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Raspberry Pi 3 Model B vs. 3 Model B+

What's in a plus? A side-by-side comparison of the latest Pi and its predecessor.

In this post we take a first look at the new Raspberry Pi 3 Model B+ and some of the new and improved features, along with the indication that there are more details yet to be revealed.

Please note that we were using pre-launch versions of the board and operating system, so it’s likely that certain things will become a little clearer from launch onwards.

At first glance

The very first thing you notice when you set eyes on a Pi 3 B+ is that that the system-on-chip (SoC) is different, or at least it uses visibly different packaging to the 3B. On closer inspection, we see that this is marked BCM2837 and so it would appear to be fundamentally the same Broadcom SoC as employed by its predecessor. So what about the packaging change? With metal being a better conductor of heat could this perhaps hint at a performance improvement? Let&rrsquo;s see!

Speaking of metal, there’s an interesting addition in the form of a logo stamped screening can and the wireless IC from the underside of the board has gone, or at least moved, suggesting at minimum improvements to EMC compliance and possibly even a new wireless device. Also the chip antenna has disappeared and been replaced with the PCB antenna design as used on the Zero W.

The wired network connectivity also appears to have benefited from an upgrade, with the LAN9514 integrated 4-port USB 2.0 hub and 10/100 Ethernet IC having been swapped out for a LAN7515, which integrates a 6-port USB 2.0 hub (4x usable) with 10/100/1000 Ethernet. While USB 2.0 does have a theoretical max transfer speed of 480 Mbit/s, additional features of this device include:

  • 802.3az Energy Efficient Ethernet
  • Jumbo frames up to 9KB
  • Multiple automatic power saving modes

All of which should certainly benefit network-centric applications. For example, jumbo frame support will be welcomed by those seeking that bit extra network performance, e.g. when using network attached storage (NAS) with the Pi as a server or as a client.

Wait a minute, what’s that — a new 4-pin header marked “PoE”!

Power-over-Ethernet

Typical PoE usage.

Power-over-Ethernet (PoE) is a term used to describe both standardised and ad-hoc systems that pass power along with data on twisted pair cabling, finding popular use in powering VoIP desk phones and remote CCTV cameras, for example. Standards IEEE 802.3af (PoE) and 802.3at (PoE+) are able to provide up to 15.4W and 25.5W respectively to each connected powered device (PD).

PoE network switches, together with “power injectors” that can be used with more basic switches, are used to provide the power source. To give an example, the Netgear GS308P (121-8132) pictured above provides four ports, each capable of supplying 15.4W, plus four non-powered ports.

Standards compliant systems are able to cope with the DC supply being inverted by crossover cables, with the powered device and power sourcing equipment (PSE) implementing mechanisms to indicate the class of PoE supported and to remove power if non-compliant equipment is detected.

In short, PoE provides an incredibly convenient way of delivering power to remote network devices that in some cases may be located up to 100M away from the switch. At the time of writing it’s not clear precisely what PoE capabilities the Pi 3 Model B+ will benefit from, although 802.3af with 15.4W would be more than sufficient for the Pi plus a HAT and most standard peripherals.

Digging deeper

So let’s now take a look at the hardware as seen from the operating system, or rather an early version of this that was supplied with the pre-launch boards.

If we start by running lsusb and above we can see the output on the Pi 3 Model B+, showing that the LAN7515 presents two hub controllers, compared with one on the Pi 3B as shown below.

Next if we run lscpu.

This is the same as we get on a Pi 3 Model B — apart from the CPU max MHz is 1400 instead of 1200! That’s right, up to 1.4GHz without overclocking.

And if we look at CPU info via the proc filesystem with:

pi@3bplus:~ $ cat /proc/cpuinfo

We can ignore the hardware value as this is an indicator of SoC family rather than specific model, but the revision we are interested in.

This time we get a020d3, which is different to what we get with the Pi 3 Model B.

And unsurprisingly the new revision number is not detailed anywhere publicly at the time of writing, which along with the new packaging and max CPU speed would suggest that we really do have a new variant of the Broadcom SoC.

Using ethtool we could query the network driver and confirm that the LAN interface does indeed support 1000BaseT as a media type.

We couldn’t check out the wireless in more detail as this wasn’t detected by the O/S using the supplied pre-launch image, but this would seem to suggest that it is in fact a new device.

Basic benchmarking

We can use sysbench to run a simple CPU benchmark and time how long it takes to verify prime numbers.

$ sysbench --test=cpu --num-threads=4 --cpu-max-prime=9999 run

Here we can see that the B completed the task in around 35s, while the B+ did this in 30s, which is about a 15% speed-up and corresponds nicely with the clock speed increase.

Since actual CPU MHz is dynamically scaled according to load, we can check the current speed by running in a second terminal window:

$ watch -n 1 cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_cur_freq

Doing this on both systems confirmed that the Pi 3 Model B ramped up from idling at 600MHz to 1.2GHz, while the new B+ went from 600MHz to 1.4GHz.

This is sufficient to satisfy our curiosity and there will no doubt be others publishing much more detail benchmarking reports and analysis as hardware becomes generally available.

Initial thoughts

Performance increases are always welcome and while there are always those in search of that bit extra processing power or network throughput, Power-over-Ethernet is almost certainly the hottest feature with the Raspberry Pi 3 Model B+. It may at first seem like a niche capability, but the benefit of being able to run a device with network and power delivered by a single cable — and without a mess of power supplies and power cables — is not to be underestimated.

Sure, you can buy separate “power splitters” and PoE add-ons for Raspberry Pi, but nothing beats a closely integrated solution and this is a feature that is likely to give birth to many more exciting, fun and eminently practical projects, with neat combined networking and power delivery at their core.

Andrew Back

Open source (hardware and software!) advocate, Treasurer and Director of the Free and Open Source Silicon Foundation, organiser of Wuthering Bytes technology festival and founder of the Open Source Hardware User Group.

16 Mar 2018, 15:32

Comments

March 29, 2018 20:20

Great article. Just from the packaging box I believe the wireless was upgraded as well, I see 802.11 AC listed now, and possibly the bluetooth, which shows at 4.2

[Comment was deleted]

March 14, 2018 10:47

It might be an interesting article - IF it was displaying in English, not an Eastern typescript. E.g. "用の「パワースプリッタ」"
Reading on Firefox 59.0 (64 bit).

0 Votes