My Dell Inspiron 8600 is wrapping up it's 4th(!) year of service as I type this, and just a few weeks ago I found some excellent free software tools to improve its battery life, lower operating temperatures and quiet the cooling fans down. Since I am a reasonably well read computer enthusiast, and I only found these programs recently, I thought it might be fair to guess not too many people are aware of them.
introduced me to Notebook Hardware Control
, and I forget where I learned about Dell Inspiron Inspiron/Latitude/Precision fan control
. I didn't write these programs, nor am I the first to use them, but I did some minimally scientific tests using them, and made some charts in Excel, so I thought I'd share the results.
Dell Inspiron 8600
Pentium M 1.4GHz, Banias
1.25 GB DDR
The first thing I wanted to try was lowering the CPU voltage. Since this option was unavailable in the BIOS, and since Dell (AFAIK) hasn't released any tools for doing this, I thought it wasn't possible. With NHC, it is VERY possible.
Just run NHC, and check under the "CPU Voltage" tab.
The Pentium M can (as most of you know) Speed Step. This chip runs at 1.4 GHz when loaded, and 600 MHz at idle. The Dell factory voltages were:
1400 MHz - 1.484 V
600 MHz - 0.940 V
Using CPU Burn-in
I ran the core at maximum load for 20 minutes and marked the final temperature reported by the Fan Control program. Then I lowered the voltage, and repeated. Results are shown below:
As you can see, the notebook ran fine all the way down 1.052 V. Any lower and Windows froze up intermittently. This is 70% of the stock voltage! I was suprised myself. The temperatures also dropped significantly.
The blue line indicates relative power usage by the CPU, calculated as,
where this article
and others suggest CPU power usage is proportional to voltage squared. So the final result shows that CPU power usage is nearly halved by using the new core voltage!
Using my handy Kill-A-Watt,
I measured my total power usage. The laptop was plugged in, the screen was set to full brightness and CPU Burn-in was used again.
For reference turning the display off resulted in -10 W used, and turning the display from maximum brightness to minimum brightness reduced energy usage by 5 W.
So in conclusion, I now use NHC to set the CPU voltages as specified above, and Dell fan control to leave the fan off when CPU temp is below 55ÂºC. When heavy processing is happening, the core will heat up to 55ÂºC then the fan kicks on low, and the core cools down in a minute or two back to 45ÂºC. These setting result in much quieter and cooler computing than before. I haven't tried to run any battery lift tests, but it seems like the battery run-time must be significantly improved by the new voltage settings.
I hope this report is helpful and encourages someone else to try these two programs!