VESA BIOS Extensions (VBE) is a VESA standard, currently at version 3, that defines the interface that can be used by software to access compliant video boards at high resolutions and bit depths. This is opposed to the "traditional" INT 10h BIOS calls, which are limited to resolutions of 640×480 pixels with 16 colour (4-bit) depth or less. VBE is made available through the video card's BIOS, which installs some interrupt vectors that point to itself during boot up.
Most newer cards implement the more capable VBE 3.0 standard. Older versions of VBE provide only a real mode interface, which cannot be used without a significant performance penalty from within protected mode operating systems. Consequently, the VBE standard has almost never been used for writing a video card's drivers; each vendor has thus had to invent a proprietary protocol for communicating with its own video card. Despite this, it is common that a driver thunk out to the real mode interrupt in order to initialize screen modes and gain direct access to a card's linear frame buffer, because these tasks would otherwise require handling many hundreds of proprietary variations that exist from card to card.
In EFI 1.x systems, the INT 10H and the VESA BIOS Extensions (VBE) are replaced by the EFI UGA protocol. In widely used UEFI 2.x systems, the INT 10H and the VBE are replaced by the UEFI GOP.[1] [2]
VBE 1.0 (VS891001) was defined in 1989.[3] VBE 1.1 (VS900602) was defined in 1990. VBE 1.2 (VS911022) was defined in 1991.[4] These versions of VBE require real mode to work.
VBE defines several new functions called through INT 10H. The function numbering start with AX=4F00, or (AH=4F, AL=00), for Function 00h. 00h to 05h were defined in VBE 1.0, 06h and 07h in 1.1, and 08h in 1.2.
This standard provides the primary functionality of the VESA BIOS Extensions. It allows applications to determine the capabilities of the graphics card and provides the ability to set the display modes that are found. VBE 2.0 adds some new features above the prior VBE 1.2 standard including linear framebuffer access and protected mode banking. Some of the VBE Core 2.0[5] features include:
A superset of the VBE 2.0 standard. This standard adds refresh rate control, facilities for stereo glasses, improved multi-buffering and other functions to the VBE 2.0 standard.
A new "Protected Mode Entry Point" was added as an alternative to Function 0Ah.
VBE/AF provides a low-level, standard interface to common acceleration functions available on most hardware. Some of the functions defined in the standard are access to hardware cursors, Bit Block Transfers (Bit Blt), off screen sprites, hardware panning, drawing and other functions. It is defined to work under 32-bit protected mode. Despite the widespread adoption of VBE Core, very few devices support VBE/AF. The FreeBE/AF project implements free third-party VBE/AF drivers for certain graphics cards.
Supplemental specifications provides device independent interface between application software and Super VGA hardware. Function numbers are assigned by VESA Software Standards Committee (SSC).
DPMS is a hardware standard that allows graphics cards to communicate with DPMS-compliant monitors via a special signalling system that can be used with existing graphics controllers and monitor cables. This signalling system allows the graphics card to tell the monitor to go into a number of different power management or power saving states, which effectively allow the monitor to turn itself off when it is not in use.
Allows access to special features in flat panel controllers.
Provides standard to audio services.
Currently (version 1.00), the VBE/AI specification defines three device classes: WAVE, MIDI, and VOLUME. Device types not covered:
Provides standard entry to vendor-specific extensions.
See main article: article and Display Data Channel. The Display Data Channel or DDC is a digital connection between a computer display and a graphics adapter that allows the display to communicate its specifications to the adapter. The standard was created by VESA.
Provides hardware independent means for operating system and application to read and write data over I²C serial control interface.
Although mode number is a 16-bit value, the optional VBE mode numbers are 14 bits wide. Bit 15 is used by VGA BIOS as a flag to clear or preserve display memory.VBE defined mode numbers as follows:
| Bit | Meaning | |
|---|---|---|
| 0–8 | Mode numbers. If bit 8 is 1, it is a VESA defined VBE mode. | |
| 9-10 | Reserved for expansion. Must be set to 0. | |
| 11 | Refresh rate control Select. If set to 1, use user specified CRTC values for refresh rate, otherwise use BIOS default refresh rate. | |
| 12–13 | Reserved for VBE/AF. Must be set to 0. | |
| 14 | Linear/Flat Frame Buffer Select. If set to 1, use linear frame buffer, otherwise use banked frame buffer. | |
| 15 | Preserve Display Memory Select. If set to 1, preserve display memory, otherwise clear display memory. |
Starting in VBE/Core 2.0, VESA no longer defines new VESA mode numbers and no longer requires a device to implement the old numbers. To properly detect information of a screen mode, use Function 01h - Return VBE Mode Information.
