Picking the right system-on-module can make or break your device’s power budget, thermal envelope, and unit economics. It’s a crucial decision when building your connected device, IoT gateway, or home automation product.
Product teams often default to the Raspberry Pi Compute Module 4 or the new CM5. But those boards can be overkill, adding watts, heat, and cost you may not need.
Below we pit the Onion Omega2S against RPi CM4/CM5 across 12 categories – power, size, firmware workflow, BoM, and more – to see which SoM wins where. Let’s see how they stack up.
Results at a Glance
Click on the comparison category to see more details
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Raspberry Pi Compute Modules |
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Processing Power
| Device | CPU | Memory | Storage |
|---|---|---|---|
|
Omega2S |
580MHz MIPS |
64 to 128 MB |
16 to 32 MB NOR Flash |
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RPi CM4 |
1.5 GHz quad-core Arm Cortex-A72 |
1 to 8 GB |
0GB, 8GB, 16GB or 32GB eMMC |
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RPi CM5 |
2.4GHz quad-core Arm Cortex-A76 |
2 to 8 GB |
0GB, 16GB, 32GB or 64GB eMMC |
Omega2S
- CPU: single MIPS core targeting efficiency
- Memory: 64 to 128 MB
- Storage: 16 to 32 MB of reliable NOR flash
Raspberry Pi Compute Module
- CPU: Multi-core ARM processors
- Memory: 1 to 8GB
- Storage: 0-64 GB eMMC
Verdict:
Raspberry Pi Compute Modules have more compute horsepower, featuring multi-core processors and gigabytes of memory.
Display Output
Omega2S
- Linux-based framebuffer support
- Drive small screens over SPI
Raspberry Pi Compute Module
- Support HDMI and DSI for HD video putput
Verdict:
Raspberry Pi Compute Modules support High Definition video output and are a better choice for use cases that require video output.
Size
Omega2S
- Dimensions: 34 x 20 x 2.8 mm
- Area: 680mm2
Raspberry Pi Compute Module
- Dimensions: 55 × 40 x 4.7
- Area: 2200 mm2
Verdict:
Omega2S modules are much smaller, almost a quarter of the size of a Raspberry Pi Compute Module, and a better choice for space-constrained use-cases.
Need a sample board?
The Omega2S Eval Board offers a streamlined starting point for working with the surface-mount Onion Omega2 modules. Built to reduce setup friction, they are essential tools for evaluation, prototyping, and development.
Heat & Power Consumption
Omega2S
- Idle: 30.8˚C, 0.66W
- Under load: 36˚C, 1.05W
Raspberry Pi Compute Module
- Idle: 38.9˚C, 2.65W
- Under load: 63.7°C, 6.66W
- Source: Tom’s Hardware RPi CM5 review
- Idle: 2W
- Normal Operation: 7W
- Source: RPi CM4 Datasheet
Verdict:
Omega2S consumes far less power and operates at a much lower temperature, even under load.
Raspberry Pi Compute modules require active cooling for processor intensive tasks.
Module Cost
| Device | MSRP (USD) |
|---|---|
|
Omega2S (OM-O2S) On-Board 64 MB memory, 16 MB storage, WiFi Radio |
$16.84 |
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Omega2S+ (OM-O2SP) On-Board 128 MB memory, 32 MB storage, WiFi Radio |
$20 |
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Raspberry Pi Compute Module 4 1GB RAM, 8GB storage, WiFi + Bluetooth variant |
$40 |
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Raspberry Pi Compute Module 5 2GB RAM, 16GB storage, WiFi + Bluetooth variant |
$55 |
Omega2S
- Price per module hovers at around half of a Raspberry Pi compute module
- Two variants to choose from depending on memory and storage needs
Raspberry Pi Compute Module
- Prices shown for lowest spec RAM and eMMC storage variant
- Variants without wireless (WiFi and Bluetooth) cost less
- Variants with more RAM or more eMMC storage cost more
Verdict:
Omega2S modules are cost half (or less) than Raspberry Pi Compute Mdoules
Customizing Firmware
Omega2S
- Firmware is based on OpenWRT and can be customized with the OpenWRT build system
- Custom software can be packaged and compiled as an OpenWRT software package and included in a custom firmware image
- New tooling for building packages and custom firmware images is available from Onion, significantly cutting down on compilation time.
Raspberry Pi Compute Module
- Custom software must be packaged and compiled as a Debian software package in order to be included in a custom OS image
- Several tools are available to create OS images: pi-gen, rpi-imager, rpi-image-gen
- The pi-gen tool is recommended in the Compute Module documentation. However a new rpi-image-gen tool was launched in March of 2025.
Verdict:
The Omega2S provides a repeatable and documented method for creating customized software packages and firmware images.
The Raspberry Pi ecosystem has several methods for customizing the OS. Users must dig into each tool to find out the strengths and weaknesses.
Firmware Flashing during Production
Omega2S
- Firmware images must be flashed to the onboard storage during production. There are a few methods to do this.
- The recommended method is to use the bootloader, the serial command line and an ethernet connection
- This method requires a host computer and a carrier board that exposes the soft reset pin, UART0, and the Ethernet Port
Raspberry Pi Compute Module
- OS images must be flashed to the CM eMMC using a host computer and the RPi USB slave port. There are a few methods to do this.
- The rpiboot utility requires a host computer and a carrier board that exposes the RPi USB slave port and jumper pins
Verdict:
Flashing firmware to both the Omega2S and RPi Compute Modules requires a host computer and access to specific interfaces/pins on the carrier board.
