I'd suggest you find out how many bytes there are per pixel. I guess
you have 4 (not 1 you are using) and the resolution you think you see
is actually 640x120. You may also have limited video memory that makes
different resolutions use different pixel sizes
In Reply to:
2011/4/1 何闯 <justhechu...@163.com>:
> Deal all,
> I just tested int 0x10 BIOS interrupt to draw some pictures.
> However, when I coded the follow to enter 640X480 video mode, it seems
that
> the actual video mode is 640X100,
> I draw a rectangle with range(0,0, 640, 480) to verify, and it resulted in
> range(0,0, 640,100), about a quarter square of a rectangle.
> And I noticed that 320X200 video mode is OK, and 320X200 == 640X100, is
that
> mean my machine can hand only 64000 pixels?
> Can anyone tell me why?
>
////////////////////////////////////////////////////////////////////////////
///////////////////////////
> void setvga()
> {
> __asm__ __volatile__ ( REAL_CODE ( "movw $0x4f02, %%ax\n\t" //ax=0x0012
> here seem stay in the text mode
> "movw $0x0101, %%bx\n\t"
> "int $0x10\n\t" )::);
> }
> void putpixel(int x,int y,int c)
> {
> if(vediobuf == NULL)
> {
> vediobuf = (unsigned char*)phys_to_user(0xa0000); //physic address of
> graphic mode
> }
> *(vediobuf+x+640*y)=c;
> }
>
////////////////////////////////////////////////////////////////////////////
/////////////////////////
>
>
> yours,
> soforth
I'd suggest looking at other boot loaders and how they write to the
screen (including Syslinux's vesamenu.c32 and gfxboot.c32). 64,000
sounds like the 16-bit limit of 65,536 per segment.
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