INT 19h/18h

INT 19h  Bootstrap Loader Service
http://vitaly_filatov.tripod.com/ng/asm/asm_001.12.html

INT 18h  BASIC Loader Service
http://vitaly_filatov.tripod.com/ng/asm/asm_001.11.html

其他參考資料
int18和int19的区别
BIOS interrupt call
小華的部落格
Option ROM (Wiki)
BIOS boot specification