Thunderbolt Bandwidth Boost is one of the new features offered by Thunderbolt 5 over previous generations of Thunderbolt. At a glance, it dynamically changes the Thunderbolt connection to accommodate additional monitors as well as monitors at higher resolution and refresh rates.
How it works
By default, a Thunderbolt 5 connection has 2 data lanes on each side of the connection, upstream and downstream. Each lane supports up to 40Gb/s of bandwidth, meaning that Thunderbolt 5 supports a symmetrical bandwidth connection of up to 80Gb/s.

When additional video bandwidth is needed, whether that’s from 3 or 4 monitors being connected at once or from multiple high resolution or refresh rate monitors, the Thunderbolt 5 connection can dynamically engage Thunderbolt Bandwidth Boost. Thunderbolt Bandwidth Boost flips the flow of traffic to one of the downstream lanes, allowing for up to 120Gb/s of bandwidth downstream, and 40Gb/s upstream.

Check out our YouTube video on this topic for a visual guide on how Thunderbolt Bandwidth Boost works: