The following article (http://www.notebookcheck.net/Review-Intel-Core-i3-i5-i7...) suggests that the i7-620m uses significantly more power in all conditions than the i5 processors. This seems quite strange given that the primary difference between these processors is 1MB of cache; all else seems nearly identical. Or are there other differences? I'd like to go with the i7 on my next laptop, but the increased power consumption (if accurate, and not just a testing or driver issue) is really worth the tradeoff of significantly increased power usage.
The I7 is overkill for a laptop it uses way too much power like the article says. Depending on which I5 you are looking at the difference could be hyper threading some I5s have it some dont also the I5 is actually newer then an I7 so they improved on its power consumption with the newer chips.
I agree that the i5 is probably the better call, but I've noticed in the math intensive applications that I run every bit of cache helps, so ideally the i7 would be better (but not if it uses 25% more power). It just doesn't make sense to me that the i7-640m (2 cores) uses so much more power than the i5's which appears to be a nearly identical design. thx, g-
Along the same thread, how about the Core I5-520m compared to the compared to the i7 ULM processors. I have yet to see how much power the i& ULM draw in comparison, but the i5 may still be a better porcessor. Intel sure makes this complicated. g-
That graph is deceptive, yes the i7's peak power consumption is more, but it will complete the work load quicker meaning it uses few watt-hours in the end which is what you really care about. Peak power consumption is important when it comes to cooling needs, but rarely will you run at peak and when you do you will get the word load done faster and will sit idle more often. They also did their power test with prime 95 running 8 threads in the most power consuming mode, you will have an incredibly hard time putting that kind of load on your cpu with normal usage.
How often are you planning to take this laptop far away from its charger? If you are like me and bring its charger with it at all times it really doesnt matter if you have 1 hour of battery life or 15 as it will probably never get close to running out of battery if you plug it in fairly often.
Look for the performance you need, then worry about the power consumption.
You make a good point, but my concern is the idle power usage. When I do heavy processing (python scripts, etc) my laptop is plugged in. But a lot of times it isn't plugged in and I'm using it for very simple tasks, e.g., email, web, etc. The i7 appears to use almost 30% more power in idle type scenarios which I think outweighs the advantages of a little more speed and cache. It is strange that the idle power usage would be so diffrent.
Here is the power section quoted from the article:
Although Intel states a TDP (Thermal Design Power) of 35W for all tested chips, the nominal power consumption turn out very different in the single tests. The total system's power consumption was measured between the mains and the adapter in following performance profiles: idle min. (energy savings mode, min. display brightness), idle max. (high performance mode) and under CPU load (high performance mode, Prime 95 Torture Test – in-place large FFTs).
As you can see on the recorded measurements, Intel's Core i5 chips are all very close to each other in idle power consumption and the maximum power requirement and barely differ. The test system consumes about 30W more from the mains under load. The Intel Core i3 CPU proves to be a bit more humble under load, as it then treats itself to about 4W less than the i5 chips.
Even if the i5 processors have a slight lead in many exercises in terms of performance, the i7-620M CPU reveals itself as being especially energy devouring. The CPU treats itself to about 15W more, with up to 64.7W under load, than the i5 colleagues. The test system also needs around 10W more in idle mode with 30W than the configuration with a Core i5 chip.
i7-620m using more power in idle is BULL CRAP. Whatever crap site that did the experiment should get their system straight. Shame on them.
I have a i7-620m in my sony Z. With max brightness, Windows 7 power profile set as Balanced, it only consumes 12 Watt off the wall. I used Kill-a-watt to measure this. If you consider the efficiency loss of the AC adapter, I think it is well within the range of core i5's.
Of course, under load, it's gonna be a different story since i7-620m can go to higher clocks. This will consume more power, but get the job done that much quicker.