Btukfyl

I've written some simple bootloader that works good in QEMU and I decided to try it on real machine. I copied image file to flash drive and tried to load from it. But for some reason I've been getting just black screen with cursor somewhere near the top left corner and it made me think that it might be some problem with displaying strings on the screen. To check that idea I wrote simplistic bootloader that shows a message "Loading Image " and checks whether IO extensions (int 13h ah=42) are supported.If it's supported shows the message "Extensions are here". So in qemu it works and I'm getting these two messages as expected. But on my computer instead of two lines I'm getting one line like this "LoaExtensions are here". To print message I use int 10h ah=0Eh
I tried to set different video modes using ah=0 function of the int 10h but I've always got the same result.
Could you please help me to understand what could be wrong?
This is the code:

bits    16                      ; we are in 16 bit real mode

org     0                       ; we will set regisers later

start:  jmp Main                    ; jump to start of bootloader





msgLoading              db "Loading Image ", 0x0D, 0x0A, 0x00

msgSectorReadingError   db "ERROR: Can't read sectors from disk",0x0D,0x0A, 0x00

msgExtNotSupported      db "ERROR: BIOS doesn't support LBA",0x0D,0x0A, 0x00

msgErrWhileLoadingImage db "ERROR: Couldn't read seconday image",0x0D,0x0A, 0x00

msgExtSupported         db "Extensions are here",0x0D,0x0A, 0x00

imgName                 db "STAGE2  SYS"

;************************************************;





;************************************************;

;   Prints a string

;   DS=>SI: 0 terminated string

;************************************************;

Print:

            lodsb               ; load next byte from string from SI to AL

            or  al, al          ; Does AL=0?

            jz  PrintDone       ; Yep, null terminator found-bail out

            mov ah, 0xE         ; Nope-Print the character

            int 0x10

            jmp Print           ; Repeat until null terminator found

PrintDone:

            ret             ; we are done, so return



;************************************************;

;   Set Video mode

;

;************************************************;

SetVideoMode:

            mov ax,0x0002

            int 0x10

            ret





;***********************************************;

;   Checks whether BIOS supports extensions

;************************************************;

CheckExtenstions:



        xor ax,ax

        mov ah,0x41

        xor dx,dx

        mov dl,BYTE[driveNumber]

        mov bx,0x55AA

        int 0x13

        cmp bx,0xAA55

        jnz .error

        test cl,0x1

        jz .error

        jmp .exit

.error:

        mov si,msgExtNotSupported

        call Print

        cli

        hlt

.exit:

        mov si,msgExtSupported

        call Print

        cli 

        hlt

        ret









Main:



        ;----------------------------------------------------

        ; code located at 0000:7C00, adjust segment registers

        ;----------------------------------------------------



        cli                             ; disable interrupts

        mov     ax, 0x07C0              ; setup registers to point to our segment

        mov     ds, ax

        mov     es, ax

        mov     fs, ax

        mov     gs, ax



        ;----------------------------------------------------

        ; create stack

        ;----------------------------------------------------



        mov     ax, 0x0000              ; set the stack

        mov     ss, ax

        mov     sp, 0xFFFE

        mov     BYTE[driveNumber],dl

        sti                             ; restore interrupts

        call SetVideoMode

        mov     si, msgLoading          ; Show Loading Message

        call    Print



        call CheckExtenstions



        cli

        hlt



TIMES 510-($-$$) DB 0

DW 0xAA55