Geoff Chappell - Software Analyst
The HAL started out in numerous variants, many not written by Microsoft, though presumbly all written with the help of some special kit for HAL development. The variety got ever thinner. The last known non-Microsoft HAL is from version 5.2 and x64 Windows only ever had the one HAL. By version 6.3, even the interface of exported functions was apparently mature. No exports are added to the HAL for Windows 8.1. Indeed, the HAL then goes most of a decade with no new exports, the next addition being for the 2004 release of Windows 10.
Though version 6.3 has no new exports, it does remove one. The age-old HalSetTimeIncrement, first exported from version 3.50, is no longer a HAL export as of version 6.3. It seems never to have been documented, anyway.