;**************************************************************************** ;* ;* MegaGraph Graphics Library ;* ;* Copyright (C) 1993 Kendall Bennett. ;* All rights reserved. ;* ;* Filename: $RCSfile: sv_maxpg.asm $ ;* Version: $Revision: 1.2 $ ;* ;* Language: 80386 Assembler ;* Environment: IBM PC (MS DOS) ;* ;* Description: Module to compute the maximum number of available video ;* pages for specific video mode. ;* ;* $Id: sv_maxpg.asm 1.2 1993/03/07 04:04:13 kjb Exp $ ;* ;* Revision History: ;* ----------------- ;* ;* $Log: sv_maxpg.asm $ ;* Revision 1.2 1993/03/07 04:04:13 kjb ;* Bug fixes. ;* ;* Revision 1.1 1993/03/03 10:46:57 kjb ;* Initial revision ;* ;**************************************************************************** ; Table of standard video mode information (bytesPerLine, ; vertical resolution and number of colors) used to compute the number of ; pages and page size for the specified video mode. This table can be ; modified at initialisation time for video cards that have non-standard ; bytes per line values (S3 cards and VESA cards). PageInfo: dw grEGA_320x200x16, 40, 200 dw grEGA_640x200x16, 80, 200 dw grEGA_640x350x16, 80, 350 dw grVGA_640x400x16, 80, 400 dw grVGA_640x480x16, 80, 480 dw grSVGA_800x600x16, 100, 600 dw grSVGA_1024x768x16, 128, 768 dw grSVGA_1280x1024x16, 160, 1024 dw grVGA_320x200x256, 320, 200 dw grSVGA_640x350x256, 640, 350 dw grSVGA_640x400x256, 640, 400 dw grSVGA_640x480x256, 640, 480 dw grSVGA_800x600x256, 800, 600 dw grSVGA_1024x768x256, 1024, 768 dw grSVGA_1280x1024x256, 1280, 1024 dw grSVGA_320x200x32k, 640, 200 dw grSVGA_640x350x32k, 1280, 350 dw grSVGA_640x400x32k, 1280, 400 dw grSVGA_640x480x32k, 1280, 480 dw grSVGA_800x600x32k, 1600, 600 dw grSVGA_1024x768x32k, 2048, 768 dw grSVGA_1280x1024x32k, 2560, 1024 dw grSVGA_320x200x16m, 960, 200 dw grSVGA_640x350x16m, 1920, 350 dw grSVGA_640x400x16m, 1920, 400 dw grSVGA_640x480x16m, 1920, 480 dw grSVGA_800x600x16m, 2400, 600 dw grSVGA_1024x768x16m, 3072, 768 dw grSVGA_1280x1024x16m, 3840, 1024 dw -1 ;---------------------------------------------------------------------------- ; numPages ;---------------------------------------------------------------------------- ; ; Computes the number of pages in a specified video mode ; ; Entry: AX - Video mode number ; EBX - Video memory size ; ; Exit: AX - Number of video pages ; EBX - Page size for video mode ; CX - BytesPerLine value ; ; Registers: EAX,EBX,ECX,EDX ; ;---------------------------------------------------------------------------- PROC numPages mov edx,ebx ; EDX := video memory size mov bx,offset PageInfo - 6 @@FindMode: add bx,6 mov cx,[WORD cs:bx] cmp cx,-1 je @@NotFound cmp cx,ax jne @@FindMode ; Loop till desired mode is found push edx xor eax,eax mov ax,[WORD cs:bx+2] mul [WORD cs:bx+4] ; DX:AX := bytesPerLine * yres shl edx,16 or eax,edx ; EAX := bytesPerLine * yre pop edx cmp cx,grSVGA_640x350x256 jge @@Colors256 cmp cx,grVGA_320x200x256 je @@Colors256 ; We have a 16 color video mode. We round up the page size depending on ; how large it is, either to 8k, 16k, 32k or 64k boundaries. @@Colors16: shr edx,2 ; EDX := video memory / 4 add eax,1FFFh ; Round to next 8k and eax,0FFFFE000h cmp eax,2000h ; Page size = 8k? je @@Done ; Yes, we are done add eax,3FFFh ; Round to next 16k and eax,0FFFFC000h cmp eax,4000h ; Page size = 16k? je @@Done ; Yes, we are done add eax,7FFFh ; Round to next 32k and eax,0FFFF8000h cmp eax,8000h ; Page size = 32k? je @@Done ; Yes, we are done ; We have a 16 color video mode with > 64k per page, or a 256, 32k or ; 16 million color video mode. We thus ensure that the video page size is ; rounded up to the nearest 64k, to ensure pages always begin on bank ; boundaries. @@Colors256: add eax,0FFFFh ; Round to next 64k and eax,0FFFF0000h @@Done: mov cx,[WORD cs:bx+2] ; Load bytes per line value mov ebx,eax ; EBX := video page size mov eax,edx xor edx,edx ; EDX:EAX := video memory size div ebx ; EAX := number of video pages ret @@NotFound: