Performance: Intel Clover Trail+ SoC

As I mentioned in my review of the MeMO Pad 7, Asus has signed a deal with Intel that has resulted in Intel chips in their entire product stack, including smartphones. With Intel's Moorefield and Merrifield chips still not quite ready for use, Asus has had to resort to a Clover Trail+ chip from 2013. This isn't ideal, as the hardware inside is outdated compared to the 22nm Silvermont-based chips of this year.

The particular SoC in question is the Intel Atom Z2560, which is a 32nm part with a 1.6 GHz dual-core Saltwell CPU, 1MB of L2 cache, a PowerVR SGX544MP2 GPU clocked at 400 MHz, and a 32-bit dual-channel LPDDR2 memory controller providing 8.5 GB/s of bandwidth.

With specs like this, the Z2560 lines up well with Qualcomm's Snapdragon 400 SoC, which has featured in several devices around this price point before, such as the Motorola Moto G. I'm not sure Intel intended their mobile SoCs to be mid-range chips when they launched, with just one chip higher-up in the Clover Trail+ smartphone line, the Z3580, but ARM manufactures have jumped far ahead.

It's worth mentioning that as the Z2560 is an Intel SoC, it uses an x86 microarchitecture as opposed to ARM like the majority of smartphone SoCs. Android 4.3 isn't inherently designed for x86 chips, so Asus has had to use a custom Intel-developed build that is optimized for x86.

Android is naturally at home on ARM chips, so there are some inefficiencies and issues that can arise from porting the OS to x86 SoCs. Some apps are outright incompatible with x86 chips, although this is an infrequent occurrence, and certainly not as much of an issue as when x86 chips were first used in Android devices. More often you'll find that performance in some situations isn't as good as you might be expecting.

Android L is set to address the issues with Android on x86 chips through a new runtime, ART, but the OS isn't available in a final form just yet, and probably won't make it over to the Zenfone 5 in a reasonable time period.

The general performance from the Zenfone 5 is acceptable for an entry-level handset, mostly delivering a smooth experience, but occasionally stuttering. It is possible to multi-task effectively thanks to a surprisingly large 2 GB of RAM included with the device, although there can be a bit of slowdown when loading apps you haven't used recently.

It is possible to game on the Zenfone 5, provided you can get the games to load properly (the x86 architecture can cause a few incompatibilities). The PowerVR SGX544MP2 clocked at 400 MHz has more raw power than the Snapdragon 400's Adreno 305, and is capable of rendering most 3D games at 720p.

Throughout our system and CPU benchmarks, the Zenfone 5's Intel Atom Z2560 sits in between the two Snapdragon 400 devices I've reviewed. On average the device is 18% faster than the MSM8226 in the Motorola Moto G (1.2 GHz quad-core ARM Cortex-A7), but 6% slower than the MSM8228 in the HTC Desire 816 (1.6 GHz quad-core ARM Cortex-A7).

In GPU benchmarks, the PowerVR SGX544MP2 shows itself to be 23% faster than the Adreno 305. GFXBench's Manhattan benchmark refused to run on the Zenfone 5, as does the game Grand Theft Auto: San Andreas which I usually like to test with.

NAND performance is towards the bottom of the table, especially in terms of random read, where it records the worst random write performance of any device I've tested.

The modem included in the Zenfone 5 is Intel's XMM6360, which provides cellular connectivity up to 42 Mbps HSPA+; there's no LTE, but that's to be expected at this price point. You also get GPS+GLONASS, Bluetooth 4.0, and single-band Wi-Fi 802.11b/g/n. Generally I had no problems with any of these connectivity features, although occasionally I'd notice lower-than-expected signal strength.

Internally the Zenfone 5's base model comes with 8 GB of storage, with around 5 GB usable out of the box. This isn't heaps, especially if you plan on installing large games or many apps, but the storage can be expanded upon through the microSD card slot. If you want more internal storage, a 16 GB model is also available.