Re: simple message under BIOS/CSM/LEGACY

[SteveSi]

Maybe clear direction flag first?

cld

??


On Mon, 1 Aug 2022 at 08:40, Pascal <patatetom@gmail.com> 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
>