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The G400 is a video card made by Matrox, released in September 1999. The graphics processor contains a 2D GUI, video, and Direct3D 6.0 3D accelerator. Codenamed "Toucan", it was a more powerful and refined version of its predecessor, the G200. ==Overview== The Matrox G200 graphics processor had been a successful product, competing with the various 2D & 3D combination cards available in 1998. Matrox took the technology developed from the G200 project, refined it, and basically doubled it up to form the G400 processor. The new chip featured several new and innovative additions, such as multiple monitor output support, an all-around 32-bit rendering pipeline with high performance, further improved 2D and video acceleration, and a new 3D feature known as Environment Mapped Bump Mapping. Internally the G400 is a 256-bit processor, using what Matrox calls a "DualBus" architecture. This is an evolution of G200's "DualBus", which had been 128-bit. A Matrox "DualBus" chip consists of twin unidirectional buses internally, each moving data into or out of the chip. This increases the efficiency and bandwidth of data flow within the chip to each of its functional units. G400's 3D engine consists of 2 parallel pixel pipelines with 1 texture unit each, providing single-pass dual-texturing capability. The Millennium G400 MAX is capable of 333 megapixels per second fillrate at its 166 MHz core clock speed. It is purely a Direct3D 6.0 accelerator and, as such, lacks support for the later hardware transform and lighting acceleration of Direct3D 7.0 cards. The chip's external memory interface is 128-bit and is designed to use either SDRAM or SGRAM. Matrox released both 16 MiB and 32 MiB versions of the G400 boards, and used both types of RAM. The slowest models are equipped with 166 MHz SDRAM, while the fastest (G400 MAX) uses 200 MHz SGRAM. G400MAX had the highest memory bandwidth of any card before the release of the DDR-equipped version of NVIDIA GeForce 256. Perhaps the most notable feature of G400 is its ability to drive two separate monitors to display a single desktop. This feature is known as "DualHead" and was a decisive edge for Matrox over the card's competitors at the time. The DualHead capability not only offered desktop widening but also desktop cloning (two screens showing the same thing) and a special "DVDMAX" mode which outputs video overlays onto the second monitor. Matrox's award-winning Powerdesk display drivers and control panel integrated Dualhead in a very flexible and functional way that become world-renowned for its effectiveness. However, contrary to the video mode's name, G400 does not support full DVD decoding hardware acceleration. G400 does have partial support for the DVD video decoding process but it does not perform inverse discrete cosine transform IDCT or motion compensation in hardware (the two most demanding steps of the process). The G400 chip supports, in hardware, a texture-based surface detailing method called Environment Mapped Bump Mapping (EMBM). EMBM was actually created by BitBoys Oy and licensed to Matrox. EMBM was not supported by several competitors such as NVIDIA's GeForce 256 through GeForce 2, which only supported the simpler Dot-3 BM, but was available on the ATI Radeon 7200. Due to this lack of industry-wide support, and its toll on the limited graphics hardware of the time, EMBM only saw limited use during G400's time. Only a few games supported the feature, such as Dungeon Keeper 2 and Millennium Soldier: Expendable. EMBM requires either specialized hardware within the chip for its calculations or a more flexible and programmable graphics pipeline, such as later DirectX 8.0 accelerators like the GeForce 3 and Radeon 8500. G400's rendering pipelined uses what Matrox called Vibrant Color Quality 2 (VCQ2), a functionality in which all internal 3D calculations are done with 32-bit precision. The goal was to prevent dithering and other artifacts caused by inadequate precision when performing calculations. The result was the best quality 16-bit and 32-bit color modes available at the time. Matrox was known for their quality analog display output on prior cards and the G400 is no exception. G400 was the benchmark for signal quality for several years, significantly outperforming some competitors (notably pre-GeForce4 NVIDIA cards). Where many cards were crippled by blurry output, especially as the resolution and refresh rate increased, the Matrox cards delivered very sharp and clear images. G400 is the first Matrox board compatible with AGP 4X. Most (REV. A) G400 boards actually only support 2X mode, but there are later revisions (REV. B), that are fully 4X compliant and run at the higher speed if the motherboard is capable as well. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Matrox G400」の詳細全文を読む スポンサード リンク
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