Posted on 2018-03-22
Raspberry Pi 3 Model B+ Benchmarks, Review, and Comparison
Raspberry Pi 3 Model B+ is the newest offering from the Raspberry Pi Foundation sharing much of the same features as the Raspberry Pi 3 Model B with small but significant improvements on many fronts while maintaining the same price. Below is some highlights.
- Increased CPU clock speed from 1.2GHz to 1.4GHz
- Increased memory throughput
- Integrated Heat Spreader (IHS) for SoC
- Integrated MxL7704 PMIC for power management and delivery
- Modularized WiFi/BT Radio with 5GHz and improved performance
- Gigabit Ethernet (albeit still over USB 2.0)
- Ethernet headers for PoE addon
We ran a comprehensive set of benchmarks on the new model, old model, and our boards to compare performance and power consumption.
We begin with heavily optimized C applications like C-Ray and SciMark2. Raspberry Pi 3 Model B+ is still utilizing 32-bit kernel and userland like its predecessor. Raspbian, the official OS of Raspberry Pi, has not moved to 64-bit ARMv8 despite the ARM Cortex-A53 CPU cores supporting it. Legacy 32-bit can help performance for this specific benchmark since some data structures and pointers are smaller than in 64-bit ARMv8 mode. Performance increases around 20% from the Model B, which means that the Raspberry Pi 3 Model B+ matches the performance of similarly clocked ROC-RK3328-CC. It is still slightly behind the AML-S905X-CC since that is about 100MHz faster.
Now we move onto server based workloads. Redis is a good test of overall system performance as it stresses not just the CPU but also the interrupt and memory subsystems. We see the Raspberry Pi 3 Model B+ improving greatly in performance over the previous Model B but still not enough to catch up with modern 28nm SoCs with faster DDR3/4 running ARMv8 kernel and userland.
Java benefits heavily from having native 64-bit arithmetic and performs signficantly faster on the boards running true 64-bit OSes. Despite nearly a 30% increase in performance, the Raspberry Pi 3 Model B+ is left behind.
Sysbench results should be taken with a grain of salt when comparing different binaries but this demonstrates the necessity of true 64-bit ARMv8 kernel and userland. Even with the performance gains, Raspberry Pi products are still held back by 32-bit ARMv7 Raspbian OS. Both the Renegade and Le Potato boards deliver more than 10x the performance.
Raspberry Pi 3 Model B+ uses a newly revised BCM2837B0. There are four limiting features of this SoC just like the previous BCM2837 in the Model B. First, it is missing ARM ISA's Crypto Extensions. For encryption and decryption workloads such as VPN, SSL, SSH, and HTTPS, it's NEON accelerated implementation is roughly 15x slower. This is one of the critical missing features that make the Raspberry Pi 3 Model B+ a poor choice for server based workloads that depend on these security instructions.
The second limiting feature has to do with the GPU which is a 30-bit design limited to 512MB of RAM. It only supports DDR2 so we haven't seen the Raspberry Pi move to faster memory like LP/DDR3 like on Le Potato or LP/DDR4 on Renegade. As a result, memory intensive workloads will be much slower although the Model B+ is marginally faster than the Model B.
Like the previous Model B, the Model B+ has not implemented UHS support for MicroSD cards. It is still limited to 25MB/s while other boards are more than twice as fast.
As mentioned by Eben Upton, the Raspberry Pi 3 Model B+ has a single USB 2.0 channel which is shared between the ethernet and four port USB hub. Despite having a physical gigabit ethernet, performance is limited to 320Mb/s (40MB/s) peak. If you are using a USB hard drive serving files over ethernet, the effective throughput is reduced to 160Mb/s (20MB/s). Intensive NAS based use-cases for the Pi continues to be ruled out. ROC-RK3328-CC (Renegade) has both dedicated Gigabit Ethernet and dedicated USB 3.0 so it can deliver an order of magnitude more throughput.
The most horrifying aspect of the Raspberry Pi 3 Model B+ is the power consumption. They've learned the wrong lesson from ASUS Tinker Board, Orange Pi, et al. While the new PMIC addressed the voltage drop issues, power consumption shot up 50% for marginal increases in performance. In our previous guess of the Raspberry Pi Foundation's plans, we assumed Broadcom would help make a power efficient Cortex-A35 design. Instead, BCM2837B0 went in the exact opposite direction.
In our CPU burn tests, the board consumed nearly 1.8A without any peripheral or screen connected. This is at the borderline of the MicroUSB power spec and will un-doubted create new power related headaches for many end-users. Most cell phone power supplies simply will not work for this board.
It would be fair to say that the Raspberry Pi 3 Model B+ will not be winning any performance per watt benchmarks especially compared to the super fast and efficient Le Potato board. However, it is a significant step in the right direction compared to its predecessor. The hardware designers have addressed quite a few long-standing issues and we expect the next generation Raspberry Pi 4 to further amortize design issues.
- The new integrated heat spreader (IHS) will allow the Raspberry Pi 3 Model B+ to sustain performance for longer and perform more reliably than the previous Model B. It will help the temperature sensor adequately throttle performance when a specific area of the chip becomes too hot and extend the useful life of the board specially in industrial conditions.
- The new WiFi/Bluetooth module performs with excellence. It also uses a module design which saves companies from having to go through expensive radio certification process. In our tests, the WiFi performance on the 5GHz band exceeded performance of the Model B on the 2.4GHz band by five times.
- The power delivery and management IC has eliminated the voltage drop across the previous poorly-designed power delivery circuit that was causing power warnings with compliant power supplies. While the added power consumption exacerbates the problem, we still feel that this is a step in the right direction.
You can find all of the performance data that we aggregated on this Google Sheet.