| Part 2 of this review is here
The question many are asking is:
- If I choose the i7 will I have a noisy fan system having trouble keeping cool?
- If I choose the i7 over the i5, will I have significantly lower batter life?
- If I choose the i7 over the i5, will it be significantly hotter to touch than the i5?
- How much more powerful is the i7 and is it worth any concessions in any of the above?
Some comparisons out there compare the upgraded i7 (with double the ram and disk) to the stock i5. This comparison, while reasonable, is not 100% accurate for exact same systems.
In order to do a fair comparison, both systems should have the same exact hardware with exception to the CPU. I personally ordered the Mac Book Air 11" 2012 i5 with 8GB ram and 256GB SSD upgrades. After having second thoughts and no forum or review truly addressing the battery, heat, & fan noise head on I relented to going out and getting an upgraded MacBook Air 11" 2012 i7 with 8GB ram and 256GB SSD to compare them head to head.
To ensure the machines were identical, I cloned the drive of my i5 and immediately restored it onto the new machine. This ensures as close of a controlled test as possible under the circumstances.
Pre-Test Stats
Before starting the tests, I let the machines idle for a long while and then checked the stats with iStat Pro. The results are:
| MacBook Air 11" 2012 i5 | MacBook Air 11" 2012 i7 |
|---|
 |
 |
|
Temps:
36 - HD
40 - CPU
28 - Enclosure Base
28 - Enclosure Base 2
28 - Enclosure Base 3
30 - Heatsink B
36 - Mem Bank A1
37 - Mem Controller
Fan:
2004 rpm
|
Temps:
37 - HD
42 - CPU
29 - Enclosure Base
29 - Enclosure Base 2
30 - Enclosure Base 3
31 - Heatsink B
39 - Mem Bank A1
38 - Mem Controller
Fan:
2001 rpm
|
Test #1 - FAN SPEED & NOISE
These MacBook Air's have a similar asymmetrical fan the MacBook Pro Retina has, however only one can be fitted into the small form factor. I can attest the sound is significantly lower and practically inaudible up to 3500rpm. There after it's still very low up until about 5000 where you start to notice the whirling sound -- still much less when compared to the 2011 model at the same RPM.
The test was an approximate 30 minute encoding of a video project using ScreenFlow with both the source media on the Desktop (SSD) and the encoding saving also to the desktop. Both MacBooks have the Samsung 256 SSD so there should be no differences in energy consumption or heat there.
The results:
| Time | MacBook Air 11" i5 | MacBook Air 11" i7 |
|---|
| |
Fan Speed |
CPU Temperature |
Encoding Time Left |
Fan Speed |
CPU Temperature |
Encoding Time Left |
| 0:15 |
1997rpm |
48 celcius |
38 min |
2001rpm |
48 celcius |
33 min |
| 2:36 |
2001rpm |
89 celcius |
--- |
4305rpm |
105 celcius |
--- |
| 6:12 |
-- |
-- |
36min |
-- |
-- |
29min |
| 7:16 |
3110rpm |
91 celcius |
--- |
5943rpm |
97 celcius |
--- |
| 8:55 |
3563rpm |
89 celcius |
-- |
6500 rpm |
93 celcius |
-- |
| 11:31 |
-- |
-- |
31 min |
-- |
-- |
23min |
| 12:43 |
-- |
-- |
29min |
-- |
-- |
21min |
| 17:02 |
-- |
-- |
25min |
-- |
-- |
17min |
| 17:40 |
5162rpm |
81 celsius |
-- |
6499rpm |
91 celsius |
-- |
| 23:32 |
5593rpm |
78 celsius |
-- |
6499rpm |
91 celsius |
|
| 30:00 |
6128rpm |
76 celsius |
-- |
6494rpm |
92 celsius |
-- |
| 33:02 |
6418rpm |
74 celsius |
-- |
6497rpm |
92 celsius |
-- |
Conclusion, the i7 cpu heats up quickly spooling the fans of the i7 earlier. At the 2:36 mark, the i7 was at 4305rpm while the i5 was still at a silent 2001rpm. At the 8:55 minute mark, the i7 reached maximum rpm of 6500 while the i5 was still at a comparatively low 3563rpm. The i5 almost reached the 6500 rpm mark after 33 minutes of heavy lifting however although it didn't really need to because the CPU was progressively lowering in temperature when compared to the i7 remaining firm between 91 & 92 degrees. The i7 also was significantly ahead with regards to getting the job done. Initially the i7 was ahead by about 5 minutes and inched up to be about 7-8 minutes ahead by the middle and ending of the encoding.
Outside Temperature of MacBooks:
Good news for those worrying about the outside temperature. In both the i5 and the i7, there was very little difference in surface temperature -- by only one or two degrees at most. They both felt warm to the touch. Neither felt too hot to hold, however the i7 was every so slightly warmer. Without one to compare with, I wouldn't be able to tell you which one I was holding.
