Raspberry Pi Zero 2 W Review — Hands-on with the Fastest Zero Ever
Boasting a move to a similar CPU as the Raspberry Pi 3 A+/B+, clocked down to 1GHz, the new Zero 2 W packs a lot of punch for its size.
It's taken a while, but the engineers at Raspberry Pi have finally shown the compact Zero form factor some love: Meet the Raspberry Pi Zero 2 W, which takes the heart of a Raspberry Pi 3 and crams it into a tiny board with lots of potential.
Launched today at just $15, the new quad-core single-board computer is a drop-in replacement for its predecessor — but just what is Raspberry Pi offering for the extra cash, and does it deliver value for money compared to the $5 Raspberry Pi Zero and $10 Raspberry Pi Zero W?
Let's put it through its paces and find out.
The hardware
- Price: $15
- CPU: Broadcom BCM2710A1 (BCM2837) (4× 1GHz Cortex-A53)
- GPU: Broadcom VideoCore IV
- RAM: 512MB LPDDR2
- Storage: MicroSD (not included)
- Networking: 2.4GHz 802.11b/g/n Wi-Fi, Bluetooth 4.2
- Ports: Mini-HDMI, Micro-USB 2.0 OTG, Camera Serial Interface (CSI), 40-pin GPIO header
- Dimensions: 65×30mm (around 2.56×1.18in)
The Raspberry Pi Zero 2 W brings with it a surprise: The second product to come out of the company's in-house application-specific integrated circuit (ASIC) team, after the launch of the RP2040 microcontroller earlier this year. This time around the team has integrated two third-party dice — the BCM2710A1 die, originally found inside the Broadcom BCM2837A1 system-on-chip that powered the Raspberry Pi 3 Model A and B, and a 512MB LPDDR2 die — into a single package, solving the no-room-for-RAM problem that had prevented a refresh of the Zero form factor earlier.
It echoes the package-on-package design of the early Raspberry Pi models, including the Raspberry Pi Zero range, where the memory chip was literally attached to the top of the SoC — but this time everything is integrated into a single package taking up barely more footprint on the board than the package-sandwich that powered its predecessor.
Aside from its novel packaging, the BCM2710A1 is functionally equivalent to the die found on the Raspberry Pi 3 Model A+ and B+ — bar a performance drop, which sees the clock speed reduced to 1GHz. The reason: thermals. With far less PCB to sink heat into, the Zero would have trouble keeping its cool at higher clock speeds — though if you add a heatsink or fan there's nothing stopping you overclocking the chip to Raspberry Pi 3 levels and beyond.
One definite disappointment is the radio module. While it's great to see a fully-enclosed pre-qualified module replace the exposed silicon chip of the original Zero, the Synaptics BCM43436/8 used is limited to 2.4GHz networks and Bluetooth 4.2 — but corners had to be cut somewhere to hit that oh-so-tempting $15 launch price.
Elsewhere, things are identical to the original Zero. You've still got a compact Camera Serial Interface (CSI) to one side, microSD to the other, micro-USB ports for power and USB 2.0 On-The-Go (OTG), and a mini-HDMI for video and audio. The 40-pin general-purpose input/output (GPIO) header is present and correct, but the smaller RUN and TV headers have been removed and replaced by test pads on the rear of the board.
Power and thermals
Moving from an outdated single-core chip to a considerably more powerful quad-core part can't help but have an impact on how power-hungry the Raspberry Pi Zero 2 W gets — everything comes at a cost, after all. Impressively, though, the spike in power is nowhere near as bad as you might fear.
The idle power draw, measured at the Raspberry Pi OS desktop with HDMI, a USB wireless keyboard and mouse receiver, and Wi-Fi connected to mimic a common setup, is barely any higher than a Raspberry Pi Zero — the same, in fact, to two significant figures. Put the board under load and the two drift apart: The Raspberry Pi Zero 2 W hit a peak of nearly 3W under the test workload, to the Zero's 1.7W.
Putting the Raspberry Pi Zero 2 W under a thermal camera, after treating for thermal emissivity, it's clear where that power's going — and, interestingly, where in that clever twin-dice package you'll find the four CPU cores. Under a thermal stress test the board gets uncomfortably hot, reaching over 72°C (around 162°F) at its hottest point after ten minutes.
