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VBE is made available through the Video Adapter's BIOS , which installs Interrupt vectors pointing at itself during system startup. Unfortunately, the older versions of VBE (those bundled with the vast majority of existing video boards) supported only a Real Mode interface, which couldn't be used without a significant performance penalty from within Protected Mode operating systems, such as Windows 95 or Linux . This meant that the VBE standard was almost never used for writing video-drivers, and each video board vendor had to invent a proprietary protocol for communicating with their own board(s). Despite this, many existing drivers still Thunk out to the real mode interrupt to initialize screen modes and gain direct access to a card's Linear Frame Buffer , tasks which would otherwise involve many hundred port writes that change from card to card. STANDARDS VESA BIOS Extensions (VBE Core) 2.0 1994 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 features include:
VESA BIOS Extensions (VBE Core) 3.0 1998 A superset of the VBE 2.0 standard. This standard adds Refresh Rate control, support for Stereo Glasses , improved multi-buffering support and other functions to the VBE 2.0 standard.
VBE/Accelerator Functions (VBE/AF) 1996 VBE/AF provides a low-level, standard interface to common acceleration functions available on most hardware. Some of the functions supported in the standard are access to hardware cursors, Bit Block Transfers (Bit Blt) , off screen Sprites , hardware panning, drawing and other functions. Supplemental specifications Supplemental specifications provides device independent interface between application software and Super VGA hardware. Function numbers are assigned by VESA Software Standards Committee (SSC). Power Management Extensions (PM) DPMS is a hardware standard that allows graphics cards to communicate with DPMS-compliant Monitor s via a special signaling system that can be used with existing graphics controllers and monitor cables. This signaling 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. Flat Panel Interface Extensions (FP) Allows access to special features in flat panel controllers. Audio Interface Extensions (AI) Provides standard to audio services. Currently (version 1.00), the VBE/AI specification defines three device classes: WAVE, MIDI, and VOLUME. Devices not supported: - CDROM control, which is covered by the Microsoft CDROM Extensions. - Effects Processors. This class of device will be expanded in future version of the VBE/AI specification. OEM Extensions Provides standard entry to vendor specific extensions. Display Data Channel (DDC) See Also: 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 . Serial Control Interface (SCI) Provides hardware independent means for operating system and application to read and write data over I&2C serial control interface. VESA VIDEO MODE NUMBERS Starting in VBE/Core 2.0, VESA no longer defines new VESA mode numbers and no longer require support of existing 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. 1: 32-bit is really (8:8:8:8), but the final 8-bit number is an "empty" alpha channel. It is otherwise equal to 24-bit color. EXTERNAL LINKS
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