Mode 81FFh is a special video mode designed to preserve current memory contents and give access to the entire video memory.
Beginning with the VBE 2.0 standard, no new modes will be defined by VESA, and old modes are no longer mandatory. The use of defined modes should be considered deprecated: modern video cards may or may not use these mode numbers (even though most do for backward compatibility), and modern software should not use them. The correct way for software to discover available display modes is to obtain a list of modes (using "Function 00h - Return VBE Controller Information") and then to check each mode (using "Function 01h: Return VBE Mode Information") until it finds the mode/s it requires.
| Graphics modes | 320×200 | 640×400 | 640×480 | 800×600 | 1024×768 | 1280×1024 | |
|---|---|---|---|---|---|---|---|
| 16-color palette | 258 (0102h), 106 (6Ah) | 260 (0104h) | 262 (0106h) | ||||
| 256-color palette | 256 (0100h) | 257 (0101h) | 259 (0103h) | 261 (0105h) | 263 (0107h) | ||
| 15-bit (5:5:5) | 269 (010Dh) | 272 (0110h) | 275 (0113h) | 278 (0116h) | 281 (0119h) | ||
| 16-bit (5:6:5) | 270 (010Eh) | 273 (0111h) | 276 (0114h) | 279 (0117h) | 282 (011Ah) | ||
| 24-bit (8:8:8) | 271 (010Fh) | 274 (0112h) | 277 (0115h) | 280 (0118h) | 283 (011Bh) |
Modes 264–268 are text modes. 264 (0108h) is 80 columns × 60 rows (80×60), 265 (0109h) is 132×25, 266 (010Ah) is 132×43, 267 (010Bh) is 132×50 and 268 (010Ch) is 132×60.
| Text modes | Columns | ||
|---|---|---|---|
| Rows | 80 | 132 | |
| 25 | 265 (0109h) | ||
| 43 | 266 (010Ah) | ||
| 50 | 267 (010Bh) | ||
| 60 | 264 (0108h) | 268 (010Ch) | |
The table below combines the modes defined by VESA (the values denoted in black) along with modes commonly used, but which may not work on all graphics cards as they are not defined by any standard .
| Graphics modes | 320×200 | 640×400 | 640×480 | 800×600 | 1,024×768 | × | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 16-color palette | [6] | 258 (0102h), 106 (6Ah) | 260 (0104h) | 262 (0106h) | ||||||||||
| 256-color palette | 256 (0100h) | 257 (0101h) | 259 (0103h) | 261 (0105h) | 263 (0107h) | [7] | ||||||||
| 15-bit (5:5:5) | 269 (010Dh) | 272 (0110h) | 275 (0113h) | 278 (0116h) | 281 (0119h) | |||||||||
| 16-bit (5:6:5) | 270 (010Eh) | 273 (0111h) | 276 (0114h) | 279 (0117h) | 282 (011Ah) | |||||||||
| 24-bit (8:8:8) | 271 (010Fh) | 274 (0112h) | 277 (0115h) | 280 (0118h) | 283 (011Bh) | |||||||||
| [8] | [9] |
A few tools have been written to detect VBE modes available on a system. They generally work by invoking Function 01h, which is more reliable than assuming a table of extented modes as it's part of the device's self-documentation.
hwinfo --framebuffer reports graphics information, including VESA modes on a "Mode" line.The Linux kernel allows the user to select the VESA mode at boot time by passing a code in memory to the kernel. The LILO boot loader passes this code based on a "vga" parameter in its configuration file. It takes the form 'vga=XXX', where XXX is the decimal value, or 'vga=0xHHH', where HHH is the hexadecimal value. However, the 'vga=' boot loader parameter does not directly accept VESA video mode numbers; rather, the Linux video mode number is the VESA number plus 512 (in the case of the decimal representation) or plus 0x200 (in the case of the hexadecimal representation). For example, the defined VESA value of 257 (0x101), representing 640x480 and 256 colours, has an equivalent Linux video mode value of 769 (0x301).[12]
As indicated earlier, the VESA standard defines a limited set of modes; in particular, none above × are covered and, instead, their implementation is completely optional for graphics adapter manufacturers. As vendors are free to utilize whatever additional values they please, this means that, in the table below, the modes (and expressed in decimal form) may not apply to every graphics adapter!
