Power Calculation Empirical Formula for UNDERVOLTERS

In the hope that it will help some UnderVolters, I deduced following formula for approximate value. By no means it is scientific, rather empirical formula based on lot of info from the web.

The Power requirement change at reduced voltage is not entirely proportional to the voltage drop, rather it drops in exponential way. The ratio of voltage drop vs Power Drop is not directly propertional either(not a fixed multiplication), hence this formula is deduced to help.

The Formula for Calculation of Approximate Undervolt Wattage for the Rated Speed( Assuming Speed is constant).

RV= Rated Voltage ( Rated Voltage for the CPU)
UV= Under Voltage (current Voltage set to CPU)
RW= Rated Wattage at Rated Voltage
UW= Under Volt Wattage

UW=RW * (UV/RV) * ( 1 - ( (RV - UV)/ RV))

This formula has been deduced after doing research around, and comparing the formula values to the Old Radiate software.

For reference I used this site
http://www.silentpcreview.com/article37-page1.html

as well as some other sites, and also used tested the values againt Radiate software.

These are some values obtained from Radiate and compared against:

AMD MP
1800 1.9v 96.7w
1800 1.8v 86.8w Prorated Wattage: 91.6105 Ratio Actual/Prorated: 0.9474
1800 1.7v 77.4w Prorated Wattage: 86.5210 Ratio Actual/Prorated: 0.8945
1800 1.6v 68.6w Prorated Wattage: 81.4315 Ratio Actual/Prorated: 0.8424
1800 1.5v 60.2w Prorated Wattage: 76.3421 Ratio Actual/Prorated: 0.7885


AMD ATHLON
1200 1.9v 90.2w
1200 1.8v 81.0w Prorated Wattage:85.4526 Ratio Actual/Prorated:0.9478
1200 1.7v 72.3w Prorated Wattage:80.7052 Ratio Actual/Prorated:0.8958
1200 1.6v 64.0w Prorated Wattage:75.9578 Ratio Actual/Prorated:0.8425
1200 1.5v 56.3w Prorated Wattage:71.2105 Ratio Actual/Prorated:0.7906

1000 1.9v 75.1W Prorated Wattage: 59.2894
1000 1.5V 46.8W Ratio of Prorated Wattage vs Actual Wattage: 0.7893

P4
2000 1.8v 108.8W
2000 1.5v 75.6w Prorated Wattage:90.6666 Ratio Actual/Prorated:0.8338

P4 XEON

2000 1.8v 88.5W
2000 1.7v 78.9W Prorated Wattage:83.5833 Ratio Actual/Prorated:0.9439
2000 1.6v 69.9W Prorated Wattage:78.6666 Ratio Actual/Prorated:0.8885
2000 1.5v 61.5W Prorated Wattage:73.7500 Ratio Actual/Prorated:0.8338


It is obvious we will get most benifit out of UNDERVOLTing at full load when the CPU is running at it MAX speed(Full speed).

For Example in this thread
http://forum.notebookreview.com/showthread.php?t=20249

blksnake did an excellent posting with verygood results.
I think he is defintely lucky to have nice chip.

In his case the voltage drop at Full speed is from 1.45v to 1.175V.

As per the spec the rated wattage for ML-34 is 34watts(it is just a coincidence that both ML-34 last two digits and 34watts match!) For ML-37 it is 35 watts.

Let us see how much he might be saving:

Final Wattage= 34 * (1.175/1.45) * ( 1 - ( (1.45 - 1.175)/ 1.45))

Final wattage is 22.32watts approx 22.5 watts. So from 34 t 22.5 watts!? suprise isn't it. Saved 11+ watts of Power!!?

No, wonder he dropped 11 C in temp at full speed under full load. Not only he dropped 11 C, but his battery life at full load may increase as much as 30 min with standard battery.


What about the low speed at 800Mhz. at 0.9 volts
At that speed Rated voltage is 1.0v and Rated Wattage is 7.9w.

Calculated wattage is 6.4 watts at 0.9 volts. So he only saved 1.5 watts. Not bad, when every watt is counted.

But all these figures are at full load for that stepping.
At 800Mhz at 20% load it may not consume more than 4 watts approx.

I am doing some more research on power consumption numbers for each component. Probably I will compile all those some time later.

I did not know until now power consumption for 14" LCD can vary as much as 4-5 watts from lowest brightness to Highest(Typical min is 2 watts Max around 7 watts)!! And an active running wireless can consume as much as 3 watts?

Please correct me if I said any thing wrong, and please add your valueble comments.

I started this research after ordering my Compaq V2000Z with ML-37, and found this forum really helpful. Thought my research may be helpful to someone.

 

Gee man, good work!
We saw in various threads now that the Turion takes easily undervolting with great results. You say 30 more min with standard battery. Does this mean 6 cell battery? If yes, what abou the battery wear level. In another thread people reported unusually high wear levels of the 6 cell battery with v2000z, which hinted at either bios or battery problems.

 

I mistook blksnake UNDERVOLT voltage at full speed as 1.1v instead of 1.175v . Now it is corrected and values changed accordingly. Sorry :-<

 

I mean standard battery, but at full load. At full load standard battery is not going to last more 1:30 min. For example running some encoding. In this scenario, Undervolting to 1.175 may add upto 20-30 min.