Storage Reliability
Omega2S
Pros:
- High life span (20 years of data retention, 100,000 erase/program cycles)
- less prone to data corruption
- Slower reads and writes
- Lower storage density
- The Overlay filesystem used on the Omega2S makes it resistant to data corruption caused by flash wear and sudden power loss
Raspberry Pi Compute Module
Pros:
- High density
- Faster reads and writes
- More prone to data corruption and bad blocks
- Wear out over time
- Lower overall life span (especially in applications with a lot of write operations)
- According to the datasheet, the default operating system expects a graceful shut down before power is disconnected to preserve the file system. This is hard to guarantee in real world use cases.
Verdict:
The storage on the Omega2S is more reliable in most applications because it uses NOR flash and overlayFS. A combination of a very reliable storage medium and a filesystem resistant to data corruption, even with sudden power loss.
Connecting Module to Carrier Board
Omega2S
- Pin Connection: castellated pins for surface mount connection, no additional parts needed
- Securing to Board: soldered down in reflow oven
- Process: Omega2S modules come packaged in reels, pick and place machine handles placement on carrier board before soldering. No manual additional labor.
Raspberry Pi Compute Module
- Pin Connection: uses 2x 100-pin high-density board-to-board connectors, the carrier board must have 2x of these connectors. Incurs additional cost.
- Securing to Board: machine screws should be used to securely fasten the compute module to the carrier board to ensure consistent connection to pins and persistent connection to board. Incurs additional cost.
- Process: Compute Modules are packaged in individual boxes and must be unpacked manually. Attaching the Compute Module to the carrier board cannot be automated and must be done by hand. This increases the labor time and costs for production.
Verdict:
The Omega2S is easier and cheaper to securely connect to a custom carrier board.
Carrier Board Design Complexity
Omega2S
Power supply ✅
- Requires 3.3V/0.4A power supply, low power and affordable.
- Relatively straight-forward regulator circuit to step down 5V from USB
- Can use readily available 5W power supplies
Wireless Antenna
- Rated for 2dBi antenna for WiFi
- Choice of using u.FL antenna, an SMT chip antenna, or a PCB trace antenna
High speed circuits ✅
- USB2.0 host pins needs impedance matched data lines
Raspberry Pi Compute Module
Power supply
- CM5 requires 5V/5A power supply
- CM4 requires 5V/3A power supply
- More costly power supplies to supply high current
Wireless antenna ✅
- Choose between onboard antenna or connect external antenna to u.FL connector
High speed circuits
- CM5: USB3.0, DSI/CSI, HDMI require careful circuit layout to function properly
- CM4: DSI/CSI, HDMI require careful circuit layout to function properly
Verdict:
The design for an Omega2S carrier board is much simpler than for the Raspberry Pi
Carrier Board BoM Cost
Note: Cost comparison excludes power supply circuit, PCB cost, and application specific connectors or ICs. Meant to offer guidance for comparison.
| Omega2S | Omega2S+ | Raspberry Pi CM4 | Raspberry Pi CM5 | |
|---|---|---|---|---|
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Module |
$16.84 |
$20 |
$40 |
$55 |
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WiFi Antenna |
$0.13-$0.30 |
$0.13-$0.30 |
$0 Using onboard antenna |
$0 Using onboard antenna |
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Board-to-Board connectors |
N/A |
N/A |
$2-$4 |
$2-$5 |
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Passive Heatsink & Mounting Screws |
N/A |
N/A |
N/A |
$5 |
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Mounting Hardware |
N/A |
N/A |
$0.50-$4.50 |
N/A |
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Total |
$16.97 to $17.14 |
$20.13 to $20.30 |
$42.50 to $48.50 |
$62 to $75 |
Omega2S
Required components:
- WiFi antenna since there is no on-board antenna. 2dBi ceramic chip antennas cost $0.13 to $0.30 depending on volume
Raspberry Pi Compute Module
Required components for Raspberry Pi CM4:
- 2x Hirose 100-pin board-to-board connectors: $1-2 each depending on volume
- Mounting hardware: estimating $0.50-$4.50 depending on implementation
Required components for Raspberry Pi CM5:
- 2x Amphenol 100-pin board-to-board connectors: $1-$2.50 each depending on volume
- Official heatsink, includes screws required to mount heatsink and CM onto carrier board: $5
Verdict:
The BoM for an Omega2S Carrier Board costs less than half of a carrier board for the Raspberry Pi CMs
Resources for Carrier Board Design
Omega2S
- Circuit diagrams for several variations of carrier boards available on GitHub
- Hardware design guide available on GitHub
- Omega2S footprint templates available on GitHub for Eagle, Altium Designer, and PADS PCB design software
- No ready-to-go board designs available for PCB design software
Raspberry Pi Compute Module
- Circuit diagram for Compute Module IO board available in datasheet
- No hardware design guide available
- No footprint templates available
- Compute Module IO Board design available for KiCad
Verdict:
Different resources are available for the Omega2S and Raspberry Pi Compute Modules.
How did they stack up?
- If power draw, size, and heat are key constraints, the Omega2S pulls ahead with lower idle draw, a much smaller footprint, and less heat to sink.
- If you need native HDMI and GPU horsepower for full-HD signage or rich UX, the RPi CM4/CM5 still rules that niche despite higher power budgets
- For most headless gateways, sensors, and automation hubs, Omega2S delivers the functionality you need at a fraction of the BoM
| Comparison Category | Omega2S |
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