As far as I know, and my knowledge in this is limited so do take me with a grain of salt, the current sandybridge i7 used in the mba is rated at 17W TDP (the lower model) while the higher model is rated at 25W. (
http://ark.intel.com/products/54615/Intel-Core-i7-2657M-Processor-(4M-Cache-up-to-2_70-GHz))
And the new ivy bridge have the same 17W TDP.
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Which means that my point is still valid as both SB and IB have the same TDP but as your article points out the performance vs tdp ratio is better in IB. But the battery requirements will likely not go down in the new model.
Again, this is my understanding and it may very well be incorrect.
TDP just has to do with thermal design limits.
With tri-gate 22nm vs the old 32nm technology we should see better efficiency when actually using the CPU. (i.e. it burns less juice to crunch some numbers than when doing the same on SB, it will also finish faster due to performance gains).
Take note, this is Intel claiming this, which isn't saying much with a long history of empty promises. However SB was real. It's amazing to me the balance of performance and efficiency found in that design.
Last night I measured power usage of my MBA 13" and my MBP 13", both Sandy Bridge, both running wifi, browser open. BT disabled. The MBP also has an OWC 120GB SSD.
- The device used to measure was a kill-a-watt with the corresponding power adapter plugged into it.
-At half bright the MBP was pulling 24-27w, the MBA was pulling 29-31w. At full bright the MBP jumped to 29-30w. The MBA went to 39-41w.
I can't really explain why my MBP was pulling less juice...
My point? At idle I think the screen definitely matters more than the CPU. When using it and actually burning CPU cycles you're using more power. Yeah, they probably won't realize a lot of extra battery life, under use I anticipate maybe an hour extra battery life on the 11", maybe an hour and a half for the 13's. Another possibility is they take the power savings and shrink the battery size a bit. 20% reduction in weight and size would be appealing, but I would take the extra battery.
I do know this, under typical business usage (for me), I get about 7.5-8 hours out of my MBP. About 6.5 out of the 13" MBA. And I haven't tested the 11" MBA thoroughly enough, about would guess I would get a solid 4-4.5 hours for my typical day. This is a couple notches about half-bright (depends on what office I find myself in that day).
Anyway, assuming there is still a 13" MBP this year it's going to be a contest between it and the 11" Air. If they find a way to sneak an extra hour into the 11" MBA I'm leaning heavily toward that.