Cable Matters 20Gbps USB C Switch supports a maximum resolution of 4K@60hz when connected to a Thunderbolt 3 monitor.
Applies to
Protocol Differences
While USB4 and Thunderbolt 3 share some underlying technology, such as the USB-C connector, they are not fully interchangeable. Thunderbolt 3 supports advanced features like daisy-chaining, PCIe tunneling, and higher data transfer speeds of up to 40Gbps, all of which are enabled by the Thunderbolt 3 protocol. USB4 20Gbps, on the other hand, is a variant of the USB4 standard that maxes out at 20Gbps and does not inherently support the Thunderbolt 3 protocol.
Bandwidth Limitations
Thunderbolt 3 offers a maximum bandwidth of 40Gbps, necessary to drive certain high-performance monitors, especially those with higher resolutions or refresh rates (such as 4K@120Hz or 5K displays). The Cable Matters USB4 20Gbps switch, however, only supports a bandwidth of up to 20Gbps. This reduced bandwidth is insufficient to support the full capabilities of a Thunderbolt 3 monitor, which is why the connection is "downgraded" to a USB-C connection.
Downgrade to USB-C Alt Mode
Without native Thunderbolt 3 support, the switch defaults to USB-C DisplayPort Alt Mode. In this mode, video data is transmitted over USB-C but is limited to the available bandwidth (20Gbps), which supports a maximum resolution of 4K@60Hz. This is still sufficient for many applications but falls short of the higher resolution and refresh rates that Thunderbolt 3 monitors can support when connected to a true Thunderbolt 3 source.
Compatibility
While USB4 is designed to be backward compatible with older standards like USB 3.2 and DisplayPort, the specific USB4 20Gbps implementation in this switch lacks compatibility with the Thunderbolt 3 protocol, meaning it can't offer full Thunderbolt 3 functionality. The absence of this protocol results in limited display and data capabilities when connected to a Thunderbolt 3 monitor.
Cable Matters is currently developing a 40Gbps USB-C switch that is expected to offer full Thunderbolt 3 support, providing enhanced compatibility for all USB-C devices. This upgrade will allow users to take advantage of higher data transfer speeds and improved video performance with USB-C monitors and peripherals.
