking, you should be adding a heatsink/fan combination that requires the removal of the Athlon cartridge anyway. Review the section on cooling in “Overclocking 101: An overview,” and you’ll see how easy it is to remove the casing.

Note that this does not overcome the limitations caused by the cache. There is a program called WCPUA, written by H. Oda, that can change the cache divisor, but the program is no longer available on his Web site. He does offer other programs that can help you check your processor’s status and adjust processor cache latencies to squeeze those last ounces of performance from a CPU.

Overclocking AMD Socket A Duron and Athlon processors
These are perhaps the easiest processors to overclock currently on the market. The Duron is a low-cost processor that competes with the Celeron on price but is closer to the Pentium III than the Celeron in performance. The Athlon is a high-performance model that competes directly with the Pentium III on both performance and price.

AMD has locked the multipliers on these processors, but in a rather easily spotted way. Four small bridges labeled “L1” are clearly visible on the surface of the CPU. The speed is set by using a laser to break a particular bridge, making it easy to verify the factory speed of the chip and preventing remarking. Simply reconnecting those four bridges unlocks the processor so that the motherboard can set the multiplier.

This solution requires fine detail soldering, not quite suitable for the average Jill or Joe. Some have used a wiring pen, a $40 device that can draw a thin metal trace. There’s an even better solution, however. Some genius realized that graphite is a conductor. Simply use a number 2 pencil and carefully cover the four pins with a solid layer of graphite, and the processor is unlocked. A 0.5mm mechanical pencil using HB lead is widely considered the easiest way to do this and costs about 35 cents. You can even erase the marks as long as you are careful and use a soft eraser. Figure A shows the L1 bridges circled in red. My drawing is not to scale so that you can more easily see the bridges in question.

Figure A
The disconnected bridges on AMD Duron and Athlon processors can be spanned using a number 2 pencil. This technique unlocks the clock multiplier.


Overclocking outline
Here is the fundamental overclocking procedure, laid out in seven steps. In addition, Table A provides the multipliers commonly used with different bus speeds.

Table A: Component bus multipliers
FSB Speed 66 MHz 100 MHz 133 MHz
Memory** x1 x1 x1
PCI (33 MHz) x1/3
AGP (66 MHz) x1 x2/3 x1/2
**The Memory bus is typically designed to operate at the same speed as the FSB. Some motherboards can run memory faster or slower than the FSB. If the memory is rated to operate at the higher speed, it can improve overall system performance.

Follow these seven steps:
  1. Make sure that your motherboard supports overclocking. (This step is not necessary for Athlon Slot A processors.) I have listed the motherboard features you should look for.
  • Adjustable FSB (required)—1-MHz increments are best.
  • Adjustable voltage (highly recommended)—increments of 0.05 volts are preferred.
  • Adjustable clock multiplier (only on AMD Socket A Duron/Athlon).
  • Adjustable PCI/AGP multiplier (highly recommended)—ability to lock PCI/AGP bus speed preferred.
  • Adjustable memory bus (highly recommended)—ability to lock memory bus speed preferred.
  1. Determine your processor’s default operating parameters (see Table A).
  2. Increase the multiplier (if available) or FSB by one level. Do not increase the FSB if you have the option of increasing the multiplier because the FSB can affect other components on your computer.
  • If you’re increasing the FSB, adjust the PCI/AGP and memory bus ratios (if available). The most feature-rich overclocking motherboards can lock the PCI/AGP and memory buses at their correct speeds.
    1. Test basic stability. The initial test is simply passing the memory test at boot and successfully starting the OS.
    • If the system fails the initial boot sequence, you can consider increasing the voltage. First, increase the voltage to a setting appropriate for your processor at the new speed; this is a fairly safe process. If that fails, consider increasing the voltage outside the normal boundaries, to a maximum of 10 percent above that particular speed’s requirements.
    • If the system remains unable to complete the boot sequence, reduce the FSB/multiplier by one level and try again. Remember to readjust PCI/AGP and memory bus speeds for the new speeds.
    1. Repeat steps 3 and 4 until you determine the maximum bootable speed of the processor.
    2. Test overall system stability. I recommend using a full-system test suite, such as WinBench. Any specific program you require should be run in a fairly stressful way; load the largest and most complex files you have available. Games like Quake 3 and Unreal Tournament are also capable of identifying many overclocking problems when put into demo mode and left running in loops. If you use a game to test for stability, be sure to test the stability of the unmodified machine first to establish a baseline. You should be able to run a game in a loop for at least two hours after a reboot.
    3. If the system does not pass the stability test, reduce the FSB or clock multiplier one level and retest.
    AMD informationIntel informationWinBench Software suite
  • WinBench for Windows 95/98/NT
  • Overclocking links
    In this Daily Drill Down, I’ve shown you how to overclock your specific processor. I’ve included Web sites for your convenience and outlined a seven-step procedure to help you boost your CPU’s performance.
    The authors and editors have taken care in preparation of the content contained herein but make no expressed or implied warranty of any kind and assume no responsibility for errors or omissions. No liability is assumed for any damages. Always have a verified backup before making any changes.

    Editor's Picks