| ! 320×200 | 640×400 ! 640×480 | 800×500 ! 800×600 | 896×672 ! ×640 | ×768 ! ×720 | ×1,024 ! ×1,050 | ×900 ! ×1,200 | × ! × | - !16 colors | 770 0302h | 772 0304h | 774 0306h | - ! 256 colors | 768 0300h | 769 0301h | 879 036Fh | 771 0303h | 815 032Fh | 874 036Ah | 773 0305h | 775 0307h | - ! 15-bit (5:5:5) | 781 030Dh | 801 0321h | 784 0310h | 880 0370h | 787 0313h | 816 0330h | 875 036Bh | 790 0316h | 793 0319h | - ! 16-bit (5:6:5) | 782 030Eh | 802 0322h | 785 0311h | 881 0371h | 788 0314h | 817 0331h | 876 036Ch | 791 0317h | 794 031Ah | - ! 24-bit (8:8:8) | 783 030Fh | 803 0323h | 786 0312h | 882 0372h | 789 0315h | 818 0332h | 877 036Dh | 792 0318h | 795 031Bh | - ! 32-bit (8:8:8)1 |
|---|
VGA= also appears to select ×800 (8-bit) for various laptops' displays.
VGA= is ×
The VESA BIOS emulation in the Parallels virtual machine has a different set of non-standard VESA modes. As of build 3214, LRMI vbetest reveals these modes:
| ! 640×400 | 640×480 ! 720×480 | 800×500 ! 800×600 | 896×672 ! ×640 | ×768 ! ×720 | ×1,024 ! ×900 | ×1,200 | - ! 256 color palette | 256 (0100h) | 257 (0101h) | 367 (016Fh) | 364 (016Ch) | 259 (0103h) | 297 (0129h) | 358 (0166h) | 261 (0105h) | 355 (0163h) | 263 (0107h) | 352 (0160h) | 284 (011Ch) | - ! 15-bit (5:5:5) | 272 (0110h) | 275 (0113h) | 278 (0116h) | 281 (0119h) | 285 (011Dh) | - ! 16-bit (5:6:5) | 289 (0121h) | 273 (0111h) | 368 (0170h) | 365 (016Dh) | 276 (0114h) | 298 (012Ah) | 359 (0167h) | 279 (0117h) | 356 (0164h) | 282 (011Ah) | 353 (0161h) | 286 (011Eh) | - ! 24-bit (8:8:8) | 290 (0122h) | 274 (0112h) | 369 (0171h) | 366 (016Eh) | 277 (0115h) | 299 (012Bh) | 360 (0168h) | 280 (0118h) | 357 (0165h) | 283 (011Bh) | 354 (0162h) | 287 (011Fh) |
|---|
The VESA BIOS emulation in the VirtualBox virtual machine has a different set of non-standard VESA modes. As of 6.1.38_Ubuntu build r153438, the VESA BIOS function AX=0x4F01 reveals these modes (See also VBETables-gen.c):
| !320x200 | 640×400 ! 640×480 | 800×600 ! ×768 | ×864 ! ×1024 | ×1200 | - | 4-bit palette | 260(0104h) | 262(0106h) | ||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 256 color palette | 326(0146h) | 256(0100h) | 257(0101h) | 259(0103h) | 261(0105h) | 328(0148h) | 263(0107h) | |||||||
| 15-bit (5:5:5) | 269(010dh) | 272(0110h) | 275(0113h) | 278(0116h) | 329(0149h) | 281(0119h) | ||||||||
| 16-bit (5:6:5) | 270(010eh) | 273(0111h) | 276(0114h) | 279(0117h) | 330(014ah) | 282(011Ah) | ||||||||
| 24-bit (8:8:8) | 271(010fh) | 274(0112h) | 277(0115h) | 280(0118h) | 331(014bh) | 283(011Bh) | ||||||||
| 32-bit (x:8:8:8) | 320(0140h) | 321(0141h) | 322(0142h) | 323(0143h) | 324(0144h) | 332(014ch) | 325(0145h) | 327(0147h) |