Sandy Bridge battery life - dual core vs quad core

I intend to buy a new laptop this year, following the lauch of the much-anticipated Sandy Bridge. I bought my last laptop, which sports a Core 2 Duo T8300 2.4 GHz processor, in 2008, and, although it still handles most tasks quite well, I could definitely benefit from a significant speed boost. However, this decision became more imminent since my laptop had its screen damaged last week. I can certainly have my screen repaired, but that there is no point in fixing it if I am going to replace the laptop anyway.

I've noticed that there are some new laptops with a quad-core Sandy Bridge processor. I've read some tests and even the i7-2630QM (which represents the low-end of these processors) seems to be faster than any Clarksfield (even the almighty i7-940XM).

In addition, this processor seems to be more power-efficient than the Arrendale. I've read reports that a Sager NP5160 sporting an i7-2630QM has a battery life of 4.5-5 hours or even 6 hours (with NVIDIA GT540M disabled). That's a lot of time, considering that the battery of previous Sager notebooks would be drained after only 2 hours of use or even less.

I understand that this increase in battery life comes, to a large extent, from the gymnics Intel has done with its integrated graphics. However, as far as I am concerned, quad-core processors still consume more power than dual-core processors. A Core i7-2630QM has a TDP of 45W; the dual-core Sandy Bridge, on the other hand, will have a TDP of 35W. I have no doubt that the dual-core Sandy Bridge would be more power-efficient than the quad-core. But I wonder how much more efficient it will be.

I am not aware of any tests or reviews of dual-core mobile Sandy Bridges nor of any report of Intel on this respect. No real facts, just thoughts posted in forums. I've read thoughts that a dual-core Sandy Bridge would allow notebooks with an 8-hour battery life. But I've also read that most of this power efficiency comes from the integrated graphics and that a dual-core Sandy Bridge would not allow a significant increase in battery life over the quad-core Sandy Bridge (it would be about half an hour). While I believe the truth is in the middle, I would like to further investigate this matter, so I can decide whether to buy a laptop with a quad-core Sandy Bridge now or wait until the dual-core is available.

Any thoughts on this issue? I would much appreciate if someone had more information (real facts) on this. Thank you in advance.

 

The short answer is that there are no reviews of dual-core Sandy Bridge laptops yet and thus we do not know their battery life. Wait until February.

The longer answer is that we can sort of extrapolate from what we know about the quad-cores. You are not entirely correct: the long battery of quad-core Sandy Bridge comes not merely from an efficient integrated GPU, but also from state-of-the-art power gating. Look at the chart on the bottom of this page -- the idle power consumption of even the high-end desktop Sandy Bridge is tiny (around 5W). Intel manages to do this by switching off circuits that aren't needed for the situation at hand. For example, you don't really need all 4 cores when you're browsing the web.

As a result, I would not expect a massive difference in battery life between standard voltage quad-cores and dual-cores. However, low voltage CPUs are different: they're binned chips that can do the same with less energy so there's an extra layer of efficiency there on top of the power gating. This is where I suspect the 8+ hour laptops will come from.

 

The low power consumption chips just use less energy by running at lower voltages and lower frequencies. There is nothing special about binning them unless normal chips aren't capable of running at the same settings, but that is extremely unlikely. Plus since normal laptop processors are getting a lot more energy efficient, these low voltage chips just seem less useful every day.

 

Yes, that's straight to the point. And I can only know for sure when the first dual-cores pop-up.

Yes, I suspect that there the long battery of Sandy Bridge comes from more than efficient GPUs. However, I looked at the chart you mentioned, and I noticed that the Sandy Bridge i7-2600 consumes 5W when idle, while the Lynnfield i7-880 consumes only 3W. Sandy Bridge may handle energy consumption better than Nehalem, though.

Yes, there are low voltage chips. But these chips run at lower frequencies and/or cost more. The point in getting a quad-core is to have lots of power packed in a notebook. The battery life of low-voltage chips may be better, but I can't deal with the performance penalty. However, I could use a Core i7-2620M instead of a Core i7-2630QM (the performance difference won't be that much, I guess) if the battery life is greatly increased.

