AI-assisted driver brings Thunderbolt 4 support to Windows 98 SE and other legacy systems

Developer Yeo Kheng Meng has released xHCI98 v3.0.0.0, an experimental driver that enables support for USB4 and Thunderbolt 3/4 on legacy Microsoft operating systems. According to a report by Tom's Hardware, the driver allows Windows 98 SE, Windows Me, Windows 2000, Windows XP, Windows Vista, and Windows 7 to utilize modern xHCI host controllers. This development provides functional connectivity for USB 3.x, USB4, and Thunderbolt 3/4 devices on systems that previously lacked native driver support for these high-speed interfaces.

The release addresses a specific hardware limitation found in mid-2010s PCs that feature xHCI-only chipsets without legacy EHCI controllers. Meng explains that without xHCI support, basic peripherals like keyboards, mice, and flash drives rely on BIOS legacy support and cannot be hotplugged. Furthermore, Ethernet and audio devices often fail to function entirely on these systems. The new driver fills this gap by replacing Windows’ own USB port and hub drivers, facilitating the connection of USB 1.1, 2.0, and SuperSpeed devices.

Technical Scope and AI Development

The xHCI98 project extends beyond simple USB storage support. It includes a second driver, xhciuas.sys, to handle UAS (USB Attached SCSI) storage, and a third driver, xhcicm.sys, for Thunderbolt 3 and USB4 docks and NVMe enclosures. Meng developed and tested the software primarily on Intel hardware, specifically a 2020 ThinkPad P14s Gen 1 with a Comet Lake xHCI controller. He acknowledges that this is a solo project heavily assisted by AI, noting that bugs are not unexpected even on identical hardware.

Meng utilized Claude Fable 5.1 for planning, Claude Opus 5.5 for coding, and Codex GPT 6 Astra as an adversarial reviewer. A demo video shows various USB devices being hotplugged into the test ThinkPad, demonstrating the driver's ability to manage connections without crashing. While the test rig is not exhaustive, the driver demonstrates practical utility for connecting modern peripherals to legacy operating systems that lack native xHCI capabilities.

Affected Systems and Users

This release primarily targets retrocomputing enthusiasts and users of older operating systems who wish to use modern hardware. It is particularly relevant for users of PCs from the mid-2010s that have xHCI-only chipsets. These systems often struggle with legacy operating systems because they lack the necessary EHCI controllers for USB 2.0 compatibility. The driver allows these users to bypass BIOS limitations and use modern USB devices, including docks and NVMe enclosures, on Windows 98 SE through Windows 7.

Meng warns that users should expect bugs due to the experimental nature of the project and its reliance on AI assistance. The developer has provided an extensive blog post detailing compatibility, creation, and usage instructions. Users are advised to review these materials carefully before deploying the driver on critical systems. The project remains a niche solution for specific hardware and software combinations rather than a general-purpose fix for all legacy systems.

What should you do?

Users interested in this driver should verify their hardware compatibility, specifically checking for xHCI-only chipsets and the absence of legacy EHCI controllers. They should review the developer’s blog post for detailed usage instructions and known limitations. Testing should be conducted on non-critical systems to identify potential instability or bugs. Users should monitor for future updates as the developer continues to refine the software based on community feedback and testing results.

What to do and how to stay safe: Windows 98

• Verify that your hardware has an xHCI-only chipset and no legacy EHCI controller before attempting installation.
• Review the developer’s blog post for compatibility details and known bugs specific to your Windows version.
• Test the driver on a non-critical system to assess stability and functionality with your specific USB devices.
• Monitor the project’s GitHub page for updates and bug fixes as the developer continues to refine the software.

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Frequently asked questions

Which operating systems are supported by the xHCI98 driver?

The driver supports Windows 98 SE, Windows Me, Windows 2000, Windows XP, Windows Vista, and Windows 7.

What AI tools were used to develop the driver?

The developer used Claude Fable 5.1 for planning, Claude Opus 5.5 for coding, and Codex GPT 6 Astra for adversarial review.

Does the driver support hotplugging of USB devices?

Yes, the driver facilitates hotplugging for USB 1.1, 2.0, and SuperSpeed devices, which previously required BIOS legacy support.