ASUS ThunderboltEX 4 expansion card: two Thunderbolt 4 ports for ASUS boards

The ASUS ThunderboltEX 4 is a PCIe expansion card that adds two Thunderbolt 4 ports to a desktop PC. It is for people whose motherboard has no Thunderbolt, but who want to connect fast external drives, docks or displays.

What the card provides

The card is built around an Intel JHL 8540 Thunderbolt 4 controller. It carries two USB Type-C ports that support Thunderbolt 4 and USB4, each with up to 40 Gb/s of bidirectional bandwidth, according to ASUS. It also has two mini DisplayPort input connectors that follow the DisplayPort 1.4 specification.

Why the DisplayPort inputs matter

Thunderbolt carries video as well as data. A desktop's graphics card produces the picture, so the card needs a way to receive that signal. You connect the graphics card's output to the ThunderboltEX 4's mini DisplayPort inputs with cables, and the card passes the video out through the Type-C ports. ASUS describes this as redirecting video signals through the card, with DisplayPort 1.4 support for monitors up to 8K.

In practice, this means one Type-C cable can run a Thunderbolt display and also carry data to its built-in ports.

Daisy-chaining

ASUS says each port can connect up to five Thunderbolt-enabled devices in a daisy chain using Thunderbolt cables. A chain might run from the PC to a dock, then a drive, then a display. Total bandwidth is shared along the chain, so several demanding devices on one port will each get less than the full 40 Gb/s.

Charging

The listing mentions quick charging of up to 100W. This is power delivery to a connected device such as a laptop or phone. ASUS adds that actual charging performance can vary in real-world conditions, and the power drawn depends on the device and the cable.

Compatibility is the big point

The listing states that the card only supports ASUS motherboards. Thunderbolt add-in cards generally connect to the motherboard through a dedicated header, as well as through the PCIe slot, and the board's firmware must support the card. That is why it is limited to specific boards. The motherboard's manual and the ASUS support page list which boards work, and which slot and header to use.

Size

The listing gives dimensions of about 9.1 x 7.3 x 2.4 inches (23 x 18.5 x 6 cm), which probably includes packaging and the bracket. Check the case for a free PCIe slot and the layout for the cable to the motherboard header.

Who it suits

It suits owners of a compatible ASUS board who work with Thunderbolt audio interfaces, fast external storage, docks or high-resolution displays, and who would rather add the ports than replace the board.

What to check before you buy

• Board support: confirm your exact ASUS motherboard model is listed as compatible.
• Slot and header: check which PCIe slot to use and where the header is on the board.
• Graphics output: make sure your graphics card has an output that can be linked to the mini DisplayPort inputs, and that you have the cables.
• Your devices: check that your drives, docks and displays use Thunderbolt or USB4 Type-C.
• Cables: use cables rated for Thunderbolt if you want the full 40 Gb/s.
• Charging needs: check the power your device needs against the 100W figure.

The short version

• A PCIe card adding two Thunderbolt 4 / USB4 Type-C ports with an Intel JHL 8540 controller.
• Up to 40 Gb/s per port, daisy-chaining of up to five devices and up to 100W charging, as ASUS states.
• Two mini DisplayPort 1.4 inputs carry video from your graphics card.
• Listed as working only with ASUS motherboards.

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