That's not enough to make the chip throttle itself, with the Zero 2 W completing the 10-minute stress test at its full clock speed. That's only true for an uncased board in free air; if you're looking to put a heavily-loaded Zero 2 W in an enclosed casing, even the official case from Raspberry Pi itself, you're going to want to add some form of aftermarket cooling to keep performance high.
Performance
Not all of that extra power is wasted as heat: Some goes to boosting performance, and depending on your workload you can expect dramatic improvements from switching to the Raspberry Pi Zero 2 W.
A file compression benchmark offers a quick look at raw CPU performance. The Zero 2 W completes the test in less than half the time of its predecessor, and switching to a multithreaded compression program to take advantage of those four CPU cores widens the gap still further.
For anyone working with webcams or other video footage, the good news continues: Video transcoding is now possible, at least if you're happy to drop the resolution or frame rate down a bit, with the Zero 2 W hitting an average of 19 frames per second using the hardware H.264 encoder via v4l2 when encoding a 1080p video — compared to the original Zero's paltry 1.2 FPS. To get over 30 FPS at that resolution, though, still requires a Raspberry Pi 4.
Another real-world test, the Tesseract benchmark performs optical character recognition over a series of magazine scans. To process 10 high-resolution pages took the original Zero over 40 minutes; the Zero 2 W managed it in just over five.
Not all workloads will play nicely with just 512MB of RAM. The image editing test runs a high-resolution file through The GIMP, and while the Zero 2 W's time of 233 seconds was an improvement on the Zero's 396 seconds both are easily beaten by the Raspberry Pi 3 Model B+ at 78 seconds — thanks almost entirely to its more capacious 1GB of RAM.
There's a key field in which the Raspberry Pi Zero 2 truly pulls away from its predecessor: Machine learning, particularly computer vision tasks. While the original Zero is powerful enough for smaller networks, it lacked the grunt to perform object detection and segmentation tasks on video — something that can't be said of its successor. Although 1.71 frames per second from the SSDLite-MobileNet-v2 network is low, it's good enough for a range of scenarios — and at a very low power draw to boot.
The Zero 2 W is also surprisingly usable as a general-purpose desktop — just about, at least. Its performance in the Speedometer 2.0 browser benchmark, carried out in Chromium, is six times higher than the original Zero, though nearly a third that of a Raspberry Pi 4. Open more than a couple of tabs, however, and that 512MB of memory all-but guarantees you a visit from the out-of-memory killer.
For games and emulation, the Zero 2 W shines given its low cost and light power requirements. In an OpenArena timedemo benchmark at 720p, the original Zero failed to reach a frame rate that could be rounded up into a whole number — but the Zero 2 W averaged 28 frames per second, a figure that can be boosted north of 30 by decreasing the resolution or changing the detail settings.
The Wi-Fi radio, sadly, disappoints. The lack of support for 5GHz networks limits maximum throughput, and even its 2.4GHz performance fails to match that of the Raspberry Pi 3 or 4 — although it did easily beat the original Zero, managing 43.5Mbps to its predecessor's 24.4Mbps.
Conclusion
At just $5 more than the Raspberry Pi Zero W, the Zero 2 W is incredible value. Its performance is leagues apart from its single-core predecessor, and opens up entirely new workloads like video transcoding and on-device computer vision — while idling at roughly the same power draw, ideal for bursty battery-based builds.
It's not necessarily going to be a drop-in replacement for every project, however. Loaded power draw is higher, and the excess heat could cause problems for tight cases without much ventilation. It's also a shame that it doesn't use the same radio as the Raspberry Pi 4, and that a bottleneck somewhere along the line throttles its throughput.
That 512MB of RAM is limiting, too, and it wouldn't be a shock to see a mid-stream refresh in a year or so bump it up to a more reasonable 1GB. It's also directly responsible for a recommendation not to run a 64-bit operating system on the board: While the CPU is more than capable, the higher memory requirements will see you hitting an out-of-memory condition that much sooner.
These, though, are niggles. It's hard to imagine many scenarios where saving $5 by using a Raspberry Pi Zero W instead of the new Zero 2 W would be worth it — assuming you can pick one up, of course.
The ongoing component shortages, already responsible for a $10 price hike on the Raspberry Pi 4 Model B 2GB, mean that demand is likely to outstrip supply on this one, so anyone interested is advised to pick theirs up via the official website sooner rather than later.