# CPU Power Requirements

### Who Needs the Power

These charts show the ‘Typical’ and ‘Maximum’ power dissipation at spec for all current Pentium class processors. Most of these numbers were taken directly from the data sheets, however in a few cases the values had to be calculated. Note that each manufacturer calculates maximum power dissipation in a slightly different manner. For Cyrix, the maximum is calculated using the maximum ‘safe’ voltage multiplied by the current draw when the processor is 100% utilized. For other manufacturers, the maximum power is calculated by using the highest recommended voltage (which may or may not be less than the maximum ‘safe’ voltage) time the current draw when the processor is 100% utilized. All manufacturers calculate the ‘Typical’ power by using the recommended processor voltage multiplied by the current draw under a ‘normal’ load (somewhat less than 100% CPU utilization).

For overclockers, this chart can also be used to estimate the power dissipation for various MHz and voltages. This is done by calculating the current draw for Typical and Maximum power draw (at the Standard Voltage or at Max Voltage, depending if a Cyrix processor or not), then dividing that by the rated MHz. Next, multiply the amps per MHz by the overclocked speed and then multiply by the voltage. This will be your estimated Typical and Estimated power dissipation.

For example, a Cyrix M II 300 running at 300MHz would be calculated as follows: Typical current = 15W / 2.9V = 5.17A and Max current = 24W / 3.0V = 8A. Now we calculate the amps per MHz as follows: 5.17A / 225MHz = .023A abd 8A / 225MHz = .035A (approx). Now we calculate the current at 350MHz like this: .023A * 300MHz = 6.9A and .035A * 300MHz = 10.5A. Finally, we calculate the power dissipation as: 6.9A * 2.9V = 20.01W (Typical) and 10.5A * 3.0V = 30.45W (Max). If the voltage were increased above 3.0V to get the chip working stably, that would need to be figured in as well.

Another example is the Intel Celeron 300A at 450MHz. In this case only the Max Power was provided in the data sheets, so this is what we will use. 19.05W / 2.0V = 9.53A. 9.53A / 300MHz = .032A/MHz. 450MHz * .032A = 14.4A. 14.4A * 2.0V = 28.8W. If the voltage is increased to 2.3V for ‘stability’, the power dissipation becomes 33.13W. One thing to note here is that motherboards begin to have problems when the current exceeds 10A, so while overclocking this much may not be a problem for the processor (in the case of the Celeron 300A), the motherboard may not be able to handle the current draw.

Note that these numbers are only estimates, because the current draw typically becomes slightly less as the MHz increases. Using these calculations will, however, allow you to make sure that your motherboard can handle the maximum load you are trying to throw at it.

 Speed Std Voltage Max Voltage Typical Power Max Power P54C (Pentium) 75MHz 3.3V 3.6V 3.00W 8.00W 90MHz 3.3V 3.6V 3.50W 9.00W 100MHz 3.3V 3.6V 3.90W 10.10W 120MHz 3.3V 3.6V 5.06W 12.81W 133MHz 3.3V 3.6V 4.30W 11.20W 150MHz 3.3V 3.6V 4.90W 11.60W 166MHz 3.5V 3.6V 5.40W 14.50W 200MHz 3.5V 3.6V 6.50W 15.50W P55C (Pentium w/MMX) 166MHz 2.8V 2.9V 6.10W 13.10W 200MHz 2.8V 2.9V 7.30W 15.70W 233MHz 2.8V 2.9V 7.90W 17.00W P6 (Pentium Pro) 150MHz (256K) 3.1V 3.3V 23.00W 29.20W 166MHz (512K) 3.3V 3.45V 27.50W 35.00W 180MHz (256K) 3.3V 3.45V 24.80W 31.70W 200MHz (256k) 3.3V 3.45V 27.30W 35.00W 200MHz (512k) 3.3V 3.45V 32.60W 37.90W 200MHz (1MB) 3.3V 3.45V 43.00W 47.00W Pentium II 233MHz 2.8V 2.9V 33.60W 34.80W 266MHz 2.8V 2.9V 37.00W 38.20W 266MHz (65x core) 2.0V 2.1C 17.80W 19.50W 300MHz 2.8V 2.9V 41.40W 43.0W 333MHz 2.0V 2.1V 21.80W 23.70W 350MHz 2.0V 2.1V 20.80W 21.50W 400MHz 2.0V 2.1V 23.60W 24.30W 450MHz 2.0V 2.1V 26.40W 27.10W Celeron 266MHz 2.0V 2.1V ? 16.59W 300MHz 2.0V 2.1V ? 18.48W 300MHz (300A) 2.0V 2.1V ? 19.05W 333MHz 2.0V 2.1V ? 20.94W Xeon 400MHz (512K) 2.0V 2.1V ? 30.80W 400MHz (1MB) 2.0V 2.1V ? 38.10W 450MHz (512K) 2.0V 2.1V ? 34.50W

