Background

The Macbook Air has come a long way since its introduction back in 2008. The Macbook Air was suppose to be thin, light and portable while still offering full notebook performance and excellent battery life. Unfortunately, it was far ahead of its time, and the technology which was suppose to make it happen didn’t exist in the easily available quantities as it does today. Although the subsequent chassis redesign in 2010 and the introduction of an 11 inch model was substantially better, the MacBook Airs were still limited by their power hungry processors and poor battery life on the 11 inch model.

The same can’t be said for the 2013 MBA. Intel has shifted its focus considerably towards the mobile end of the market once again in response to the ARM threat which has resulted in a chip which seems perfect for Macbook Air’s form factor offering decent performance at a very low power consumption.

Battery

I’ll focus on battery performance in the first part of this review, because if you’re considering an upgrade, this would be the reason. Haswell offers many features which dramatically improve platform efficiency (outlined later), but the result is an impressive runtime, even by tablet standards.

Situation	2012 Ivy Bridge	2013 Haswell	Haswell Advantage
Idle + Display Off (Wi-fi on)	11.8h	29h	146%
Idle + Display On (Medium brightness, Wi-fi on)	9.3h	14.5h	56%
Light Workload (Medium brightness, Web browsing including Youtube, music in background)	5.3h	9.8h	84%
Heavy Workload (Batch processing images, uploading/downloading at ~1MB/s to server, music in background)	2.2h	4.2h	91%
Maxed Out (Loop Cinebench)	1.4h	2.1h	50%

*Runtimes for 2012 MBA adjusted for battery condition. Both running OSX 10.8.5.

These numbers are impressive in their own right, especially when compared to the previous generation Ivy Bridge Air. Haswell offers almost double the runtime over Ivy Bridge on a battery roughly the same size. With more than 6 hours of real world use, the 11 inch Air could be used much like an iPad or iPhone; simply take with you in the morning and charge at night. It is worth noting that even in the heavy workload test, the 11 inch Air still delivers over twice the performance of its predecessor, possibly due to Haswell’s aggressive switching between C states. Because of this, I’ve also tested the Air’s battery when the system is completely maxed out, and here battery life drops to 2.1 hours, which happens to be roughly the same as last years Air on the heavy workload test. This level of dynamic range in performance/power consumption is incredible for an x86 notebook, and even holds up well to the ARM competition.

The 11 inch Air has always been a compromise between small size and sub-par battery life, and it’s safe to say that Haswell fixes this.

A somewhat smaller impact in battery life comes from a higher operating voltage of the battery, 7.6V this year compared to last years 7.3V which allows an extra ~3Wh in capacity. A higher operating voltage in Lithium cells usually results in higher stress and lower operating lifespan unless newer manufacturing processes are used. Thanks to the smaller battery and a more than sufficient 45W adapter, the 11 inch Air charges in 2 hours, much faster than the iPad 4 with its 45Whr battery. This is a nice example for using energy efficient components rather than huge batteries.

It is interesting to see how a Haswell ULT system like this behaves in terms of power consumption during everyday workloads. Being a Haswell ULT system, 2013 MBA’s idle power consumption (display half brightness) is a mere 3.4W. To put this into perspective, the iPad idles at 4W and most Ivy Bridge Ultrabooks idle at 5W. Being a full x86 system however, the system can draw up to 20W under full load when you need the performance (the CPU/GPU itself can draw up to 25W during Turbo despite having a 15W TDP). Most light workloads (web browsing, local video, music etc) see the system drawing under 5W, much lower than last years 9.5W.

It’s not just the low idle power consumption that contributes to the increased battery life, it’s the amount of time the CPU can spend being idle. Haswell is able to maximise idle time by aggressively switching between power saving C states, and this is enabled by the use of fiVRs.

Performance

The short story is that this years MBA doesn’t perform noticeably faster than last years model. However, it is important to take this in context that there are many things working against this years Air in terms of performance. The first and possibly most important are thermal limitations.

