screen

[K.J.]

I don't think that the full source would help much but I was looking at your code and saw:

  ;videoseg base 0xB8000 limit 4000
  descriptor 48, 0FA0h, 08000h, 0Bh, 092h, 040h, 0

If your kernel is in real mode the videoseg base should be 0xB800 I think(anyone know for sure?). I suggest that maybe you should just use one of John Fine's bootsectors:

http://www.execpc.com/~geezer/johnfine/index.htm

K.J.

[mansonbound]

hey you dont need a gdt for realmode.

[mansonbound]

ok guys...heres what i found out:

i tried this:

Code: Select all

char *message="H A L L O ";

int main()
{
        movedata(DATA_SEL, message, SCREEN_DATA_SEL, 0, 3000);
        while(1);
}

and saw:

HALLO in the 4th line of the screen. The start of the 4zh Line has the offset 0x1E0. Had alook with a hexeditor:
0x1E0: H A L L O . So instead of the adress of message the function is called with 0 instead of message.

Any comments?

[K.J.]

Yeah, I don't get it.

K.J.

[mansonbound]

ok...its going on:

i threw away all the c code and did something in asm.
so i reserved mem for a variable:

a: DW 0x721
;(gray '!')
and i move it to the 1st characer of the vidmem.
mov eax, 0xB8000-0x80000
mov dx, [a]
mov [eax], dx

It works, when the variable is declared at an offset below 0x200. (moved the position of a with TIMES .... nop and looked at it in a hexeditor)

[Tim]

Is this code in a boot sector, or is it a file loaded by your boot sector code. Either way, it looks like you're only loading one sector.

[mansonbound]

It is a file loaded by the bootsector code.
And no! not just 512b are loaded, cause the Code (Also higher than 0x200 WORKS)

[mansonbound]

"ok...guess we can close the file on that one"

Hmm....i thought....everything above 0x200 is nil, but code over 0x200 works....so i had another look in the bootsectorcode, where the file is loaded and 512 is added to the adress after loading a sector:

mov bx, es
add bx, word [bps]       ;<<-----------heres the error
mov es, bx

so i fixed it and now it works.
TY for all the trouble that i've done to you