 Speed Std Voltage Max Voltage Typical Power Max Power K5 PR75 (75MHz) 3.52V 3.6V 9.50W 11.88W PR90 (90MHz) 3.52V 3.6V 11.40W 14.25W PR100 (100MHz) 3.52V 3.6V 12.67W 15.84W PR120 (90Mhz) 3.3V 3.6V 8.91W 12.64W PR133 (100MHz) 3.3V 3.6V 9.90W 14.04W PR166 (116.7MHz) 3.3V 3.6V 11.55W 16.38W K6 166MHz 2.9V 3.0V 10.30W 18.75W 200MHz 2.9V 3.0V 12.00W 22.50W 233MHz 3.2V 3.3V 17.20W 31.35W 266MHz 2.2V 2.5V 8.75W 14.55W 300MHz 2.2V 2.5V 9.75W 15.40W K6-2 266MHz 2.2 2.5V 8.85W 14.70W 300MHz 2.2 2.5V 10.35W 17.20W 333MHz 2.2 2.5V 11.40W 19.00W 350MHz 2.2 2.5V 11.98W 19.95W 380MHz ? ? ? ? 400MHz ? ? ? ?

 Speed Std Voltage Max Voltage Typical Power Max Power 6×86 PR90+ (80MHz) 3.3V 3.6V 12.87W 16.92W PR120+ (100MHz) 3.3V 3.6V 14.85W 19.44W PR133+ (110MHz) 3.3V 3.6V 15.84W 20.88W PR150+ (120MHz) 3.3V 3.6V 16.83W 21.96W PR166+ (133MHz) 3.3V 3.6V 18.15W 23.76W PR200+ (150MHz) 3.52V 3.6V 20.77W 25.20W 6x86L PR120+ (100MHz) 2.8V 2.9V 11.13W 13.83W PR133+ (110MHz) 2.8V 2.9V 11.71W 14.73W PR150+ (120MHz) 2.8V 2.9V 12.56W 15.60W PR166+ (133MHz) 2.8V 2.9V 13.41W 16.50W PR200+ (150MHz) 2.8V 2.9V 14.28W 17.69W 6x86MX PR166 (133MHz) 2.9V 3.0V 10.10W 16.70W PR166 (150MHz) 2.9V 3.0V 10.70W 17.70W PR200 (166MHz) 2.9V 3.0V 11.50W 19.10W PR233 (188MHz) 2.9V 3.0V 13.10W 21.70W PR266 (208MHz) 2.9V 3.0V 13.80W 23.00W M II PR300 (225MHz) 2.9V 3.0V 15.00W 24.90W PR300 (233MHz) 2.9V 3.0V 15.40W 25.50W PR333 (250MHz) 2.9V 3.0V 16.60W 27.60W PR350 (300MHz) 2.9V 3.0V ? ? PR350 (300MHz) 2.9V 3.0V ? ?

 Speed Std Voltage Max Voltage Typical Power Max Power C6 (Winchip) 180MHz 3.52V 3.6V ? 11.50W 200MHz 3.52V 3.6V ? 13.00W 225MHz 3.52V 3.6V ? 14.80W 240MHz 3.52V 3.6V ? 15.80W Winchip-2 200MHz 3.52V 3.6V ? 12.00W 225MHz 3.52V 3.6V ? 13.00W 240MHz 3.52V 3.6V ? 14.00W 250Mhz 3.52V 3.6V ? 15.00W 266MHz 3.52V 3.6V ? 16.00W