=========================CUSTOM.DOC========================= Custom Super-VGA drivers: The driver SVGA.DRV is used in conjunction with the setup utility CUSTOM.EXE to customize a driver for resolutions up to 832x624. CUSTOM.EXE modifies your AUTOEXEC.BAT file to add a line of driver parameter information which SVGA.DRV uses to set your graphics board into the requested 16-color mode. In order to use CUSTOM.EXE, your board must support some Super-VGA mode at or below the above mentioned resolution (800x600 is most common). The video BIOS ROM on the board must support such a mode, 16-color drawing in that mode must be done using the standard VGA hardware registers, and the video memory must be mapped to the standard VGA address at segment 0A000H. All of the above qualifications must be confirmed in the hardware documentation which came with your board. If all of the above qualifications are met, then you may use CUSTOM.EXE to set up your system to run a 16-color 800x600 driver. You will also have to determine the mode number of the super-VGA graphics mode which you will wish to enter, and the setting of the CPU registers for the mode setting call (video INT 10h). This information should be in your hardware documentation. At the DOS prompt, invoke CUSTOM.EXE by typing: C> custom followed by a carriage return. CUSTOM will initially ask for the X- & Y-resolutions of the desired driver. Assuming we wish to generate an 800x600 driver, respond with the following: SVGA X-resolution [640]? 800 SVGA Y-resolution [480]? 600 Follow each response with a carriage return. The currently selected default appears in square brackets. If at any time you wish to select the default, respond with a carriage return. After specifying the screen resolution, CUSTOM now asks about aspect ratio correction. Most color monitors have the required 4:3 aspect ratio, so the correction factor 1.00 should be used. However it is expressed as a percentage; so, 1.00 = 100%. If your screen needs to be stretched in the vertical direction, use a percentage greater than 100; for example, the correction factor for EGA resolution (640x350) is 1.37, or 137%. For 800x600, the correction factor is 1.00, or 100%. Aspect ratio correction [100]? Page 1 =========================CUSTOM.DOC========================= The above line assumes that the computed default value, 100, is the one which is desired. CUSTOM will now ask for the CPU register values for the mode setting call (video INT 10H). A 16 bit CPU register value has two halves. The upper or high 8 bits of the AX register are in AH and the lower 8 bits are in AL. When CUSTOM asks for the values of the CPU registers required for setting your video card, you should supply both halves of the register as a single hexadecimal value. For example, if your hardware documentation specifies that AH should be set to 6Fh and AL set to 05h for a particular mode setting, then the AX register would have a value of 6F05. A typical user's manual for a video card may only give a mode value for a particular graphics resolution. In general, this assumes that AL should be set to that mode value and that AH should be set to 00h. For example, the Orchid Pro-Designer board requires a mode value of 29h. So the correct responses for the Orchid board are: Hexadecimal MODE value for AX [0012]? 0029 Hexadecimal MODE value for BX [0000]? Hexadecimal MODE value for CX [0000]? Hexadecimal MODE value for DX [0000]? Note that BX, CX, and DX are "don't care's" and are indicated by responding with a carriage return. For the Video 7 VRAM board, the mode setting call requires AX=6F05h, and BX=62h; CX and DX are don't care values. Note that BX=62h is the same as BX=0062h which is the same as BH=00h and BL=62h. The correct responses are as follows for the Video 7 VRAM board: Hexadecimal MODE value for AX [0012]? 6F05 Hexadecimal MODE value for BX [0000]? 0062 Hexadecimal MODE value for CX [0000]? Hexadecimal MODE value for DX [0000]? After the above dialog, you will be allowed to go back and make any corrections: Do you wish to change any of the above [Y]? N Respond "N" when you are satisfied. Finally you will be asked if you wish to change your AUTOEXEC.BAT file. If you choose to modify this file, then every time you boot, the correct environment setting for TANGODRV= will be placed in the environment. Otherwise, the file SVGA.BAT will be created in directory C:\, and will have to be executed whenever you wish to set the TANGODRV= environment variable. Do you wish to update AUTOEXEC.BAT now [N]? Page 2 =========================CUSTOM.DOC========================= If you choose "N", then the following comment will appear: Updating the file C:\SVGA.BAT If you choose "Y", then the following comment will appear: Updating the file C:\AUTOEXEC.BAT You must either execute the batch file "SVGA", or re-boot your computer to make sure the TANGODRV= environment variable is properly set. You may confirm its setting with the DOS command "SET", used to examine the environment variable settings. With TANGODRV= set properly, you may now run the TANGO application program, say, PCB or SCH, specifying SVGA as the driver: PCB /g:SVGA or; e.g., SCH /g:C:\TANGO\MYDIR\SVGA The first example above assumes that SVGA.DRV exists in the directory from which you invoke PCB. Otherwise you will have to precede the driver name with a full pathname, as in the second example for SCH. Note that you need only invoke the application in this manner once; it will remember what graphics driver to use in the future. Lastly, if the CUSTOMized driver does not work, revert to the VGA driver with: PCB /g:VGA Page 3
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