Waveshare PCIE TO 4-CH Gigabit/2.5G ETH Board (B) is a 4-port Gigabit or 2.5 Gbps Ethernet board designed for the Raspberry Pi 5. This board connects four RJ45 ports to the Pi’s 16-pin PCIe interface and also includes a mounting option for the Pi5 Connector Adapter (C). The only limiting factor is the Pi’s PCIe Gen2/Gen3 x1 interface, as the 2.5GbE ports share the available bandwidth and cannot operate at full speed simultaneously.
The Gigabit Ethernet variant features Realtek RTL8153 USB to Ethernet controllers, while the 2.5GbE variant relies on RTL8156 controllers, and both integrate a VL805 PCIe to USB bridge chip. The board also includes status LEDs for link and activity indication, and draws power directly from the PCIe interface without requiring an external power supply. The device is plug-and-play and supports Raspberry Pi OS out of the box with no additional drivers required. Applications include routers, firewalls, network test systems, and multi-interface edge or lab setups built around the Raspberry Pi 5.
PCIE TO 4-CH Gigabit/2.5G ETH Board (B) specifications:
- Compatibility – Designed for Raspberry Pi 5, but should work with other SBCs with a compatible 16-bit PCIe FFC connector
- Host Interface – 16-pin PCIe FFC connector for interfacing with the Raspberry Pi 5 via a VL805 PCIe to 4x USB 3.0 host controller chipset
- Ethernet
- 4x Gigabit Ethernet via RTL8153 chips (PCIE TO 4-CH Gigabit ETH Board (B) variant)
- 4x 2.5 Gbps Ethernet via RTL8156 chips (PCIE TO 4-CH 2.5G ETH Board (B) variant)
- Misc
- Mounting option for Pi5 Connector Adapter to add full HDMI ports and M.2 PCIe socket
- Green LED – link status
- Yellow LED – activity status
- Power Supply – 5V via PCIe cable (no external power input required)
- Dimensions – 91.5 x 85 mm
- Operating Temperature – -40°C to +80°C
The expansion board is all well and good, but as mentioned earlier, the main limiting factor is the Pi 5’s PCIe Gen2 x1 interface, which officially supports up to 5.0 GT/s of bandwidth (around 4 Gbps usable). Unofficially, PCIe Gen3 x1 can be enabled to increase bandwidth to up to 8 GT/s, but as this bandwidth is shared between the four ports, not all Ethernet interfaces can be used at full speed simultaneously, although three 2.5GbE ports may be used at almost full throughput.
The 4-Port Ethernet board is plug-and-play, so no specialized software is required for Raspberry Pi OS, Ubuntu, OpenWrt, and other operating systems. At the time of writing, the Wiki is still under development. We had seen other 2-port Raspberry Pi 5 or CM5 routers with the likes of Supernetworks’ “Secure Programmable Router”, Radxa Dual 2.5G Router HAT, and Waveshare’s own CM5-DUAL-ETH-MINI-BOX, but 4-port solutions are harder to find, and so far, we only covered Mcuzone’s CM5 5G Router expansion board with 4+1 Gigabit Ethernet ports.
The PCIE TO 4-CH Gigabit/2.5G ETH Board (B) is available on Aliexpress for $42.29/$53.09 and on Amazon for $55.99/$66.99. You can also check out the Waveshare store for additional purchase options starting at $39.99, but Waveshare’s pricing does not include shipping. The board will ship with PCB standoffs, screws, and a 16-pin 40 mm PCIe cable.
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> 5.0 Gbps of bandwidth (around 4 Gbps usable). Unofficially, PCIe Gen3 x1 can be enabled to increase bandwidth to up to 8 Gbps
With PCIe these 5 and 8 numbers are not Gbps but GT/s (gigatransfers per second). With Gen2 speeds the rather inefficient 8b/10b coding is used (‘wasting’ 2 signals out of 10 as such resulting in 5 GT/s -> 4 Gbps) while at Gen3 speeds and above 128b/130b coding is used only ‘wasting’ 2 signals out of 130 and as such resulting in almost twice the speed compared to 8b/10b: 8 GT/s -> ~7.88 Gbps.
And that’s not even counting the PCIe headers (12-16 bytes) for each data frame, where many mother boards are limited to 128..512 bytes of payload per frame. At 12 bytes per 128 that an extra 10% bandwidth loss! As a rule of thumb, counting on 80% ratio for Gen3 and above generally leads to roughly accurate estimates, i.e. 6.4 Gbps for Gen3x1
And, then, instead of using a PCI-E switch they put a USB controller which puts yet another layer of protocol overhead on top to make the communicaiton even more inefficient. Not to mention the USB bus being unidirectional which both the PCI-E and ethernet interfaces are bidirectional.
It doesn’t help that the VL805 is PCI-E v2.0 so it’s got 4Gb/s of TX + 4Gb/s of RX to the RPI (minus PCI-E protocol overhead). Four 2.5Gb/s ethernet ports would give 10Gb/s of TX and 10Gb/s of RX. Which is quite larger than the link to the RPI. For the 4x 1Gb/s board, the mismatch is pretty small and would probably be not an issue. But four 2.5Gb/s ports? One could run at full speed, but not two and certainly not all four.
The board might as well just use a simpler single port 5Gb/s ethernet PCI-E controller linked directly to a switch chip with 4 ports of their choosing. That would be two chips instead of 5 that they’re using. Plus lower power consumption, the option to make it route/switch, etc. with no RPI overhead.
Very true
[ maybe few expect the 2.5Gbps being saturated all the time, so it’s maybe just pragmatically not for plugging in/out that often and having data burst potential for 2.5G and maybe already being prepared for a Pi6 hw, then having higher bandwidth(?), but considering an USD39-67 for a mostly 4×1.5Gbps (bundled or shared, about (almost) the price for external 8x1G/5×2.5G/8×2.5G or 4×2.5G/2x10G switches on a high demand 12V/1A power budget) with headroom for 2.5Gbps bursts, me agreeing with all previous comments. (thx) ]