Last years Ivy Bridge chip had a 17W TDP, thats 17W for the CPU, 16 EU GPU and the L3 cache amongst other things. The PCH as well as the VRs were placed off-chip and had little impact on the thermals of the CPU, so by Ultrabook standards Ivy Bridge had a comfortable thermal range to perform.

Haswell ULT is a different story. At 15W TDP, not only does the Haswell CPU have a lower TDP, but it has to share this with both the on-chip PCH, fiVR and a considerably beefier 40 EU GPU, meaning frequency and voltage scaling to achieve higher performance are constrained. Of course, integrating the PCH and the use of a fiVR offers huge power savings (for example by allowing the CPU/GPU/Cache to switch aggressively between power saving states) contributing to the stellar battery life seen earlier, but it does limit sustained performance.

Burst performance with Turbo Boost however is similar, if not slightly better than last year. By operating at a lower power when idle, Haswell is able to build a “thermal budget” more rapidly than Ivy Bridge, and can therefore Turbo to a higher clock speeds and duration than Ivy Bridge improving system responsiveness. My i7-4650U occasionally jumps to 26W if thermals allow.

In terms of real world performance on an 11 inch machine, Haswell offers more than enough computing power for everyday tasks. In fact, I would be comfortable with Sandy Bridge levels of performance on a machine like this. Unless you’re rendering videos or working on huge RAW files, the 11 inch Macbook Air should give you all the performance you need. I’m not a gamer, but the Air with its GT3 (40 EU, no eDRAM) handles older titles like Bioshock very well. Finding a GT3 configuration in an Ultrabook is quite rare at the moment (even the Surface Pro 2 uses GT2), and the high number of EUs makes for a more power efficient GPU (GPU workloads are highly parallel after all) but does increase the cost.

If you’re going to find any significant performance increase over last year’s Air, its going to be the SSD. Many high end SSDs on the market are able to reach the peak bandwidth of SATA 3 (6Gb/s), and it has become apparent that SATA 3 is becoming a bottleneck to storage performance. SATA 4 (12Gb/s) should offer better performance, but that’s not out yet. To increase storage performance, Apple opted to use PCIe instead (much like the 2013 Vaio Pro), which offers considerably higher bandwidth than SATA 3. It is likely that the storage bottleneck is once again the NAND controller. Speaking of, due to the high volume of shipment of Airs, different SSD suppliers are used so performance across devices will vary. Being SSDs, factors like wear, spare area and TRIM have an impact on performance as well.

A simple disk speed test using Blackmagic’s Speed test reveals the 512GB model (Samsung SM0512F) provides sequential reads/writes at 830MB/s and 790MB/s respectively. This is blazingly fast even by SSD standards, and almost saturates the 2 PCIe lanes the SSD is given (1GB/s up/down). I haven’t tested the 256GB or 128GB versions, although I would expect the 256GB model to perform similarly. Due to the lower number of NAND die to exploit parallelism, the 128GB model may perform slower.

In everyday use, its quite hard to notice the difference an extra 300MB/s or so, however tasks such as waking from sleep or boot times are noticeably better than last years Air. The 2013 Air is truly an instant on device; it is ready to accept input even before you could manage to get the lid fully open, whereas last years Air had a slight delay before you could use it. It doesn’t seem like much of a difference, but it affects the way you use the device in a huge way. The Air would easily replace an iPad in situations where you quickly need to look something up, and being a full computer, you have much greater flexibility with what you do with it.

Apple offers 2 CPU options for both the 11 and 13 inch models. The upgraded i7 model offers a slightly higher base clock speed (1.7GHz as opposed to 1.3GHz) and turbos up to 3.3GHz depending on thermals. The performance difference is noticeable in everyday tasks, and the boost in single threaded performance is apparent in system responsiveness however it doesn’t really change the way you use the notebook. We’re still talking about a 15W CPU after all. If you can, I would advise on the BTO 8GB RAM model, which should offer some future proofing as RAM cannot be upgraded later on. The SSD is technically removable, however because the form factor and interface changes between generations, finding an upgrade may be difficult and costly, so I’d recommend that all upgrades should be purchased up front.

