Now that the Amazon Fire TV Cube has been released, a lot of people will be deciding between it and the less expensive Fire TV 3 pendant. While they look very different on the outside, thanks to the Fire TV Cube’s hands-free Alexa capabilities, they’re very similar on the inside. They both have the same video playback capabilities, which include 4K @ 60FPS and HDR support. That’s because they both have the exact same 1.5Ghz quad-core CPU, the same Mali-450 MP3 GPU, and the same 2GB of RAM. With identical chips, you’d expect them to perform the same on benchmarks, but it turns out the Fire TV Cube is faster than the Fire TV 3. However, there’s an important catch that throws things off.

For this benchmark comparison, I’m focusing on only the Fire TV Cube and Fire TV 3, since their specs are so similar. I hope to compare these two devices to the Fire TV Stick and past Fire TV models in a future article. Even though the Fire TV Cube and the Fire TV 3 use the exact same chips, my theory, and the reason for running these benchmarks, was that the Fire TV Cube’s larger size would allow for better cooling and, therefore, result in slightly better performance.

Remember, benchmark scores that push devices to their limits do not translate well into real-world performance, since you’ll rarely be pushing these devices this hard, but it’s still an interesting exercise. Even though the Fire TV Cube is slightly faster, you’re not going to see a difference in day-to-day use between it and the Fire TV 3, especially when it comes to watching videos.

I started off by running GFXBench’s suite of GPU tests. This is a good measure of each device’s gaming capabilities. Right off the bat, you can see that the Fire TV Cube scored 601 frames on the offscreen 1080p T-Rex test, while the Fire TV 3 scored 570 frames. A 5% higher score might not seem like much, but it’s fairly significant and a much bigger difference than I was expecting, considering these two devices have the exact same CPU and GPU.

Next, I ran the 3DMark Icestorm benchmark. This mostly tests the GPU but also measures the CPU’s performance using a physics test at the end of the benchmark. The score of 4,173 for the Fire TV Cube and 4,069 is an average of several GPU tests plus the one CPU test. At about 3% higher, this benchmark confirms that the Fire TV Cube does have a slight advantage over the Fire TV 3, as far as raw power goes.

Taking a look at 3DMark’s benchmark chart reveals exactly why the Fire TV Cube is scoring higher than the Fire TV 3. This chart shows CPU clock speed, CPU usage, and FPS values throughout the benchmark test. As you can see, the CPU clock speed (blue line) for the Fire TV Cube is locked to its full 1.5Ghz speed the entire time, while the Fire TV 3’s CPU clock speed is fluctuating drastically during the test.

Investigating further reveals that the Fire TV Cube’s CPU governor is set to “Performance” mode, while the Fire TV 3’s CPU governor is set to “Interactive” mode. The CPU governor configuration of a device is what determines how the operating system scales the frequency of the CPU. Performance mode means the CPU frequency is set to a specific value and will never change, so the Fire TV Cube always runs at 1.5Ghz, regardless of whether the CPU is being used or sitting idle. Interactive mode means the CPU frequency dynamically scales in response to the workload placed on the CPU. When the Fire TV 3 is idle, it lowers the CPU frequency and ramps it up when needed.

The Fire TV 3’s less than ideal CPU governor configuration is likely due to heat management. By keeping the CPU frequency low when it’s not in use, the Fire TV 3 will produce less heat. Since it is in a smaller package, there’s probably less room to dissipate heat, so it’s a bigger concern than with the Fire TV Cube, which probably has better overall cooling. Even though ramping up the CPU frequency on the Fire TV 3 happens nearly instantaneously, the tiny delay is likely why the Fire TV Cube performs better in these benchmarks.

After determining why the Fire TV Cube’s GPU benchmark scores outperform the Fire TV 3’s scores, I moved on to run benchmarks that focus only on the CPU. To my surprise, the Fire TV 3 does notably better when it comes to CPU benchmarks. In GFXBench’s Driver Overhead test, which taxes the CPU, the Fire TV 3 scored 2,614 frames compared to the Fire TV Cube’s score of 2,468. I expected to see similar results for the CPU tests as the GPU tests from early, but instead, there’s about a 6% drop with the Fire TV Cube.

Running the PCMark benchmark confirms the results seen with GFXBench. PCMark stresses the CPU by running various productivity tasks like photo editing and data manipulation. It’s not very relevant to Fire TV usage, but the Fire TV Cube’s score of 2,692 and the Fire TV 3’s score of 2,890 shows the same 6% drop for the newer Fire TV model.

After re-running all the benchmarks and re-examining the 3Dmark charts from above, I finally noticed the cause of the unexpected CPU performance drop with the Fire TV Cube. Looking at the CPU usage lines (purple) in the 3DMark charts, you can see that both devices go to around 100% CPU usage during the physics portion of the benchmark. This is expected, since that test stresses the CPU, but when looking at the CPU usage during the GPU tests you can see the Fire TV Cube’s CPU usage is notably higher than the Fire TV 3’s CPU usage.

I enabled the System X-Ray utility to view the CPU usage in real-time and noticed that one of the 4 cores on the Fire TV Cube was always at around 50% usage while idle. All 3 other cores on the Fire TV Cube, as well as all 4 cores on the Fire TV 3, hover around 25% usage while idle.

Checking the list of running processes on the Fire TV Cube revealed the culprit to be a package called “amazon.speech.wakewordservice,” which I assume is what the Fire TV Cube uses to detect the Alexa wake word. This means that the Fire TV Cube uses approximately 6% of its processing power (25% of one CPU core) to listen for hands-free commands. That 6% extra load correlates perfectly with the 6% lower CPU benchmark scores.

While the Fire TV Cube is capable of performing better than the Fire TV 3, despite having identical hardware, thanks to its better CPU governor and heat dissipation, you’ll only see those advantages when utilizing the GPU because it needs to use about 6% of its CPU for its hands-free Alexa feature. That overhead is obviously not found on the Fire TV 3 or any other Fire TV device. For those wondering, no, muting the microphones does not clear up that 6% usage. I wouldn’t expect it to since the Fire TV Cube still needs to be ready to respond instantly the moment you unmute its mics.

Ultimately, these benchmark scores aren’t different enough in either direction to translate into real-world benefits or handicaps for either the Fire TV Cube or the Fire TV 3, and so shouldn’t really be considered when making a buying decision.

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