Build tool/BIOSReleaseEvent
From MSX Game Library
Build tool option BIOSReleaseEvent is used to add a callback function to be called just before BIOS is switched out from page 0. This applies to target formats that place the ROM on page 0 (ROM_48K_ISR, ROM_64K_ISR, ROM_NEO8, and ROM_NEO16), as well as ROM formats that place RAM on page 0 (via the InstallRAMISR option).