diff options
| -rw-r--r-- | src/Boot/Windows/BootSector.asm | 31 |
1 files changed, 16 insertions, 15 deletions
diff --git a/src/Boot/Windows/BootSector.asm b/src/Boot/Windows/BootSector.asm index 33674146..351b2c67 100644 --- a/src/Boot/Windows/BootSector.asm +++ b/src/Boot/Windows/BootSector.asm @@ -43,23 +43,24 @@ main: call print skip_loader_name_msg: - ; Determine boot loader segment - mov ax, TC_BOOT_LOADER_SEGMENT - - ; Check available memory - cmp word ptr [ds:413h], TC_BOOT_LOADER_SEGMENT / 1024 * 16 + TC_BOOT_MEMORY_REQUIRED - jge memory_ok - - mov ax, TC_BOOT_LOADER_SEGMENT_LOW - - cmp word ptr [ds:413h], TC_BOOT_LOADER_SEGMENT_LOW / 1024 * 16 + TC_BOOT_MEMORY_REQUIRED - jge memory_ok - - ; Insufficient memory - mov ax, TC_BOOT_LOADER_LOWMEM_SEGMENT + ; Determine boot loader segment + mov ax, word ptr [ds:413h] ;available kB from BIOS + sub ax, TC_BOOT_MEMORY_REQUIRED ;minus TC_BOOT_MEMORY_REQUIRED + jc mem_toolow + and ax, 0FFE0h ;32K align + shl ax, 6 ;convert kB to segment addr (*1024/16) + cmp ax, 8000h + jb mem_toolow ;we can't load below 8000h + cmp ax, TC_BOOT_LOADER_SEGMENT + jbe memory_ok ;don't load above TC_BOOT_LOADER_SEGMENT (9000h) + mov ax, TC_BOOT_LOADER_SEGMENT + jmp memory_ok + +mem_toolow: + mov ax, TC_BOOT_LOADER_LOWMEM_SEGMENT memory_ok: - mov es, ax + mov es, ax ; Clear BSS section xor al, al |