Revisiting SHIELD Tablet: Gaming Battery Life and Temperatures

While the original SHIELD Tablet review hit most of the critical points in the review, there wasn’t enough time to investigate everything. One of the areas where there wasn’t enough data was gaming battery life. While the two hour figure gave a good idea of what to expect in terms of the lower bound for battery life, it didn’t give a realistic amount of time for battery life

One of the first issues that I attempted to tackle after the review was battery life performance in our T-Rex rundown when capping FPS to ~30, which was still enough to exceed the competition in performance, and avoid any chance of throttling. This also gives a much better idea of real world battery life, as most games shouldn’t come close to stressing the Kepler GPU in Tegra K1.

By capping T-Rex to 30 FPS, the SHIELD Tablet actually comes quite close to the battery life delivered by SHIELD Portable with significantly more performance. The SHIELD Portable also needed a larger 28.8 WHr battery and a smaller, lower power 5″ display in order to achieve its extra runtime. It’s clear that the new Kepler GPU architecture, improved CPU, and 28HPm process are enabling much better experiences compared to what we see on SHIELD Portable with Tegra 4.

The other aspect that I wanted to revisit were temperatures, I mentioned that I noticed skin temperatures were high, but I didn’t know what they really were. In order to get a better idea temperatures in the device, Andrei managed to make a tool to log such data from on-device temperature sensors. Of course, the most interesting data is always generated at the extremes, so we’ll look at an uncapped T-Rex rundown first.

In order to understand the results I’m about to show, this graph is critical. As ambient temperatures were lower (15-18C vs 20-24C) when I ran this variant of the test, we don’t see much throttling until the end of the test where there’s a dramatic drop to 46 FPS.

As we can see, the GPU clock graph almost perfectly mirrors the downward trend that is presented in the FPS graph. It’s also notable that relatively little time is spent at the full 852 MHz that the graphics processor is capable of. The vast majority of the time is spent at around 750 MHz, which suggests that this test isn’t pushing the GPU to the limit, although looking at the FPS graph would also confirm this as it’s sitting quite close to 60 FPS throughout the run.

While I was unable to quantify skin temperature measurements in the initial review, battery temperature is often quite close to skin temperature. Here, we can see that battery temperatures (which is usually the charger IC temperature) hit a maximum of around 45C as I predicted. While this is perfectly acceptable to the touch, I was definitely concerned about how hot the SoC would get under such conditions.

Internally, it seems that the temperatures are much higher than the 45C battery temperature might suggest. We see max temperatures of around 85C, which is edging quite close to the maximum safe temperature for most CMOS logic. The RAM is also quite close to maximum safe temperatures. It definitely seems that NVIDIA is pushing their SoC to the limit here, and such temperatures would be seriously concerning in a desktop PC, although not out of line for a laptop.

On the other hand, it’s a bit unrealistic for games not developed for Tegra K1 to push the GPU to the limit like this. Keeping this in mind, I did another run with the maximum frame rate capped to 30 FPS. As even the end of run FPS is over 30 FPS, showing the FPS vs time graph would be rather boring as it’s a completely flat line pegged at 30 FPS. Therefore, it’ll be much more interesting to start with the other data I’ve gathered.

As one can see, despite performance near that of the Adreno 330, the GPU in Tegra K1 sits at around 450 MHz for the majority of this test. There is a bit of a bump towards the end, but that may be due to the low battery overlay as this test was unattended until the end.

In addition to the low GPU clocks, we see that the skin temperatures never exceed 34C, which is completely acceptable. This bodes especially well for the internals, which should be much cooler in comparison to previous runs.

Here, we see surprisingly low temperatures. Peak temperatures are around 50C and no higher, with no real chance of throttling. Overall, this seems to bode quite well for Tegra K1, even if the peak temperatures are a bit concerning. After all, Tegra K1 delivers immense amounts of performance when necessary, but manages to sustain low temperatures and long battery life when it it isn’t. More importantly, it’s important to keep in mind that the Kepler GPU in Tegra K1 was designed for desktop and laptop use first. The Maxwell GPU in NVIDIA’s Erista SoC is the first to be designed to target mobile devices first. That’s when things get really interesting.

Microsoft’s Surface Pro 3: Core i3 vs. Core i5 Battery Life

A couple of weeks ago I offered a brief performance preview of the $799 entry level Surface Pro 3 with an Intel Core i3-4020Y. The performance hit in going down to the $799 model is significant but compared to an upgraded ARM tablet you do get substantially more functionality/performance. The big unknown at the time was battery life. Going down to a Y-series part comes with a reduction in TDP (15W down to 11.5W), which could have power implications.

I spent the past week running and re-running battery life tests on the Core i3 model of the Surface Pro 3. For the most part, battery life hasn’t changed. As you’ll see from our laptop results, the Core i3 Surface Pro 3’s battery life shows a slight regression compared to our Core i5 results but not significantly so:

Although our laptop tests didn’t show any gains, our tablet workload showed a substantial increase in battery life for the Core i3 version vs. the Core i5 Surface Pro 3:

An 11% increase in battery life is likely due to the lower power binned Y-series Haswell ULx part. It’s interesting to me that the gains are exclusively in our lightest workload and don’t appear to be present under any of the more active workloads. The decrease in TDP would imply a reduction in peak active power consumption but perhaps that’s more a function of the reduced clocks. What we see at lighter/more idle workloads is a reduction in leakage thanks to the Y-series part.

