Optimal Speed for Your CPU

Overclocking PII
Overclocking Basics of CPU
Setting CPU speed

Memory market Memory guide

Optimal Speed for Your CPU
Remember, just because your neighbor or brother or whoever can achieve a certain speed with their identical CPU doesn't mean that yours should be able to hit that same level. Each and every CPU is unique. Considering these small cores have 8 million trace routes, it should come as no surprise that no two CPU cores behave the same under stress.

In addition, the Level 2 cache, which operates at approximately one half the speed of the CPU, is matched by Intel to the speed of the CPU core to which it is connected. There's usually a good deal of leeway, but the individual speed of your cache is a key limiting factor in overclocking your CPU.

The goal of overclocking is to find your CPU's comfort zone--the speed at which it will run reliably, without system errors or data corruption. Here are some common, relatively conservative settings.

Pentium IIs With Default 66 MHz FSB (233 MHz to 333 MHz)
233-MHz and 266-MHz Pentium IIs

Overclocked Speed Clock Multiplier FSB Speed Chipset
300 MHz 4.0 75 MHz 440LX
300 MHz 3.0 100 MHz 440BX
336 MHz 3.0 112 MHz 440BX

300-MHz Pentium II

Overclocked Speed Clock Multiplier FSB Speed Chipset
338 MHz 4.5 75 MHz 440LX
350 MHz 3.5 100 MHz 440BX
392 MHz 3.5 112 MHz 440BX
400 MHz 4.0 100 MHz 440BX

333-MHz Pentium II

Overclocked Speed Clock Multiplier FSB Speed Chipset
350 MHz 3.5 100 MHz 440BX
375 MHz 5.0 75 MHz 440BX
392 MHz 3.5 112 MHz 440BX
400 MHz 4.0 100 MHz 440BX

Note: To run reliably at a 100-MHz FSB, you need to have 100-MHz SDRAM installed in your system. Also note that in many of the cases listed above, increasing the FSB speed requires you to lower the clock multiplier on your system.

Pentium IIs With Default 100-MHz FSB (350 MHz to 450 MHz)
Since August 1998, Intel has been locking the clock multiplier on its CPUs, so it probably will not be possible to change the multiplier when overclocking a 350-MHz, 400-MHz, or 450-MHz Pentium II. If you try, the CPU will either refuse to boot the machine, or it will boot it up at 1/3 its proper speed. To get around this limitation, a Pentium II overclocker's only remaining option is to increase the speed of the frontside bus.

Default Clock Speed Default Clock Multiplier Overclocked
FSB Speed
CPU Speed
350 MHz 3.5x 112 MHz 392 MHz
400 MHz 4x 112 MHz 448 MHz
450 MHz 4.5x 112 MHz 504 MHz

Danger of Increasing FSB Speed
Increasing the speed of the FSB also increases the speed of the PCI and AGP buses so errors might result from some older components refusing to run properly at the higher bus speeds. For instance, overclocking from 100-MHz FSB to 112 MHz results in the PCI bus being overclocked to 37 MHz (instead of 33 MHz), and the AGP bus being overclocked to 74 MHz (instead of 66 MHz). Because newer PCI and AGP cards are being designed with greater tolerances, however, this is becoming less of a problem.

Setting the CPU speed