So today, if you want an eGPU or a super-speedy Thunderbolt 3 storage drive, your choice of computer is very limited. Thunderbolt 3 is also more expensive to implement than standard USB, because it’s not an open standard and it requires an extra chip. Because Thunderbolt is an Intel standard, you won’t find it on any AMD-powered computer. Though there are a number of Thunderbolt 3 eGPUs out there, few laptops and desktops come with Thunderbolt 3 and almost no motherboards support Thunderbolt 3 out of the box. That’s good news for everyone, especially laptop users who want to play games by connecting an eGPU (external graphics card). Intel made news when it said it had given the Thunderbolt 3 protocol to USB Promoter Group, allowing devices with USB 4 ports to potentially be compatible with Thunderbolt 3 devices and USB 4 devices to attach to Thunderbolt 3. (Image credit: Shutterstock / Schuchrat Kurbanov) Compatible With Thunderbolt 3 Optionally If you do connect to, for example, a Type-A, 5 Gbps USB 3 port by using an adapter, the speed and power will drop down to the lowest common denominator. That’s no surprise, as other recent standards such as USB Power Delivery only work on Type-C. Don’t expect to see a USB 4 device or hub with old-fashioned Type-A ports. This almost goes without saying: USB 4 will only operate over the Type-C connector. So, if the video only needs 20 percent of the bandwidth to drive your 1080p monitor that’s also a hub, the other 80 percent will be free for transferring files from your external SSD which can operate over either USB protocol or PCIe. Better Resource Allocation for Video, PCIe: In lieu of alternative mode where the other interface takes over the connection, USB 4 devices can use a process called 'protocol tunneling' that sends DisplayPort, PCIe and USB packets at the same time while allocating bandwidth accordingly.

Compatible with Thunderbolt 3 devices: Some, but not necessarily all USB 4 implementations will also work with Thunderbolt 3 devices.

DisplayPort 2.0 can use up to 80 Gbps, which is double the amount available to USB data, because it sends all the data in one direction (to the monitor) and can thus use all eight data lanes at once. DisplayPort 2.0 can support 8K resolution at 60 Hz with HDR10 color.

DisplayPort Alt Mode 2.0: USB 4 supports DisplayPort 2.0 over its alternative mode.

The data is transmitted in two sets of four bidirectional lanes.

40 Gbps Maximum Speed: By using two-lane cables, devices are able to operate at up to 40 Gbps, the same speed as Thunderbolt 3.

Thunderbolt usb 4 to hdmi