Test #2 - Battery Drain Stressful Load
For this test, I simply unplugged the power cords and re-ran the same exact video encoding. I didn't take specific time stamps, however i did compare them both simultaneously at varying intervals. On the video, the iPhone was really close to both MacBooks so the microphone was much closer and audible than one would normally perceive and additionally, there were two MacBooks working side by side.
| |
MacBook Air 11" i5 |
MacBook Air 11" i7 |
| Take 1 |
94% Charge |
92% Charge |
| Take 3 |
89% Charge |
85% Charge |
| Take 4 |
74% Charge |
65% Charge |
| Take 5 |
71% Charge |
60% Charge (finished encoding)) |
| Take 6 |
65% Charge (finished encoding) |
-- |
Conclusion, the i7 gets more work done faster at a small cost in battery. Both machines did the same work, the i5 finished with 65% battery left while the i7 finished with 60% battery left. Under stressful load, I consider this a very good feat given the performance gains achieved. These stressful scenarios are not the norm and instead you may be working casually more often than not so I expect the difference in battery to be even lower during normal use. As a matter of personal opinion, I didn't like seeing the i7 pegged at 91 degrees under normal room temperature while the i5 was progressively being reduced from a peak of 91 degrees down to 74 degrees near the end of the encoding.
Test #3 - Battery Drain Light Load
For the light load tests, I simply created an HTML page with an auto refresh every 10 seconds loading USAToday web site. I turned off the brightness on both monitors to isolate the drain to the CPU as much as possible and left them alone for a few hours.
The Results:
| |
MacBook Air 2012 i5 |
MacBook Air 2012 i7 |
| Take 1 |
98% Charge |
98% Charge |
I had to go to bed and before wrapping up; tentatively there is very little difference (1% or 2 down to 75% -- with the i7 obviously consuming a bit more). Prior to going to bed, I started to use both macs side by side performing the same operations. Launching a VM, browsing, refreshing, performing browser speed tests, etc. and I was able to bring the MacBooks down to a difference of 5% (i5 had 55% and i7had 50% battery left). I will have some additional updates on normal and light loads in the coming days.
Overall Conclusion
The overall conclusion is very subjective and different for everyone. If you have a thunderbolt display and/or plan to use the MacBook air as your primary machine with large SSD drive, then i7 may be the way to go. If on the other hand the MacBook air is your secondary computer and you have a performance oriented iMac at home or office, then other factors such as battery and/or comfort should have higher significance. Below are my summary conclusions based on my findings.
FAN Noise - Those wishing to have as silent of a computer as possible in most circumstances should opt for the i5. Keep in mind however, I've been using the i7 all day today -- plugged into a 27" display and have yet to hear it spool up. In order words, just as the test showed, under specific load, the i7 will spin up the fans within a few minutes while the i5 will take a little longer to do so -- however you need to produce load on a sustained basis for that to occur. If you are dead set on having minimal fans then i5 gives that, but be forewarned the i5 will spool up eventually (8-12 minutes later rather than 2 minutes).
Surface & bottom chassis temperature -- both MacBooks are only off by a degree or two. It's noticeable only if you are comparing one with the other. I wouldn't be able to discern which MacBook I was holding in my hand under load otherwise. If you are only concerned about temperature, there is negligible difference and should ignore this factor and move on to the next important factor. Despite this, do read my comment on CPU temperature below under other ambients.
Battery -- Under heavy load, the i7 drew about 15% more battery (5% difference in battery level at the 60-65% level). Given the performance results indicated a 30% improvement with i7 over i5 (25min left vs. 17min left at the 17 minute mark), the bang for the buck seems to be there. Note, this was a heavy IO test using the optimized SSD which we all know is significantly faster than the previous model, so true performance difference between machines, as per standard benchmarks, is somewhere 15% mark. If you do edit video or have heavy IO tasks, using say the 512MB SSD, then certainly the i7 gets you a noticeable improvement and should opt for it. For those seeking maximum battery life, the i5 will give you some extra juice -- approximately 10-15% if used under load continuously. Under very light load, the batter difference seems to be a negligible < 5%. So under normal load, you can probably expect 7-10% extra battery life on the i5 vs the i7.
CPU Temp -- I did notice the CPU temperature for the i7 was pegged at 91-92 degrees under load at room temperature. The i5 was actually lowering the CPU temperature while slowly increasing the fan speed. Because of this, if you are working in environments where the temperature may be ambient, say out side patio on an afternoon, you may find the i7 is not able to keep the CPU cool causing the system overall to become hotter -- again only under load. The i5 would also have the same effects, but to a lesser extent.
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