Maybe clear direction flag first? cld
?? On Mon, 1 Aug 2022 at 08:40, Pascal <[email protected]> wrote: > hi, > > I have a live system with only UEFI boot supported. > > to indicate this to users who have not yet switched to UEFI, I have below > this simple little piece of code (partly found on the internet) that I > compile with nasm and I push onto the MBR. > > it runs perfectly on some PCs and in virtual machine with Qemu, but refuses > to run on other PCs by displaying either a kind of smiley logo or a simple > blinking cursor. > > does anyone have any idea or clue about this? > > regards, lacsaP. > > 8<-------------------------------- > ; nasm nobioscsm.asm -f bin -o nobioscsm > > bits 16 > org 0x7C00 > > start: > cli > mov si, msg > mov ah, 0x0E > .loop lodsb > or al, al > jz halt > int 0x10 > jmp .loop > > halt: > hlt > > msg: > db 0x0D, 0x0A, '** Boot with BIOS/CSM no longer supported : reboot with > EFI/UEFI **', 0 > > ;times 510 - ($-$$) db 0 > ;dw 0xAA55 >
