[lDOS] Device driver call to int 15h function 4100h should initialise BL

Title	[lDOS] Device driver call to int 15h function 4100h should initialise BL
Author	E. C. Masloch
Created	2026-06-08 20:42:51 +0200 Jun Mon
State	closed

lDOS would call the "WAIT ON AN EXTERNAL EVENT" ROM-BIOS functions without initialising the BL or BH registers.

Reference: https://github.com/LoopZ/TheList/blob/fa803c25/source/Interrupt%20List/INT%2015%20SYSTEM%20FUNCTIONS/INT%201541%20SYSTEM%20WAIT%20ON%20EXTERNAL%20EVENT%20CONVERTIBLE%20and%20some%20others.txt

E. C. Masloch on 2026-06-08 20:45:45 +0200 Jun Mon

Fixed in hg 05df7843dbe2 on 2025-12-15. Note that there was already a commented out instruction that would also initialise BL to zero, indicated with a comment reading "NO TIMEOUT".