I still feel like the best overall balance of battery life, storage, performance and price is going to be a Surface Pro 3 equipped with a Core i5. I think where the $799 Core i3 makes sense is if you’re budget limited and left with the choice between a 64GB ARM based tablet or the entry level Surface Pro 3. The problem is typically users who stretch their budget to get a 64GB ARM based tablet want the storage space, which is something you sacrifice when you move to a 64GB Windows 8.1 device (roughly 21GB free on a new install). I don’t see the $799 Surface Pro 3 necessarily catering to the same market as a high end ARM device, but I think the entry level SP3 does embody Microsoft’s mission better than any of the more expensive configurations. There’s very little cross shopping between a $499 ARM based tablet and a $1200+ Surface Pro 3, but the entry level SP3 can serve as an in-between device if you want some of both worlds. 

Short Bytes: NVIDIA’s SHIELD Tablet

Today’s launch of the new SHIELD Tablet with NVIDIA’s Tegra K1 SoC has muddied up the tablet waters a bit. We’ve posted our full coverage of the device, but for those looking for a short summary of the SHIELD Tablet – and whether it’s worth buying or not – here’s the synopsis of NVIDIA’s latest entry into the mobile gaming market.

At its core, the SHIELD Tablet is a fully functional 8″ Android tablet, which is quite a change from the initial SHIELD handheld gaming device. Of course it comes with NVIDIA’s latest Tegra K1 processor, a quad-core ARM Cortex A15r3 CPU with a 192 CUDA core Kepler-derived GPU and 2GB DDR3L-1866. Storage options are currently 16GB or 32GB, and a microSD slot for additional storage. The display is a 1920×1200 IPS panel, and though it has a somewhat limited color gamut it’s a decent if not exceptional display overall. Connectivity consists of 2×2 stream 802.11n WiFi and Bluetooth 4.0, with optional LTE support also available. The 16GB model comes with WiFi only while the 32GB model is equipped with LTE. A capacitive DirectStylus 2 also comes standard on both models.

The overall build quality and design are definitely improved over the Tegra Note 7, with a premium feel that was previously lacking. In many ways, it feels like a larger variant of the Nexus 5, and as an owner of a Nexus 5 that’s pretty high praise. NVIDIA has also provided stereo front-facing speakers that sound better than those in most tablets. The only problem is that the SHIELD Tablet is rather heavy compared to the competition – it weighs 390g, compared to 294g for the Samsung Galaxy Tab S 8.4, but you get better performance with the added weight.

While there’s certainly plenty of hyperbole involved with NVIDIA referring to the K1 as having supercomputing roots, from a pure performance perspective the K1 GPU delivers the goods, topping the charts in most of our graphics benchmarks. The CPU side of the equation isn’t quite as impressive; it’s faster than the previous generation Tegra 4, but given differences in platform, OS, etc. it can be difficult to draw firm conclusions. In general, you can expect somewhere around 5-25% better CPU performance than the Tegra 4, and the K1 tops most of the CPU charts and is at worst competitive with other leading SoCs. About the only potential weaknesses are in the NAND performance (random write is a bit low), and battery life takes a step back from the earlier SHIELD (though that’s with a smaller battery) – and under heavy gaming workloads it can be less than three hours depending on the game. That’s sort of the price you pay if you want maximum gaming performance from a tablet, though: battery life is going to take a hit when running full tilt.

NVIDIA has put quite a bit of effort into the software side of things as well. Besides all the usual Android tablet features – which basically work as expected – you get ShadowPlay support (record and/or stream your gaming sessions), GameStream (either local or remote is in beta), and access to GRID gaming as well. We’ve covered all of these previously, and there’s nothing really new to add: they all work and offer features that you can’t find on other tablets. If you’re in the market for a tablet that can function as a portable gaming system, your options are quite limited.

The base price for the SHIELD Tablet is actually quite good, all things considered: $299 will get you one of the fastest Android tablets around, but don’t forget the accessories. There’s the DirectStylus 2, SHIELD wireless controller, and SHIELD Tablet cover. While you get a DirectStylus 2 with every SHIELD Tablet (a replacement stylus will set you back $20), the wireless controller is a $60 accessory and the magnetic cover is another $40 accessory. The cover isn’t strictly necessary, but as someone that has used quite a few tablets without covers, over time getting some sort of cover is highly recommended, and the SHIELD Cover is a high quality cover that meshes well with the tablet. The wireless controller is a different matter: if you’re looking at this as a gaming device, it’s basically a required accessory. There are many Android games that are designed for a touchscreen, but if you want to use GameStream or play any of the games optimized for a gaming controller, you’ll need the SHIELD wireless controller.

Taken as a complete package, then, you’re looking at $400 for the 16GB WiFi model with accessories and $500 for the 32GB LTE model. You can argue that’s too much, and I wouldn’t necessarily disagree, but if you like the idea of a portable gaming tablet you don’t really have many other choices. You can get the older NVIDIA SHIELD for $200, but that’s half the price for basically half the performance and it was never really that useful except as a gaming device. The SHIELD Tablet on the other hand can function perfectly well as a tablet, and you only need to bring out the controller for times when you want to play games.

Ultimately, the SHIELD Tablet is a far more versatile solution than the original SHIELD, and if you’re in the market for a new tablet it’s still worth considering even if you don’t care much about the gaming aspects – you can always add the controller at a later date. It might be a bit heavy compared to other options, but the performance and features definitely help set it apart. Unless you’re particularly committed to a specific vendor for your devices, the SHIELD makes for a good addition to the Android family.

Gallery: Short Bytes: NVIDIA’s SHIELD Tablet