IC technology has progressed over the years to allow manufacturers to incorporate several subsystems on a single die that already contains a single or multi-core processor. Computer and communications companies have driven this trend for the last several decades to produce all-in-one and embedded packages that are, or are close to, an entire computer or electronic system on a chip. SoCs, SiPs, and CoMs can be found in everything from smartphones to automated systems, and their applications are endless. While they may look the same and offer similar functionality at their roots, SoCs, SiPs, and CoMs are different in several aspects. The purpose of this article is to explain those differences and provide an overview of their key technologies.
A System-on-a-Chip (SoC) integrates all the necessary components needed for a system on a single chip or integrated circuit (IC). This includes one or more processor cores (single, dual, quad, octo, etc.), a GPU, memory (RAM/ROM) or memory subsystems (memory controllers), onboard storage (Flash, eMMC), and I/O subsystems (PCIe, SATA, USB, SPI, I2C, UART). Communications technologies can also be incorporated into the chip, such as Ethernet, Wi-Fi, Bluetooth, and RF.
Think of them in contrast to a typical PC motherboard, where components (CPU, GPU, memory, etc.) are separated based on function but connect through a centralized interfacing circuit board; imagine that these components were instead designed into the board itself. Where an SoC has all the components placed on a single circuit die, a motherboard connects those pieces of hardware as discrete components or as add-in cards and modules.
By placing all of the components of an SoC on a single chip (Figure 1), manufacturing costs are lower, performance is increased, and power consumption is reduced. The downside is that, unlike a full-sized computer, they are locked into their design configuration with no upgrade path. It also means that any component failure is chip-wide, meaning the other components in the signal chain fail as well, or their functionality is severely impaired. SoCs also offers a small footprint that allows them to be integrated into mobile devices, autonomous vehicles, UAVs, robotics, medical devices, and more.
Figure 1: System on a Chip ( )
An SiP (System-in-a-Package) is similar to an SoC, but instead of incorporating all the components on a single die, SiPs feature several ICs that are enclosed in one or more chip-carrier packages (their own separate dies) that can be stacked for increased functionality. This means that RAM, storage, I/Os, and other components are stacked vertically or horizontally on a single substrate. They are then connected using fine wire or solder bumps, and then bonded to the package (PCB).
Generally, SiPs are produced using several different technology types – module (single or multichip), a stacked die, or a 3D package. Modules are the standard package, incorporating one or more horizontal component dies with chip-level interconnects. Stacked packages place those dies in a vertical orientation with chip-level interconnects, allowing more components to be incorporated in a confined space. Finally, a 3D package provides a combination of pre-packaged devices and components that are stacked vertically with package-level interconnects.
Manufacturing SiPs using the stacked method means that few external components are needed to make the package function, making it easier to integrate into compact and complex systems, and it also simplifies PCB layouts. SiPs (Figure 2) are widely used in smartphones, MP3 players, IoT devices, and wearables, including smartwatches. As with any technology, SiPs do have a drawback in terms of manufacturing, as any defective chip in the stack will render the entire unit non-functional, even if the others work correctly.
(Figure 2: System-in-a-Package ( )
A CoM (Computer-on-Module) is a step above an SoC, and is placed between a full-on computer and a microcontroller when it comes to performance and functionality. By definition, CoMs are complete embedded computers built on a single PCB, which are similar to SoCs and SBCs in that they host a microprocessor, RAM, and I/O controllers, but they rely on a carrier board for all other input/output peripherals to be connected. This provides CoMs with an advantage over the others in this list, in that the carrier board can be upgraded with the latest CoM (Figure 3) when they become available.
Another advantage of using a carrier board is that they can also be outfitted with FPGAs, which can port functions to the CoM or carrier board for increased performance. Being able to upgrade the processor without needing to redesign the carrier board can save costs, development times, and the ability to develop both hardware and software simultaneously. The modular aspect of CoM design is also useful for manufacturers making a line of scaled products, providing the ability to swap out some parts of the system, enabling different levels of functionality between an entry-level product and a feature-packed high-end model. Each level of the product could also have its own set of peripherals that could be swapped out as new upgrades become available, making them cost-effective in both the short and long term.
Figure 3: Computer-on-Module ( )
The differences between SoCs, SiPs, and CoMs are minimal, and yet each has its advantages and disadvantages over the others, which boils down to functionality and application types. While SiPs and SoCs can be used for compact and embedded solutions, such as smartphones and wearables, CoMs have an upgrade path and can be utilized as full-blown computers to some extent.
Differences Between SoCs, SiPs, and CoMs
|Integrates all components on a single die||Components are stacked and interconnected||Essentially a full-blown PC|
|Can contain analog, digital, and wireless technologies||Can contain any number of integrated ICs for increased functionality||Rely on an add-in module and a carrier board to function|
|Offers higher performance and reduced power consumption||Can be stacked vertically or horizontally, maximizing space||Can be easily upgraded or have components replaced if failure occurs|
|Almost always includes native input/output subsystems||SiP design can be simplified, keeping costs low||Can include additional processors, such as FPGAs|
|Provides reduced latency between components||Fewer components are needed to make the platform function||Saves on development costs and production times|
|Manufacturing costs are low||Dominates the mobile industry due to its small footprint||Can be scaled to include additional functionalities if required|
- CoM: Computer-on-Module
- eMMC: embedded Multi-Media Controller
- Flash: Data storage technology based on programmable memory
- GPU: Graphics Processing Unit
- I2C: Inter-Integrated Circuit
- IC: Integrated Circuit
- I/O: Input/Output
- PC: Personal Computer
- PCIe: Peripheral Component Interconnect express
- RAM: Random Access Memory
- ROM: Read-Only Memory
- SATA: Serial AT Attachment
- SBC: Single Board Computer
- SiP: System-in-a-Package
- SoC: System-on-a-Chip
- SPI: Serial Peripheral Interface
- UART: Universal Asynchronous Receiver/Transmitter
- UAV: Unmanned Aerial Vehicle
- USB: Universal Serial Bus