Thanks for the clue, I will check the code in vesamenu.c32 and find why. ：）
At 2011-04-02，"Gene Cumm" <gene.c...@gmail.com> wrote: >On Fri, Apr 1, 2011 at 15:15, Vaza gpxe <vaza.g...@gmail.com> wrote: >> 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 > >I believe there should be only 4 bits at that video mode. > >Soforth, I'd suggest examining http://www.ctyme.com/intr/int-10.htm >for starters. I believe INT 10h AX 4F00h is the start of VESA related >info that Syslinux uses for vesamenu.c32 (and possibly gfxboot.c32) > >-- >-Gene > >> 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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