Retrocomputing developer Yeo Kheng Meng has released xHCI98 v3.0.0.0, an experimental driver that brings USB 3.x, USB4, and Thunderbolt 3/4 support to Windows 98 SE, ME, 2000, XP, Vista, and 7. The driver allows modern host controllers to work with these older operating systems, which lack native xHCI support.
Meng created the project for users of mid-2010s PCs with xHCI-only chipsets and no legacy EHCI controller. Without xHCI support, keyboards, mice, and flash drives rely on BIOS legacy support, cannot be hotplugged, and devices such as Ethernet and audio do not work. The driver replaces Windows' own USB port and hub drivers and adds separate drivers for UAS storage and Thunderbolt/USB4 docks and NVMe enclosures.
The driver is a solo effort with heavy AI assistance, and Meng warns that bugs are not unexpected. It has been developed and tested mostly on Intel hardware, specifically a 2020 ThinkPad P14s Gen 1, so users with different hardware should proceed with caution. The release notes also cover standby and hibernation caveats, installation methods, and tuning options.