The Hidden Bargain, Overclocking the Pentium III

In the age of rapid obsolescence of computer gear, it is expensive to have a computer that is state of the art. The Leading Edge quickly become the Bleeding Edge because not only is the price differential between a top of the line processor, and the next slowest version out of proportion to the speed differential between the processors, but also because what is state of the art today is obsolete tomorrow.

Fortunately, the informed consumer does not need to go bankrupt, and can still have a processor that is as fast, or faster than the top of the line processors today at a remarkably reduced price. What I am talking about is the hidden bargains available with overclocking.

Before I go any further, I must state that overclocking your processor will void the manufacturers warranty, and it is possible to destroy hardware if you don't know what you are doing. Neither Epinions, nor myself can be held responsible if you do something stupid that requires you to buy new equipment. Before I scare everyone off, it must be stated that if practiced intelligently, overclocking is safe. I have had overclocked systems running for years without a hickup. (In fact, this epinion is being written on a Pentium III 450 running at 632 MHz. See the following link http://www.geocities.com/steve+larrison/IntelOC.jpg )

What kind of savings are available with overclocking? As of 12/26/99, the lowest priced Pentium III 600 (6.0 clock multiplier, 100MHz bus) is $415. You could pay $415 for a Pentium III 600 plus $30 for an average grade CPU fan for a total of $445, or you could buy a Pentium III 450 (4.5 clock multiplier, 100MHz bus) for $201 and a $60 Alpha Cooler and run the thing as fast (using 133MHz bus) as the Pentium III 600 for a total of $261.

You could buy a Coppermine class Pentium III 667 (5.0 clock multiplier, 133MHz bus) for $576 and a average CPU fan for $30 for a total of $606, or you could buy a Pentium III 500E ( 5.0 clock multiplier, 100MHz bus) for $246 plus a $60 Alpha cooler and run the thing as fast (using 133Mhz bus) as the Pentium III 667 for a total of $306. (Note: early reports are that Pentium III 500E's are capable of maxing out the highest bus speed on the Soyo 6BA IV and still being perfectly stable without voltage tweaks. This translates to 776MHz out of a $246 processor, so you do yourself a disservice by running these at 667).

You could buy a Coppermine class Pentium III 733 (5.5 clock multiplier, 133MHz bus) for $769 plus an average CPU fan for $30 for a total of $799, or you could get a Pentium III 550E (5.5 clock multiplier, 100MHz bus) for $388 plus an Alpha cooler for $60 for a total of $448. (Note: people are running 550E's at up to 852MHz )

The key to safe successful overclocking is knowledge. With knowledge, an informed consumer can get incredible performance for a bargin price. Before any discussion of how to overclock is started, it is necessary to understand a few basics about microprocessor production.

When Intel sets out to make some Pentium III's, they don't set out to makea given number of processors at a given clock speed. They will set out to make Katmai class or Coppermine class (see my Pentium III Explained epinion for an explanation) processors. Physically, a Katmai class Pentium III 450, 500, 533, 550, and 600 are identical. It makes no difference what the clock speed is, the processors are identical. The difference between a Pentium III 450 and a Pentium III 600 or 600B is related to firmware controlling the processor.

Since there is no difference in the components of any speed Katmai class processor from any other Katmai class processor, (Same holds true for Coppermines) Intel uses a process called speed binning to sort out various processors. Internal testing determines that the highest performing processors get the highest speed grade. (There is variation in all manufacturing processes, not just the process for making PC microprocessors ) Lower performing processors get lower speed grades.

Opportunities for the informed consumer arise because in addition to raw performance capability of a processor, another variable comes into demand for determining what speed to rate a processor at - market demand. There is an incredible price difference between the top of the line of a given class processor, and the bottom of the line of that same processor. Although Intel would love to sell all of their processors at the maximum performance possible, market demand simply doesn't support this because of the price elasticity of demand. Therefore, Intel will frequenty speed rate their processors at a speed much lower than what the processor is capable of performing at. (Remember, the components in all Katmai class processors are the same as all other Katmais, the components in all Coppermine class processors are the same as all other Coppermines )

There are 2 variables involved in determining clock speed of a processor -bus speed, and clock multiplier. A Pentium III 450 uses a 100MHz bus speed, and a 4.5x clock multiplier. A Pentium III 600 uses a 100MHz bus speed, and a 6.0x clock multiplier. A Pentium III 600B uses a 133MHz bus speed, and a 4.5x clock multiplier. As you have probably figured out by now, CLOCK SPEED = BUS SPEED x CLOCK MULTIPLIER.

This is where things get interesting. Although the clock multiplier is set in firmware, and there are no known ways for the average consumer to change their clock multiplier since it is control by Intel (who has a vested interest in getting full price for full performance), the bus speed is controlled by the manufacturer of the motherboard.

Although notoriously stable, Intel motherboards obviously are not the best overclocker motherboards. But the free market and capitalism being what they are, there are several motherboard manufacturers that not only allow you to overclock, they really encourage it. The 3 motherboards I would recommend most to any overclocker are the ABIT BE6 rev 2 ( or really any generation of ABIT since their original BX board the BX6 ), the Asus P3B ( first generation of Asus motherboard with bios controllable bus speed and voltage settings. Although older Asus motherboards allow overclocking, bus speed control is done via jumper settings on the motherboard. These are significantly more difficult than a soft menu type control of bus speed. Also, older Asus motherboards do not allow voltage tweaking, but more on that later.), or the Soyo 6BA IV ( excellent, stable, high performance motherboard ) Note: These are not the only brands of motherboards that support overclocking, just 3 of the best. I have used Aopen before, but rate it lower because of the lack of voltage control.

To overclock, you simply need to hop into the BIOS of any of these motherboards (hit DEL during bootup) and change the bus speed. Since CLOCK SPEED = CLOCK MULTIPLIER x BUS SPEED, running the bus speed higher than the stock 100MHz or 133MHz will increase the operating speed of the processor, and entire system as well.

I mentioned earlier the voltage tweakability of motherboards as an important criteria of motherboard selection. Voltage tweaking is an old overclocker trick to increase stability at a given speed. Simply put, there are times when a system will operate and a given speed, but not be entirely stable at that speed. Upping the voltage supplied to the processor a little bit (10% or less, or you run a serious risk of destroying your processor) increases stability. Before you freak out too much on this advice, it should be noted that Intel has "borrowed" this overclocker trick in the past. The stock core voltage for Katmai class Pentium III processors is 2.0 volts except for the Pentium III 600. The Pentium III 600 uses a 2.05 volt core. This tells me that when the Pentium III 600 was first released, Intels process capability required the voltage tweak (2.5%) to get stability. As process capability improved, this requirement went away. I can run the Pentium III 450 in this machine at 600MHz with 1.7 volts. When I run at 632 MHz, I use stock 2.0 voltage. (Note: Stock voltage for Coppermine processors is 1.6v )

Aside from having knowledge of component selection (quality motherboard, quality RAM, ... ), system cooling is another important area of overclocking success (especially at higher speeds like the 40% overclock I am running right now ). A review on cooling will be reserved for a separate epinion.

Note: For Katmai class Pentium III's, the Pentium III 450 is the chip of choice, for Coppermine class Pentium III's current conventional wisdom says go with processors that run a native 100MHz bus. The sweet spot (clock multiplier) for overclocking Coppermines has not been determined yet.