Choosing an Embedded Motherboard or Single Board Computer

With fanless embedded PCs being in the market for a long time now you may be familiar with different heatsink designs to keep the system cool enough under load. Higher performance computers require larger heatsinks with fins to maximise the surface area and spread the heat accordingly, this is known as passive convection cooling.

Embedded SBC with Heatsink

Heatsinks are also adopted by single board computers and industrial motherboards to spread the heat generated by the CPU and keep them cool enough to operate accordingly without having to throttle. Other components onboard might also require some assistance in passive cooling if generating large amounts of heat, such as video capture cards and even some new high-speed NVMe SSDs.

Heatsinks still require enough surrounding air or a degree of airflow to move generated heat from building up too much. If for example you placed a single board computer with heatsink inside a compact enclosure, all components inside the enclosure that are generating heat will cause the ambient temperature inside the enclosure to rise, in turn replicating the same problem you were trying to avoid in the first place. This heat needs to be spread as best as possible to the outside of the chassis or enclosure, similar to how fanless box PCs operate.

Embedded Board with Heatspreader

Heat spreaders are mated to the exterior surfaces. Through conduction, the aluminium heat spreader dissipates heat evenly to the surface of which it is bonded to. Embedded Computers rely on heat spreaders to dissipate heat from the CPU to the heatsink as part of the systems chassis. Heat spreaders are typically available with most Embedded Single Board Computers and can be easily designed and manufactured for bespoke use cases.

Designed to be embedded as part of a larger subsystem, whether inside a system chassis or control cabinet, airflow is either greatly limited or completely restricted for fanless operation. Factors such as heat generation from board level components such as CPUs and GPUs can cause the temperature inside the chassis or cabinet to rise much greater than the ambient temperature outside the chassis or cabinet. For this reason, an increased temperature tolerance should be considered on the upper band of supported operating temperatures. If your factory floor has an ambient temperature of 50°C, you should not consider a solution supporting operating temperatures of 50°C as being suitable if embedding a computer into a cabinet, particularly a high-performance power-hungry platform. A common wide temperature board will support 70°C which will give you the extra tolerance you require.

Manging colder environment extremes are much more manageable and the only consideration should be for cold start-ups. This means the computer will boot from the lowest possible temperature and not just ‘continue to operate’ after start-up should the temperature drop during system operation. A common wide temperature board will support -20°C and will guarantee cold system start-up in an ambient temperature of -20°C.

Energy efficiency is one of the key primary benefits when choosing single board computing. It is important to benchmark your application when integrating a new Embedded PC as it helps gauge a system’s ability to run applications reliably. Comparing benchmark CPU scores will allow you to benefit from lower power CPUs without sacrificing on adequate performance for the application.

CPUs are built on either RISC or CISC architecture. Arm Single Board Computers are RISC (Reduced Instruction Set Computing) based, and Intel x86 Single Board Computers are CISC (Complex Instruction Set Computing) based. Comparatively, x86 Computing offers many more instruction sets which in turn leads to better performance at an offset of more power consumption.

In modern day computing, the lines between RISC and CISC are a little more complex as both ARM and Intel adopt ideas from one another. Multi-core processors are now developed on architecture variations from one another.

Industrial boards are connected to a wide range of sensors, IIoT devices, peripherals, displays etc. The source of your data, peripherals, and available bus types will typically define your projects required I/O and ultimately the required footprint for an embedded computer. Depending on the space you have available to integrate an industrial board, you may have to compromise on the type of connector available on board. It is important to check the datasheets and confirming the connector type available for all required ports along with the supported technology to guarantee it also carries enough bandwidth.

You may be familiar with an I/O plate as it is standard on larger format PCBs such as industrial motherboards. Embedded single board computers also adopt standard I/O plates but also include various onboard connectors. In some cases, daughter boards are also required for breaking out additional connectivity with high density connectors, this is common as part of a PC/104 stack. The smaller the SBC, the number of ports available for the most common connectors such as DB9 for Serial, Type A or Type C USB, or even RJ45 for Ethernet will be reduced.

When utilising board level connectors, it is worth noting the additional measures required when fixing your bill of materials. A custom cable assembly will have to be engineered by either yourself or your SBC distributor. As this creates added complexity it can increase your projects timescale to deployment and create additional unforeseen lead times on the continued rollout.

Some installations for single board computers and industrial motherboards are completely headless, meaning they don’t require a display output to carry out the designated tasks when deployed in the field. Other use cases require the embedded computer to be paired with a display, or in some use cases multiple displays. Where standard I/O plate display connectors such as VGA, DVI, DisplayPort and HDMI are relatively straight forward connections, they also take up a lot of retail space on board, particularly if requiring multi-display capabilities. Another limitation to the standard display outputs is the capability for interfacing with a TFT LCD panel display which use embedded display connectors. TFT LCD panel displays are a common choice for machine builders or OEM product design and manufacturers for complete control over custom aesthetics and continued reduction in overall cost of build.

A standard TFT LCD display panel commonly utilise embedded display connections such as LVDS (Low Voltage Differential Signalling) or eDP (Embedded Display Port). Since its introduction in the 1990s, LVDS has been the de facto standard for video input from most of the major TFT LCD manufacturers. The newest standard, eDP, carries some advantages for OEMs over LVDS being a fully digital interface and is now commonly being supported by the latest industrial SBCs to market. Benefits of the modern eDP standard includes a much higher signal bandwidth allowing for higher resolutions and higher refresh rates whilst supporting a lower power consumption. Cable assemblies are also simplified with eDP vs LVDS as they require a significantly reduced number of high-speed wire pairs for any given link rate.

Much like checking the datasheet for I/O connector types and supported interfaces, the same applies for small form factor expansion such as mPCIe and Next Generation Form Factor M.2 standards. Connector types can be shared between the desired expansion card and host motherboard whilst the supported Bus technology differs, making it incompatible.

A common example of this is for mPCIe expansion. Although this is transitioning to be a legacy expansion,  mPCIe is still common for connectivity expansion cards such as Wi-Fi and Cellular, these mPCIe slots can also be used for storage in the form of mSATA SSDs. Whereas Wi-Fi or Cellular would utilise PCIe or USB signals from the mPCIe expansion slot, an mSATA SSD would require SATA signals to be supported. The latest available small form factor M.2 expansion is a little more complex with its available card form factors, keys and Bus support but carries distinct advantages in its compact footprint including support for higher bandwidths simply by utilising more PCIe lanes. Here is an in-depth article about available slots, keys and supported Bus standards via M.2 expansion.