xor ax,ax xor ebx,ebx ret ENDP numPages ;---------------------------------------------------------------------------- ; setBytesPerLine ;---------------------------------------------------------------------------- ; ; Changes the bytesPerLine value for a specified video mode. ; ; Entry: AX - Video mode number ; BX - New bytes per line value ; ; Exit: BX - New bytes per line value ; ; Registers: AX,BX ; ;---------------------------------------------------------------------------- PROC setBytesPerLine push cx push dx mov dx,bx ; BX := new bytesPerLine value mov bx,offset PageInfo - 6 @@FindMode: add bx,6 mov cx,[WORD cs:bx] cmp cx,-1 je @@NotFound cmp cx,ax jne @@FindMode ; Loop till desired mode is found ; Change the bytesPerLine value for the mode. ; ; Some VESA Video BIOS's are screwed and return invalid values for the ; bytes per line (Such as S3 based boards like the STB WIND/X). Generally ; they give us half the expected value, which is naturally less than the ; amount that is _physically_ required for the mode to operate. If this ; is the case we double the specified value :-) cmp dx,[WORD cs:bx+2] jge @@1 shl dx,1 ; Value is too small, so double it! @@1: mov [WORD cs:bx+2],dx mov bx,dx ; Restore value in BX @@NotFound: pop dx pop cx ret ENDP setBytesPerLine ;---------------------------------------------------------------------------- ; checkVESAPageFlip ;---------------------------------------------------------------------------- ; ; Checks to see if the VESA board supports extended page flipping. ; ; Exit: carry - Clear if VESA page flipping is supported ; ; Registers: AX,BX,CX,DX ; ;---------------------------------------------------------------------------- PROC checkVESAPageFlip mov ax,4F07h ; Set display start service xor bx,bx ; BH := 0, BL := 0 (set display start) xor cx,cx ; Left most pixel in line xor dx,dx ; First displayed scan line int 10h cmp al,4Fh jne @@Invalid ; Function not supported, no page flip or ah,ah jnz @@Invalid ; Function not successful, no page flip mov ax,4F07h ; Get display start service mov bx,1 ; BH := 0, BL := 1 (get display start) int 10h cmp al,4Fh jne @@Invalid ; Function not supported, no page flip or ah,ah jnz @@Invalid ; Function not successful, no page flip or bh,bh jnz @@Invalid ; BH should be zero if supported also or cx,cx jnz @@Invalid ; CX should be zero (from above call) or dx,dx jnz @@Invalid ; DX should be zero (from above call) ; Horrah! We have page flipping on a VESA board. clc ret @@Invalid: stc ret ENDP checkVESAPageFlip ;---------------------------------------------------------------------------- ; GetVESABytesPerLine - Gets the VESA bytes per line value for a mode ;---------------------------------------------------------------------------- ; ; Calls a VESA compatible BIOS to get the bytes per line value for a mode, ; and updates the internal tables accordingly. ; ; Entry: AX - MGL Mode number ; CX - VESA Mode Number ; ; Registers: None. ; ;---------------------------------------------------------------------------- PROC GetVESABytesPerLine pusha push ax push cs pop es mov di,offset VesaBuf ; ES:DI -> Buffer for VESA info mov ax,4F01h int 10h ; Call the video BIOS to get info pop bx cmp ax,004Fh jne @@Exit ; Call failed mov ax,bx mov bx,[WORD VesaBuf+16] call setBytesPerLine @@Exit: popa ret ENDP GetVESABytesPerLine ;---------------------------------------------------------------------------- ; ModifyS3BytesPerLine - Modifies the BytesPerLine for S3 cards. ;---------------------------------------------------------------------------- PROC ModifyS3BytesPerLine mov ax,grSVGA_800x600x16 mov cx,102h call GetVESABytesPerLine mov ax,grSVGA_1024x768x16 mov cx,104h call GetVESABytesPerLine mov ax,grSVGA_640x480x256 mov cx,101h call GetVESABytesPerLine mov ax,grSVGA_800x600x256 mov cx,103h call GetVESABytesPerLine mov ax,grSVGA_1024x768x256 mov cx,105h call GetVESABytesPerLine mov ax,grSVGA_640x480x32k mov bx,2048 call setBytesPerLine ret ENDP ModifyS3BytesPerLine