The MagPi, Issue 88

The MagPi Issue 88The latest issue of The MagPi Magazine includes a whopping 12-page feature investigating the thermal performance of the Raspberry Pi 4 Model B single-board computer as it is affected by a series of firmware updates released since its launch earlier this year.

When I reviewed the Raspberry Pi 4 at launch, I highlighted its dramatically increased power draw and heat output compared with its predecessor the Raspberry Pi 3 Model B+. In the months since, the Raspberry Pi Foundation has been working to address the issue through a series of firmware updates – and, with assistance from Eben Upton and Tim Gover, my feature runs through each release and sees what difference it actually makes.

For the feature, I had to develop a method of benchmarking the Raspberry Pi. Power draw was relatively straightforward: the built-in current meter in a bench-top power supply is used to measure the minimal draw at idle and peak draw at load. For thermal performance, I wrote a custom benchmark which uses two open-source utilities – glxgears and stress-ng – to place a heavy load on both the CPU and the GPU while measuring the resulting temperature rise and the speed of the CPU, which throttles at 80°C to protect the silicon.

These measurements provided a graph of temperature rise and fall, the latter thanks to a five-minute cool-down period built into the benchmark, but for a more visual approach I also took thermal imagery of the board at idle and load to demonstrate which components are responsible for the heat output and better highlight the improvements made at each firmware revision. This was no small undertaking: the benchmarking and thermal imagery was completed for five firmware revisions, the last of which was not publicly available at the time of testing, plus a baseline Raspberry Pi 3B+ for comparison.

The feature also takes a look at a real-world workload, in which temperature and clock speed is measured while a four-worker compile of the Linux kernel is carried out. This revealed something which may come as a surprise to critics of the board: Using the latest firmware, the Raspberry Pi 4 did not throttle at all during the compilation – something that can’t be said for the Raspberry Pi 3B+, which throttled to 1.2GHz from 1.4GHz almost immediately. For the final bit of testing, there’s even a comparison of the Raspberry Pi 4 running sat flat on a desk and balanced vertically – at Upton’s suggestion – with a resulting dramatic impact on the throttle point and operating temperature.

Finally, firmware developer Tim Gover was kind enough to answer my questions on what the Raspberry Pi 4 firmware actually does, how it is developed, and how it can have such a dramatic impact on power usage – along with the confirmation that USB mass-storage booting and IPv6 network booting are on the to-do list for future releases.

The full feature, and plenty more beside, can be found at your local newsagent, supermarket, or downloaded at no cost in digital form under a Creative Commons licence from the official website.

Raspberry Pi Geek, Issue 09-10/2019

Raspberry Pi Geek Issue 09-10/2019The launch of the new Raspberry Pi 4 single-board computer brought with it, as usual, my detailed analysis over on Medium. The post has drawn considerable interest, in particular the benchmarking and thermal imagery aspects. German publisher Computec got in touch shortly after publication to ask if they could licence the post for translation and republication in the local enthusiast magazine Raspberry Pi Geek – and that issue is on shelves now.

Effectively a blow-by-blow recreation of the Medium post, translated and reformatted for the confines of a paper magazine, the seven-page feature walks through what’s new in the design, carries out numerous benchmark tests from synthetic and real-world performance workloads to power draw and – as has become a signature of mine – high-quality thermal imagery showing just where the extra power demanded by the Raspberry Pi 4 is going on the board.

Each benchmark includes a graph for easy at-a-glance performance comparisons between the new model and every version back to the original launch Model B. High-quality photography of the board and its various components are also featured, and have translated particularly well to the page.

Raspberry Pi Geek Issue 09-10/2019 is on shelves now in Germany, and is also available from Computec’s online outlet.

The MagPi, Issue 76

The MagPi Issue 76There’s no missing my contribution to this month’s The MagPi: it’s plastered all over the cover. The launch of the Raspberry Pi 3 Model A+ ends a four-year absence of the compact form factor from the Raspberry Pi line-up, and there’s no better way to celebrate its launch than with a massive cover feature.

The spread begins with a two-page introduction dominated by imagery of the board, before moving on to a plan view which calls out the individual components that make up the board – including the single USB port, BCM2387B0 system-on-chip (SoC), and the radio which, for the first time in a Model A variant, adds WiFi networking and Bluetooth connectivity. Each part includes macro photography, all taken in my in-house studio.

The next section of the feature runs through a series of benchmarks which, in-keeping with previous launches I’ve covered, compares the Pi 3A+ with other mainstream Pi models going all the way back to the original Raspberry Pi Model B. The feature also includes a look at the size and weight, the first time I’ve used that particular metric, along with comparative thermal imagery showing how the smaller surface area of the PCB copes with running the same high-performance processor as the larger Pi 3B+ – again, all captured in-house.

Finally, the cover feature closes with a two-way interview I conducted with project co-founder Eben Upton and principal hardware engineer Roger Thornton. In it, Eben confirms that the Pi 3A+ represents “tidying up ‘classic’ Raspberry Pi,” and that the Raspberry Pi 4 – still very much on the drawing board – will launch a whole new era for the low-cost single-board computer family.

The launch issue is available now from your nearest newsagent or supermarket in print, or can be downloaded free of charge under a Creative Commons licence from the official website.