CPU undervolting and battery life observations

I"ve had some spare time recently and decided to start swapping out cpu's in my W5F to see where better battery life could be had, I was quite suprised at what i found.

Using an Asus W5F with the screen brightness @ lowest all devices enabled idling in windows

T7200 .095V @ 1ghz, according to NHC i was at 13.5-14.2 W/H (Watts/H)

T1200 .095V @ 1ghz 10.3-11.1 W/H

T2500 .095V @ 1ghz 8.8-9.5 W/H

The core solo I have runs @ 0.95v @ its full speed of 1.5ghz and it doesn't use that much more power either at that speed but you can still tell its a single core cpu performance wise.

What i noticed is that the T2500 gave the best battery life (and performance) relative to the core solo. The T7200 was by far the most power hungry.

Heres what i'm thinking, the T7200 has 2mb more cache(4mb) and obviously that is going to take more power thats a given. With the T1200 working I noticed while @ 1ghz its usage was quite high when browsing the net and doing other tasks.

I couldn't tell a difference in performance with the T2500 or T7200 @ 1ghz but the T2500 was much more power effcient and gave great performance.

Now my testing methods arn't the most scientific however they were repeated in the same situation multiple times.

Now what I think i'm going to do is grab a T2060 or 2080, (533fsb and 1mb of cache) and see if that is even more power efficient than the T2500 i'm using right now.

 

hey, if you dont want that T7200, I will trade you my T5300 @1.73, 533Mhz 2mb for it, plus something to make up the difference in costs.

K-TRON

 

I"ll have to let you know about the cpu, i'm kind of in limbo as to whether or not i'm going to sell this notebook, been kinda holding out for the mxm3 8800 cards to get released. The T7200 i have in it now can run @ 2ghz @ 1.05v a nice undervolt.

 

I've had a feeling that the bigger cache would leak more power.

Your findings tend to support this.

John

 

John you have said that many times. Looks like you may have been on to something, good job.

 

are those idling or load numbers?
it could be different under load.. just a thought.

 

Those results were idling, The following results were made with screen brightness @ max for all runs and using orthos as the cpu stress program:

Core Solo T1200 (1.5ghz) Running 1.5ghz @ .95V


Core solo Running @ 1ghz @ 0.95v


Core Duo T2500 @ 1ghz 0.95v


Core Duo T2500 @ 2ghz 1.125v


As you can see with the Core solo undervolted 0.95v there isn't alot of difference at load between 1.5ghz and 1ghz.

The T2500 is a bit more power hungry @ 1ghz and .95v under load and as expected significantly more so @ 2.0ghz

IIRC the T7200 was around 34W/H while under load @2ghz (1.05v) in orthos (forgot to take a screen shot) If i get bored I may swap the T7200 back in later, its currently in my Z84j so its a bit of work to swap them out.

Keep in mind with these results is that all the cpu's involved were undervolted and tested in a very power efficient notebook. Hopefully these results can help others better understand the different power requirements for the respective cpu's

 

mm thank you very much for doing the test, that was precisely why i asked for load. I just ordered a t60p with a t2700 in it instead of a t7600 that my friend has. He can get down to 10 watts in usage so i was wondering if i would get more or less than him with this other proc.

 

IF your friend can get 10w/h with a T60p I'd be very impressed as I couldn't get anywhere close to that with my W5F and i only have a 12" screen.

Performance wise the 2700 will be behind the 7600 for sure, but depending on your use it probably won't be that noticeable. One thing about the T7200/7400/7600's is that they won't scale back the fsb while on battery. I remember reading an Anandtech artivle stating the new Santa Rosa notebooks based on the new C2D's getting better battery life becasue of that. Good luck with your t60p.....What are you doing with your V6J?

 

10W power drain on a T60p is good. It must be aggressive in cutting power to peripheral components and throttling back the GPU.

I could get the Samsung Q35 (12.1",T5600 + Intel 945GM) down to about 9W with a fairly dim display while my Zepto 6024W (14.1", T7300 + 965GM) struggles to get below 15W. The Sony G11 (12.1" LED backlight, U1500 + Intel 945GMS) can get below 6W, but it's a notebook designed for power efficiency, not performance.

John