VESA BIOS Extension

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VESA BIOS Extension (VBE) is a standard developed in the 1990s by the Video Electronics Standards Association (VESA) for graphics cards in IBM-compatible personal computers (PCs).

It is a programming interface (API) usually implemented in the graphics card BIOS , which makes interrupts available to the programs in order to carry out actions such as setting or querying video modes and to address other functions supported by the hardware. Today's counterparts such as DirectX and OpenGL are implemented on the operating system level.

The VESA BIOS Extension was primarily intended for 16-bit applications under DOS . The frame buffer can, however, also be used by 32-bit DPMI programs. With the introduction of VBE 2.0 it was possible to use graphics modes in 16-bit color depth (65,536 colors) with resolutions of up to 1600 × 1200 pixels without specifically implementing program-internal distinctions to the graphics hardware used. Under DOS there was previously no standardized interface for graphics that went beyond the VGA standard.

The current version of the 3.0 standard is backwards compatible with the previous 2.0 specification. It is supported by most modern nVidia graphics cards, but is rarely used by application software anymore, since today's programs no longer address the hardware directly (see below). At that time, the innovations introduced with the 3.0 standard were not used compared to the 2.0 standard, since all the essential functions are already available with the 2.0 standard. The main innovation was the Protected Mode Entry Point , which can be accessed from 16- and 32-bit Protected Mode. In addition, APIs that are independent of the graphics card are used in desktop systems such as Microsoft Windows and Linux , which then implement the corresponding functionality via manufacturer-specific drivers with defined interfaces. Furthermore, especially with laptops, some of the modes are overwritten with WXGA resolutions due to the special display sizes there .

Most MS-DOS- based games between 1993 and 1997 used the fast 16-bit, low-resolution modes such as 320 × 200 or 320 × 240, later 640 × 480. However, since not all graphics cards implemented the corresponding functionality in their BIOS when this standard was introduced, there were universal additional programs ( e.g. UniVBE , later Scitech Display Doctor ) as well as hardware- specific additional programs ( e.g. S3VBE Core 2.0 for S3 graphics cards or TLIVESA for Tseng-Labs graphics cards ) who offered appropriate support. Only then could the modes be used in appropriate cases.

The standard still plays a role today in operating systems for which there is no special driver support for a specific graphics chipset. If, for example, no graphics card drivers are available for certain graphics cards for Windows, Linux or FreeBSD, resolutions of more than 640 × 480 pixels with more than 256 colors can only be used by using a VESA driver that uses the functionality described here.

On Windows, VESA mode is used extensively in safe mode , because in this mode no manufacturer-specific 3rd party drivers are usually loaded.

However, the standard does not cover 2D or 3D accelerator functions . When displaying 2D or 3D content, the CPU has to render everything in software.

List of modes

Mode
( hexadecimal )
Resolution
( pixel × pixel)
Color depth
(bit)
0x100 0640 × 0400 08th
0x101 0640 × 0480 08th
0x102 0800 × 0600 04th
0x103 0800 × 0600 08th
0x104 1024 × 0768 04th
0x105 1024 × 0768 08th
0x106 1280 × 1024 04th
0x107 1280 × 1024 08th
0x108 0080 × 0060 (text) 04th
0x109 0132 × 0025 (text) 04th
0x10A 0132 × 0043 (text) 04th
0x10B 0132 × 0050 (text) 04th
0x10C 0132 × 0060 (text) 04th
0x10D 0320 × 0200 15th
0x10E 0320 × 0200 16
0x10F 0320 × 0200 24
0x110 0640 × 0480 15th
0x111 0640 × 0480 16
0x112 0640 × 0480 24
0x113 0800 × 0600 15th
0x114 0800 × 0600 16
0x115 0800 × 0600 24
0x116 1024 × 0768 15th
0x117 1024 × 0768 16
0x118 1024 × 0768 24
0x119 1280 × 1024 15th
0x11A 1280 × 1024 16
0x11B 1280 × 1024 24
0x11C 1600 × 1200 08th
0x11D 1600 × 1200 15th
0x11E 1600 × 1200 16
0x11F 1600 × 1200 24

With bits can be different colors represent. Since 8 bits are available for the red, green and blue components of a pixel, different colors are possible for a pixel, also called true color (see also RGB color space ). With a color depth of 16 bits, 65,536 different colors are possible for a pixel, which is called high color .

See also

Web links