 

I found the issue with low power CPU's is the voltage, which requires binning of CPU's because some CPU's simply will not go lower then an individual voltage no matter the frequency you set it at.

For example my first Phenom II 550 x2 went as low as .93v~ @ 800 or 1200 mhz, anything lower caused a BSOD no matter the frequency. Yet a 2nd II 550 I got as a replacement went as low as .815 @ around 1.2 ghz IIRC, Prime95 stable. Same setup, underclocking was done via multipliers.
It really varies, individual processor to processor.

 

My SB Quad Core laptop has 3h battery life (6 cell) with wireless on. My old i5 Dual Core didn´t get to 2,5h.

 

I have a 2720QM with integrated graphics and seem to be getting about 6 hours of light (read non-video streaming) web browsing on a 61WHr 6-cell battery. Per RMClock during idle on lowest brightness the discharge rate drops below 8W and I've seen its estimates over 8 hours of battery life. Needless to say I'm impressed.

 

Idle power consumption from Intel has been pretty good for a while now. Even my desktop quad Nehalem i7-860 would use ~5W idle provided C3/C6 was enabled and Vcore wasn't fixed too high.

 

My 970 is great on power consumption too. I disabled EIST and C1E, and it's running full blast @ 3.2 GHz 24/7.

But in all seriousness, it's all dependent on the binning process! Though I have yet to figure out how to undervolt my SU7300...RM clock doesn't like it

 

That's great information, thanks! Quad-core Sandy Bridges look great!

Do you have any idea on the difference in battery life between the i7-2630QM and the i7-2720QM? The only information I have is the difference between the i7-2630QM and the i7-2920XM (at the bottom of the page in this link: Review Intel Sandy Bridge Quad-Core processors - Notebookcheck.net Reviews). But the i7-2920XM has a TDP of 55W compared to 45W in the i7-2630QM and the i7-2720QM. I could benefit from the improved TurboBoost of the i7-2720QM (up to a whooping 3 GHz in quad-cores, compared to 2.6 GHz in i7-2630QM), as long as it does not drag much power...

In addition, I've noticed that the integrated graphics of the i7-2720QM runs at 1300 MHz in Turbo Mode, while the i7-2630QM runs at 1100 MHz. How does it impact battery life?

 

There won't be a noticeable difference in battery life, neither from the higher CPU clock nor from the integrated graphics turbo.

 

While TDP is used as a maximum guideline, don't use it as any measure of power consumption. In general, CPUs of a same generation use more power when increasing clock speed and cache. While this isn't much for each step up, it can add up when you're comparing a few hundred MHz and a couple more MB of cache. This especially depends on what type of system you use - a 12" ultraportable will notice a 1W difference a heck of a lot more than a 17" DTR. You can see this in any of the numerous desktop Sandy Bridge CPUs (just scale the power consumption proportionally down for notebooks):

The Sandy Bridge Review: Intel Core i7-2600K, i5-2500K and Core i3-2100 Tested - AnandTech :: Your Source for Hardware Analysis and News

 

Just off topic: But what about heat of quad core processors Vs dual core processors. 1st gen i-series quads were producing more heat than dual cores. So what will be for SB quads and dual cores ?

 

Quad cores will still create more heat than dual cores because there are a lot more transistors at work. According to Notebookcheck the SB -QM models are 45W parts. Also, if all 4 cores are heavily loaded the maximum speed will be below the rated maximum speed.

John

 

The first test of an i7-2620M is in, and it comes in the form of a Micro Express NLB26. Apparently, that laptop could only get about 3.25 hours of battery life. OK, I'm not sure what kind of battery it is using but I'm guessing it is a 6 cell. Not very impressive if you ask me.. I was expecting a lot more improvement with the long awaited Sandy Bridge.

Micro Express NLB26: Mostly Unremarkable - Computerworld

 

It comes with a mid range discrete GPU 3.25 hours is fine.

 

I can only call that a travestite, there is no way that anyone can call that a review, even my cat understands more about what it needs to be shown in a review.