Performance: Snapdragon 800 Power

Like a number of flagship smartphones that have been recently released, the Sony Xperia Z Ultra incorporates Qualcomm's Snapdragon 800 MSM8974 SoC as its main processing powerhouse. This particular model features a 2.2 GHz quad-core Krait 400 CPU, a 450 MHz Adreno 330 GPU and a QDSP6V5A Hexagon DSP at 600 MHz. The DSP is a low-power core that assists the CPU in music playback and media decoding/encoding, and helps keep the overall energy footprint of the chip low.

The MSM8974 also features a range of integrated high-speed connectivity, including a "True 4G LTE World Mode" modem that enables downstream LTE speeds of up to 150 Mbps, Wi-Fi 802.11 a/b/g/n/ac, Bluetooth 4.0, FM radio, and USB 3.0 (where supported by the OEM). The Snapdragon 800 also brings, GNSS (A-GPS + GLONASS), NFC, Quick Charge 2.0 and dual image signal processors. All of these features are incorporated onto the one SoC, manufactured using Qualcomm's 28nm HPm technology.

Alongside the powerful Snapdragon 800 SoC, the Xperia Z Ultra also sees 2 GB of LPDDR3 RAM, and 16 GB of internal storage; although storage can be expanded through a microSD card. Sony has also packed in the usual array of sensors, including an accelerometer and gyroscope, magnetometer, photosensor and proximity sensor.

As you might expect, with one of the most powerful ARM processors available being stuffed into the Z Ultra, the phone is astonishingly fast. Just browsing through the operating system, opening apps and swiping through panes was the fastest I have ever experienced on any smartphone. I first thought Snapdragon 600-powered phones, like the Xperia Z and Galaxy S4, were ridiculously fast, but with the Z Ultra it takes speed to the next level.

Not once was there even the slightest pause when opening an application. Everything loads instantly at your fingertips, and switching between apps using the task manager is the most fluid experience of any. Using the Chrome browser, which can be slow if you don't have the power behind it, provided absolutely no problems, even when viewing content-laden desktop versions of popular websites.

And then there's mobile gaming. Boy, can this smartphone game. Not only is the Adreno 330 simply a speed monster in terms of graphical horsepower, but the 6.4-inch screen also lends itself fantastically to mobile gaming. After browsing the Play Store for some of the top 3D-heavy Android games, I discovered there's nothing that actually can push this system to its limits, save for benchmarks. This means that every game will play smoothly, and you won't have to worry about in game performance ever, despite the need to render to a 1080p display.

A personal favorite of mine, EA's Real Racing 3 received several comments by onlookers about the graphical brilliance of this game. It runs very decently on the Snapdragon 600's Adreno 320 GPU, but any occasional lag is eliminated when I switched to using the Xperia Z Ultra with the Snapdragon 800.

Running both Peacekeeper and Vellamo on the Snapdragon 800 reveals how powerful it really is, streaming ahead of Snapdragon 600 phones by 14-21%. Interestingly, the clock speed of the 2.2 GHz quad-core Krait 400 CPU is actually 29% higher than in the HTC One with its 1.7 GHz quad-core Krait 300 CPU, so we're not seeing performance boosts that are in-line with clock speed boosts. With that said, the Snapdragon 800 is still extremely fast, and the fastest SoC I've used in an Android device.

Qualcomm claimed that the Adreno 330 GPU in the Snapdragon 800 is 50% faster than the Adreno 320, and we saw that with GFXBench. The Xperia Z Ultra delivered a 50% faster result in the Egypt HD offscreen test, and was 53% faster in the T-Rex HD test. I'm not quite sure why the Xperia Z Ultra was 8 frames per second slower in the onscreen test, when it runs at the same 1080p resolution as the offscreen test, but I was able to repeat the same result three times.

The Xperia Z Ultra is the first phone I've reviewed that has been capable of fluid 4K Ultra HD video playback. For the first time I was able to play back by 4K sample video without stutters or audio de-syncing, and although this isn't too important in a world dominated by 1080p content, it's handy for future-proofing the system.

I was also very happy with the audio quality from the Ultra's 3.5mm audio jack, providing a decent balance across the acoustic range. I wasn't impressed with any of the sound effects though, such as ClearAudio+ which "automatically optimizes sound settings", with the default off setting usually providing the best audio. The internal speaker in the device is weak and not very loud, although you shouldn't be needing to use it at any times other than for notification tones.

In what is an unusual move for a review, I'm actually going to complain about a sensor, specifically the proximity sensor. In-call quality and clarity is perfectly fine, as with most smartphones, but the proximity sensor often fails to register when the handset is up to my face. This means that my ears often go through and activate a number of settings in the notification pane, which is very annoying. I believe the issue has something to do with the exact positioning of the sensor and the most comfortable way to use the large device for calls, but it should have been spotted and corrected during testing.

With the Xperia Z Ultra otherwise being a very powerful and capable smartphone, the question now turns to the phone's battery life. The 2.2 GHz quad-core CPU is not going to be particularly friendly to the 11.6 Wh battery when cranked up to maximum clock speeds, which is something I'll explore later on.