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.

Intel Processor Power Requirements
SpeedStd VoltageMax VoltageTypical PowerMax Power
P54C (Pentium)
75MHz3.3V3.6V3.00W8.00W
90MHz3.3V3.6V3.50W9.00W
100MHz3.3V3.6V3.90W10.10W
120MHz3.3V3.6V5.06W12.81W
133MHz3.3V3.6V4.30W11.20W
150MHz3.3V3.6V4.90W11.60W
166MHz3.5V3.6V5.40W14.50W
200MHz3.5V3.6V6.50W15.50W
P55C (Pentium w/MMX)
166MHz2.8V2.9V6.10W13.10W
200MHz2.8V2.9V7.30W15.70W
233MHz2.8V2.9V7.90W17.00W
P6 (Pentium Pro)
150MHz (256K)3.1V3.3V23.00W29.20W
166MHz (512K)3.3V3.45V27.50W35.00W
180MHz (256K)3.3V3.45V24.80W31.70W
200MHz (256k)3.3V3.45V27.30W35.00W
200MHz (512k)3.3V3.45V32.60W37.90W
200MHz (1MB)3.3V3.45V43.00W47.00W
Pentium II
233MHz2.8V2.9V33.60W34.80W
266MHz2.8V2.9V37.00W38.20W
266MHz (65x core)2.0V2.1C17.80W19.50W
300MHz2.8V2.9V41.40W43.0W
333MHz2.0V2.1V21.80W23.70W
350MHz2.0V2.1V20.80W21.50W
400MHz2.0V2.1V23.60W24.30W
450MHz2.0V2.1V26.40W27.10W
Celeron
266MHz2.0V2.1V?16.59W
300MHz2.0V2.1V?18.48W
300MHz (300A)2.0V2.1V?19.05W
333MHz2.0V2.1V?20.94W
Xeon
400MHz (512K)2.0V2.1V?30.80W
400MHz (1MB)2.0V2.1V?38.10W
450MHz (512K)2.0V2.1V?34.50W

AMD Processor Power Requirements
SpeedStd VoltageMax VoltageTypical PowerMax Power
K5
PR75 (75MHz)3.52V3.6V9.50W11.88W
PR90 (90MHz)3.52V3.6V11.40W14.25W
PR100 (100MHz)3.52V3.6V12.67W15.84W
PR120 (90Mhz)3.3V3.6V8.91W12.64W
PR133 (100MHz)3.3V3.6V9.90W14.04W
PR166 (116.7MHz)3.3V3.6V11.55W16.38W
K6
166MHz2.9V3.0V10.30W18.75W
200MHz2.9V3.0V12.00W22.50W
233MHz3.2V3.3V17.20W31.35W
266MHz2.2V2.5V8.75W14.55W
300MHz2.2V2.5V9.75W15.40W
K6-2
266MHz2.22.5V8.85W14.70W
300MHz2.22.5V10.35W17.20W
333MHz2.22.5V11.40W19.00W
350MHz2.22.5V11.98W19.95W
380MHz????
400MHz????

Cyrix Processor Power Requirements
SpeedStd VoltageMax VoltageTypical PowerMax Power
6×86
PR90+ (80MHz)3.3V3.6V12.87W16.92W
PR120+ (100MHz)3.3V3.6V14.85W19.44W
PR133+ (110MHz)3.3V3.6V15.84W20.88W
PR150+ (120MHz)3.3V3.6V16.83W21.96W
PR166+ (133MHz)3.3V3.6V18.15W23.76W
PR200+ (150MHz)3.52V3.6V20.77W25.20W
6x86L
PR120+ (100MHz)2.8V2.9V11.13W13.83W
PR133+ (110MHz)2.8V2.9V11.71W14.73W
PR150+ (120MHz)2.8V2.9V12.56W15.60W
PR166+ (133MHz)2.8V2.9V13.41W16.50W
PR200+ (150MHz)2.8V2.9V14.28W17.69W
6x86MX
PR166 (133MHz)2.9V3.0V10.10W16.70W
PR166 (150MHz)2.9V3.0V10.70W17.70W
PR200 (166MHz)2.9V3.0V11.50W19.10W
PR233 (188MHz)2.9V3.0V13.10W21.70W
PR266 (208MHz)2.9V3.0V13.80W23.00W
M II
PR300 (225MHz)2.9V3.0V15.00W24.90W
PR300 (233MHz)2.9V3.0V15.40W25.50W
PR333 (250MHz)2.9V3.0V16.60W27.60W
PR350 (300MHz)2.9V3.0V??
PR350 (300MHz)2.9V3.0V??

IDT Processor Power Requirements
SpeedStd VoltageMax VoltageTypical PowerMax Power
C6 (Winchip)
180MHz3.52V3.6V?11.50W
200MHz3.52V3.6V?13.00W
225MHz3.52V3.6V?14.80W
240MHz3.52V3.6V?15.80W
Winchip-2
200MHz3.52V3.6V?12.00W
225MHz3.52V3.6V?13.00W
240MHz3.52V3.6V?14.00W
250Mhz3.52V3.6V?15.00W
266MHz3.52V3.6V?16.00W


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