Display

This part of the review could apply for all 11 inch Airs back to 2010, as not much has changed with the display on the 2013 model. It’s still a 1366*768 TN panel offering decent colour reproduction and contrast for a consumer display, but it’s 2013, and IPS displays are no longer an expensive reserve for those requiring colour accuracy. To be honest, it’s not the lack of “retina” resolution that affects user experience with the Air, but other factors like colour and contrast. At 132ppi, the Air’s panel is quite sharp for an 11 inch display. I’m not saying this with nievity as I use a retina display iPhone and mac nearly every day. Quadrupling the pixel count on the 11 inch air would simply create more work for the GPU and backlight for what in my opinion would be a small noticeable gain in sharpness. Quadrupling the pixel count on something like a standard MacBook Pro made more sense because at 113ppi, pixels were much more noticeable back then. Increasing the resolution without 4×4 scaling would just make everything smaller than what is practical. If Apple were just to replace the 11’s panel with an IPS display of the same resolution, I would be satisfied.

I do feel however that Apple would be obligated to use retina displays in next years Airs, and it is most likely that the power consumption would be offset by Broadwell’s power savings or the use of IGZO panels. From a power consumption standpoint, next years Air may be very interesting and hopefully we’ll see Panel Self Refresh (PSR) technology which would drive power consumption even lower.

One point which I would like to go into however is reflectiveness of the display. Unlike the non-retina Macbook Pro’s, the Macbook Air doesn’t use a cover glass which means no air gap between the glass and the LCD. One of the major problems I’ve had with the old non-retina Macbook Pro (and even the iPad/iPad Mini) is poor outdoor performance. In adverse lighting conditions (think direct sunlight/glare), the Macbook Air’s display appears significantly better even if technically it uses a lower quality TN panel.

I like the direction Apple is taking with its Retina Macbook Pro’s and iMacs by optically bonding the cover glass to the LCD, which results in a display which performs well in real world conditions as well as on paper.

The 11 inch form factor

As a person coming from a 13 inch Macbook Pro, moving to an 11 inch Air represents an interesting change in how the system is used, and most of the time the change is positive. My old Pro weighed slightly over 2kg, and unlike an iPad I had to make a conscious decision on whether to carry it with me or not due to its weight. The 11 inch Air is just over half the weight of the 13 inch Pro, and this makes a huge difference in where I carry the system. Anywhere an iPad could go, the 11 inch Air would replace it just fine, and being a full computer I could do an awful lot more with it.

As an everyday machine however, the 11 inch Air is a tad on the small side. After using the Air for 2 weeks, I still think that 13 inches is the sweet spot for a notebook in terms of usability and portability. I don’t mind the 16:9 aspect ratio but it’s the physical size of the display that affects productivity. I find myself using my external monitor more often with the 11 inch Air, and with Mavericks around the corner this workflow should become more effective. Compared to the Surface Pro which I used for a few weeks however, the 11 inch Air makes more sense; it is just as portable and can be used comfortably on your lap (something which can’t be said for the Surface)

Should you upgrade?

If you’re already an owner of a Macbook Air and battery life is a priority, then this years Haswell MBA’s should be a no brainer purchase. With this years Airs, you’re essentially getting about the same CPU performance as last year, but with double the battery life, with additional improvements to storage and GPU to boot.

If you’re the owner of an Ivy Bridge (2012) or Sandy Bridge (2011) MBA and are happy with battery life they offer, I would hold off purchasing the Haswell MBA and wait for Broadwell (2014) which should offer even better battery life and significantly better graphics (Haswell after all uses the same GPU architecture as Ivy Bridge, but simply adds more EUs).

Those using ~2009/2010 Core 2 Duo MacBooks (both Pro or Air) would find the 2013 MBA a substantial upgrade in terms of performance. Haswell supports features such as Turbo Boost, a higher IPC as well as additional extensions such as AES-NI, making even Haswell ULT significantly faster than any 2010 Core 2 Duo Macbook in terms of CPU performance. The 1.7GHz i7-4650U in the 2013 Air performs over twice as fast as my old 2.4GHz Core 2 Duo P8600 in Geekbench, primarily by faster memory bandwidth, hardware support for more extensions and Turbo boost.