OK had some time to crunch numbers and respond to Hundred gunner in a more thoughtful mature manner than my bad attempt at fun.

Travelstar™ 7K320 and Travelstar™ 5K320 both are SATA 3.0. 7K

link, 5K

link. These are links to the technical document where I obtained my power usage information.

Start up is 5.5w vs 5.0w (7200 vs 5400); seek both are 2.2w, read/write both 1.8w, performance idle both 1.7w, active idle 1.0w vs 0.8w, stand by and sleep are the same.

OK to Hundred gunner you talk of your and your friends rigs? Are they the same? Brand, component, drivers OS other than HDD? If not, of no use in any kind of real comparison. If same or similar components but not the same notebook once again of no use. If the same in all ways other than HDD battery must be tested to confirm same state of wear same ability to hold charge. Do you meet this final criteria? If not let me just throw some information to get all to consider.

The anecdotal premise thrown out is 7200 has a 10% to 15% decrease in battery life? From here on out let's settle on 10% (makes math a little easier).

Let me throw in a point that I do not know how to express or define in any kind of context but do want to throw out. It has parallels with CPU's also. If I used a 7200 vs 5400 to do a HDD intensive task and the 7200 was 20% faster note it's per/s per/m consumption was 10% greater? At the end of the day which used more power? In my example the 5400 did? So consider. On to the math as best I can say.

OK startup 5.5w vs 5w? I get 5w as 9% less. Active idle is the only other difference I see 1.0w vs 0.8w so 20% less? I can see that these numbers fail to support Hundreds anecdote with out even going further. I do use my gut at times. Now I must twist the numbers to make scientific and correct. But the basic trend I am seeing already is active idle is 20%? Well 20% of that "whole" is if HDD is 50% of power draw only 10% of the new whole. Well I guarantee HDD is not 50% of total draw after CPU, LCD and as was pointed out to me also WiFi and others like fan, blah blah.

I see a trend and can see Hundred cannot be correct. It is just impossible. If impossible he must be mistaken and if so what is in fact correct. And why, and what conclusions can we draw from such so as to correctly understand and thereby make the correct choice for ourselves. My first belabored point addressed performance. What I find to be misconceptions. This post addresses what I think are common misconceptions by many.

The math (I am not a mathematician I am a 2nd year HS math drop out so I am doing my best) Consider it was stated essentially all is equal and 7200 gets 10% less battery life than 5400. Active idle is the largest disparity 20% more power draw than the 5400. Well 20% more of what? 20% of nothing is 0%. 20% of 10% is only 2% of the whole (100%). That is what triggered my skepticism.

Let me make up a number. Let us assume the active idle HDD uses 30% of the total power consumption (it is intentionally insanely high to avoid nitpicking). 5.5w is 10% increase over 5w or 1.1 of 5w. So we use 10% more of the 30%? Remember it is 10% of the 30% which would be the 5400 (I did not identify 30% is the 5400 but it is) 10% is 3% of the whole (total notebook power draw).

I attempted to use the most favorable numbers to allow Hundred to be correct. I used his low end estimate, I used a very high number for HDD total draw, I used the the least favorable power consumption 7200 vs 5400 not favoring 7200. The best I could get was a 3% difference 7200 vs 5400.

Consider the power draw differential I picked was not a good real world example. For example read/write are the same so 0% difference. That would translate to 0% battery difference. I would say in balanced usage you be under 1.5% maybe below 1% difference in battery life. On a notebook w/3hrs battery life what 5.4 minutes?

I know I took great liberties to express my point. I feel fundamentally sound. If anyone can give insights to flaws I might of made always appreciated. I write to share not be correct. I wrote this cold and am bad at math so not like it will hurt me. I might even learn things. I also want to apologize to Hundred for my, what I thought tongue in cheek response yesterday. You expressed a very common thought that I hope I expressed, better, my issues with. So sorry but I meant no offense. Too much fun typing I guess.

Clear I think 7200 vs 5400 same generation does not matter. Previous post all 7200 and 5400 are not created equal.

Edited by Asus Mobile - 12/22/08 at 8:19pm