Connecting two devices over thunderbolt (windows -> mac). If I unplug the cable between them I can’t reconnect until I completely power down my windows PC (and unplug from the wall)

Troubleshooting Thunderbolt Connectivity Between Windows and Mac Devices

Connecting two high-performance devices via Thunderbolt can significantly enhance data transfer speeds and create a seamless workflow. However, establishing and maintaining a stable connection between a Windows PC and a Mac can sometimes present challenges. This article explores a common scenario involving Thunderbolt networking and offers practical troubleshooting strategies.

Scenario Overview

Hardware Configuration:

MacBook Pro (2023, M2 Max): Equipped with three Thunderbolt 4 ports.
Windows Desktop PC: Upgraded with an ASUS ThunderboltEX 4 card, providing two Thunderbolt 4 ports.

Connection Objective:
Establish a Thunderbolt-based network link between the MacBook Pro and the Windows PC.

The Setup and Initial Success

Using the ThunderboltEX 4 card in the Windows PC, the connection has been successfully established and recognized on both ends. The Mac shows up on the PC’s Thunderbolt control panel, indicating a functional link. When active, the network connection operates smoothly, providing rapid data exchange.

The Encountered Issue

Problems arise during disconnection and reconnection attempts:

Detaching the cable: The connection drops successfully.
Reconnecting the cable: The devices do not re-establish communication.
Troubleshooting attempts:
Trying different Thunderbolt cables yields the same results.
Utilizing various port combinations on both devices does not resolve the issue.
Workaround:
Power cycling the Windows PC (completely shutting down and unplugging from power) along with reconnecting the cable restores the connection.

Understanding the Problem

This behavior suggests that the Thunderbolt connection, once disrupted, struggles to reinitialize without a full system power cycle. This could be attributed to factors such as:

Driver or Firmware issues: Thunderbolt controller drivers or firmware may not handle reconnections gracefully.
Cable or port compatibility: While multiple cables and ports were tested, occasional hardware issues can still influence connection stability.
Power management settings: Certain power saving features may interfere with Thunderbolt port functions.
Thunderbolt security or trust settings: These can sometimes affect the recognition of devices after a disconnection.