The 2013 MacBook Air: Core i5-4250U vs. Core i7-4650U
by Anand Lal Shimpi on July 4, 2013 8:00 AM ESTFinal Words
Simplicity permeates Apple from design and software all the way down to the purchasing experience. The 2013 MacBook Air offers only two choices of CPUs, and honestly for the vast majority of the population, that's all you really need. The default Core i5 1.3GHz (4250U) delivers the best overall battery life regardless of workload. Its performance is often somewhere in between a 2011 and 2012 MacBook Air depending on workload, although in some cases it's possible to see equivalent performance to an upgraded 2012 MBA. If you need more performance however, the 1.7GHz Core i7 upgrade (4650U) delivers. In most situations you get more than a 20% increase in performance, bringing the platform up to somewhere in between last year's 1.7GHz Core i5 and 2.0GHz Core i7 options. Once again, with the right workload you could even see performance as much as 20% better than a 2GHz Core i7 from last year. Although I didn't publish any results here, GPU performance seemed roughly unchanged compared to the Core i5 option.
The tradeoff in battery life is pretty easy to understand. In mostly idle workloads, I wouldn't expect any real degradation in battery life compared to the Core i5. Both configurations are equally capable of hitting the same max battery life number. More active workloads however will likely show a 15 - 20% decrease in battery life when paired with the faster CPU. It's possible that you'll see a larger drop with a very aggressive CPU-bound usage model, but at that point I'd assume that you'll probably want to be plugged in regardless of what system you're using.
In previous MacBook Airs, the choice of what CPU to buy was almost always a difficult one. Do you opt for the in-between upgrade or go all the way to the top? With this year's model, the decision is greatly simplified. If you want ultimate battery life regardless of usage model, stick with the base Core i5. If you need performance, the Core i7 upgrade is absolutely worth it. My personal choice would be for the Core i5, but that's because I tend to fall on the battery life side of of the battery life vs. performance fence when it comes to the MacBook Air. If the MacBook Air is going to be your only machine however, I can definitely make a case for opting for more performance.
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FwFred - Thursday, July 4, 2013 - link
Probably the benefits matter much more in non-optimal cases. I think Anand's experience mirrors my own. One bad browser tab can kill the battery life due to javascript or flash. If Mavericks is able to prevent this somehow (not really sure how it could do it within Chrome between tabs, but maybe Safari), I would be very pleased.solmaker - Thursday, July 4, 2013 - link
Thanks for the sage observations, K-Knight. If you're right that Mavericks moves heavier workloads down toward the "light" category, that would tend to decrease the i5 vs i7 battery difference, since they're very close when "light". But I'd think even the "light" case would be helped by Timer Coalescing (batching periodic timer wake-ups) and AppNap (by nailing unused background tasks). My fantasizing about 12 hour MBA 11" battery life was based on anecdotal forum reports of 13+ hour 11" life using the Mavericks beta, but that hasn't been verified. My own usage often has an idle VMware Fusion WinXP session in the background, so I'd get great benefits if AppNap could zap that.KitsuneKnight - Friday, July 5, 2013 - link
Thinking about it more, the light load would also receive some benefit as well. Before when I wrote 'light', I was more so thinking about a system with no apps running, effectively just sitting idle... which is obviously not a 'light' workload, but a no-workload. Although with the current low energy usage of OS X the gains might not be massive (maybe even within the margin of error).I still think the best cases will be with poorly programmed apps with lots of useless timers keeping the system awake, which Timer Coalescing will help a bit with when the app is in the foreground, and AppNap much more so when it's in the background.
I'm not sure how Fusion is architectured, but I /think/ how it works (based on how Workstation was many years ago... on Windows) it won't automagically be able to benefit from AppNap, and VMware will have to put a bit of effort into making it opt into AppNap when appropriate. Parallels Desktop already has a feature where (under the right circumstances), idle VMs will be paused, although it's not as aggressive as it could be.
It'll be interesting to see how developers make their apps work with AppNap (most won't have to do anything beyond linking against the 10.9 frameworks). I imagine at the start many developers will just try to disable AppNap for their app and write blog posts about how 'it's so pointless and doesn't everyone just leave their computer plugged in', before everyone starts embracing it... but maybe I'm jaded from how new technologies get adopted in Windows / Linux land.
solmaker - Saturday, July 6, 2013 - link
Thanks again, K-K. I wonder whether AppNap with be "Opt In" or "Opt Out"? If the latter, then VMware Fusion may automagically AppNap when hidden.fokka - Thursday, July 4, 2013 - link
thanks for the comparison, anand! these are exactly the questions i'm wondering about when researching for a mobile pc: is there a benefit in battery life when chosing a low end cpu, or is the faster cpu just quicker and can even save power with longer idling times?for me it would be clear to chose the i7 here, since it would be be my main computer and battery is similar to the i5 in scenarios most likely with my usage: light workload. but then, if i decide to load up lightroom or want to play a quick game, i can rest assured that i'm eeking out quite a couple percent more performance than on the stock cpu.
now the only thing i'm waiting for is a proper zenbook-refresh :)
ananduser - Thursday, July 4, 2013 - link
I feel you Anand; too bad that other companies don't offer such "one size fits all" lineups like Apple. The exaggerate range of choices from other companies simply adds confusion.I like the detail and effort that went into reviewing different SKUs of the same unit. Hope you do the same for some upcoming items from Lenovo, Asus, Samsung, Sony etc.
Since I mentioned Sony, I want to ask you if there is a chance you could get your hands on the new Vaio Pro and Vaio Duo that sport that "fancy" triluminous display. None of the reviews available has actually gone the length to see what's with that new "quantum dot" tech. Only Anandtech™ can shed light here. What ? Sony hardly sends you Vaios for review ? I dunno, ask them harder ?
Awful - Thursday, July 4, 2013 - link
Thanks Anand, very useful!Any chance of including some GPU/Gaming comparisons too? It would be interesting to see the results of the increased thermal constraints of the i7 on GPU perf (could even be worse I imagine under certain loads?)
ciparis - Thursday, July 4, 2013 - link
If Firefox really takes 17-37 minutes to build, all I can say is wow, what a %$#@! pig.Mackan - Friday, July 5, 2013 - link
Can you also do a battery life test in Windows, via Boot Camp, using pure EFI install which seems to be supported now.US Fiscal Situation - Friday, July 5, 2013 - link
Yeah.. no one else can make thinner and lighter laptops, erm... except for the firms that can and do...Take the Vaio Pro 11, it weighs less (870g), it's thinner and yet has the same battery life.
The Vaio manages to cram in a much higher resolution (full HD) TOUCHSCREEN, NFC and SD card reader. It even has Ethernet support built into the power supply which creates a WIFI hotspot
Both machines are comparable performance/processor wise but one costs £60 less (i7,4GB RAM, 256GB SSD)- No prizes for guessing which.
BTW apropos business use- it should be noted that the lack of boot camp drivers for W8 means that you can't run all of the programs that you might need.
US Fiscal Situation http://bit.ly/16SsEFt