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Overclocking
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Overclocking, the black art in the computer world. This is the technique used by many computer hobbyist to make their system runs faster than what they were originally intended. How this is possible: Central processing unit (CPU) is fabricated in discs like silicon called wafers. Each wafer can house from a few tens to hundreds of cpu chips that's made in the same process. The ability of each chips are eventually tested & sorted into different speed categories like 300MHz, 350MHz & 400MHz. Depending on how stringent is the test requirement, some of the 300MHz chips can potentially achieve higher speed say 400MHz under certain conditions. Overclocking is simply to make the 300MHz chip runs at 400MHz by giving it those necessary conditions. These conditions includes a good motherboard that allows the cpu to scale a multitudes of speed while synchronizing with other components in the system, an adequate amount of cooling so that the chip won't fry & in certain cases, a minute adjustment in the voltage supplied to the cpu. The legendary Celeron300A produced by Intel is a living testimony of overclocking. Two of my system are both build with the Celeron300A on Abit motherboards. One of my Slot1 Celeron300A is housed on the Abit BH6 motherboard & it managed to hit 464Mhz. The other Socket370 Celeron300A of mine from Sim Lim Square, Singapore was even more amazing that it hit 504Hz on the Abit BE6 motherboard. Picture of the Slot1 Celeron464 on the AbitBH6 motherboard. Picture of the Socket370 Celeron504 on the AbitBE6 motherboard. So is every cpu overclockable & how to go about overclocking your system? The answer is obviously, No! Not all cpu are overclockable. Depending on how stringent the tests used to classified the chips, the quality of the fabrication process & the way the Front-Side-Bus(FSB) of the chips are configured, certain chips like the Celeron300A is exceptionally easy to overclock. Some, like the Cyrix 686 chips, on the contrary has little potential in overclocking due to its lower yield & quality. The parameters to tweak: FSB & multiplier Your motherboard determines the cpu speed by multiplying the FSB of your system by a multiplier. Eg. the Celeron300A uses a default 66MHz fsb & a multiplier of 4.5 to give 300Mhz. Theoretically, you can force your motherboard to clock your cpu higher by either increasing the fsb or with a higher multiplier. Intel, in its ploy to discourage overclocking, Intel has built a multiplier lock on the newer cpu such that the chips won't work on anything else except the default multiplier. So the only way to overclock these cpu is thus by changing the fsb. Depending on the make of the motherboard, some boards are more stable than others at higher fsb & are thus more overclocking-friendly. Abit is undoubtedly doing a very good job in making these motherboard with its series of BH6, BX6-2, BE6 & BP6 motherboard family for the Intel Slot1 & socket370 cpu with a multitudes of fsb & multiplier to overclock all ranges of Pentium II, Pentium III & Celeron cpu. Note also not all motherboards allow overclocking & some have limited choice of fsb & multiplier that limited its overclocking potential. My first Slot1 Celeron300A was thus overclocked from 300MHz (66Mhz x 4.5) to 464MHz (103MHz x 4.5). This chip does not hit 504MHz (112 x 4.5) probably due to the make of the cpu. My second socket370 Celeron300A was able to hit 504Mhz (112 x 4.5). This is possible probably because that was around the same time where Intel has upgraded it fabrication process quality to start making the Celeron500. Why Celeron300A then? Well the truth is that the earlier batch of 300A to 366 celerons, although probably produced from the same silicon, they were never meant to hit the 500Mhz range. A celeron333 would have required a multiplier of 5 x 66 MHz default settings. So the only possible speed would be 333Mhz(default), 375MHz(5 x 75 MHz), 415MHz(5 X 83), 500(5 x 100 MHz) & so on. If it does not hit 500, it has to settle with a lower 415Mhz. If you work out this way, a 366 requiring a 5.5 multiplier would hit 550 with a fsb of 100 that is closed impossible on the early batches of celerons. It was however reported that some later batches of celeron366 were able to hit the 550 range with additional cooling. The idea is that, the faster the cpu runs, the hotter it gets & the more cooling is required before you fry your brand new cpu. The hotter the chip operates, the faster is the rate of electron migration(engineers will know this) & the shorter is the lifetime of your chip. Why then people still overclock? The truth is that you don't use your PC for more than 3 to 5 years nowadays before the next faster & more advanced chip comes around the corner render your few years old system obsolete. So what is the penalty of being able to use your system for 5 years instead of 10? You figure this out. Why not Pentium II or Pentium III then? The celeron is a strip down version of Pentium II with a lesser amount of on-chip L2-cache. P2 has 512K half-speed L2 cache that comes as two separate die on the slot1 cartridges, depending on the make of these L2 caches, while a very limited few of PII 300 was able to hit 504 with their L2 cache running at 252Mhz(half of 504), most won't make it past even 450. Same goes to P3. By reducing the L2-cache of the celeron from 512k to 128k, Intel managed to squeeze these cache into the celeron chip itself. So if the chips is capable of scaling higher speed, so will the 128K L2 cache that is built on the same silicon. Last but not least, this article serve only as a introduction to overclocking. You are advised to check out other sites like www.tomshardware.com to find out more about tweaking cpu voltages, ways of cooling your overclocked cpu & other details before fiddling with whatever system you have. The author do not assume any responsibility for fried cpu resulting from readers overclocking their system after reading this article. Updated on10/18/99 |