Graphics address remapping table

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The graphics address remapping table (GART), [1] also known as the graphics aperture remapping table, [2] or graphics translation table (GTT), [3] is an I/O memory management unit (IOMMU) used by Accelerated Graphics Port (AGP) and PCI Express (PCIe) graphics cards. The GART allows the graphics card direct memory access (DMA) to the host system memory, through which buffers of textures, polygon meshes and other data are loaded. AMD later reused the same mechanism for I/O virtualization with other peripherals including disk controllers and network adapters. [4]

Accelerated Graphics Port expansion bus

The Accelerated Graphics Port (AGP) was designed as a high-speed point-to-point channel for attaching a video card to a computer system, primarily to assist in the acceleration of 3D computer graphics. It was originally designed as a successor to PCI-type connections for video cards. Since 2004, AGP has been progressively phased out in favor of PCI Express (PCIe); by mid-2008, PCI Express cards dominated the market and only a few AGP models were available, with GPU manufacturers and add-in board partners eventually dropping support for the interface in favor of PCI Express.

PCI Express computer expansion bus standard

PCI Express, officially abbreviated as PCIe or PCI-e, is a high-speed serial computer expansion bus standard, designed to replace the older PCI, PCI-X and AGP bus standards. It is the common motherboard interface for personal computers' graphics cards, hard drives, SSDs, Wi-Fi and Ethernet hardware connections. PCIe has numerous improvements over the older standards, including higher maximum system bus throughput, lower I/O pin count and smaller physical footprint, better performance scaling for bus devices, a more detailed error detection and reporting mechanism, and native hot-swap functionality. More recent revisions of the PCIe standard provide hardware support for I/O virtualization.

Direct memory access (DMA) is a feature of computer systems that allows certain hardware subsystems to access main system memory, independent of the central processing unit (CPU).

Contents

A GART is used as a means of data exchange between the main memory and video memory through which buffers (i.e. paging/swapping) of textures, polygon meshes and other data are loaded, but can also be used to expand the amount of video memory available for systems with only integrated or shared graphics (i.e. no discrete or inbuilt graphics processor), such as Intel HD Graphics processors. However, this type of memory (expansion) remapping has a caveat that affects the entire system: specifically, any GART, pre-allocated memory becomes pooled and cannot be utilised for any other purposes but graphics memory and display rendering.

Texture mapping method for defining high frequency detail, surface texture, or color information on a computer-generated graphic or 3D model

Texture mapping is a method for defining high frequency detail, surface texture, or color information on a computer-generated graphic or 3D model. Its application to 3D graphics was pioneered by Edwin Catmull in 1974.

Polygon mesh

A polygon mesh is a collection of vertices, edges and faces that defines the shape of a polyhedral object in 3D computer graphics and solid modeling. The faces usually consist of triangles, quadrilaterals, or other simple convex polygons, since this simplifies rendering, but may also be composed of more general concave polygons, or polygons with holes.

Operating system support

Linux

Jeff Hartmann served as the primary maintainer of the Linux kernel's agpgart driver, which began as part of Brian Paul's Utah GLX accelerated Mesa 3D driver project. The developers primarily targeted Linux 2.4.x kernels, but made patches available against older 2.2.x kernels. Dave Jones heavily reworked agpgart for the Linux 2.6.x kernels, along with more contributions from Jeff Hartmann. [5]

Linux kernel free and open-source Unix-like operating system kernel

The Linux kernel is a free and open-source, monolithic, Unix-like operating system kernel. The Linux family of operating systems is based on this kernel and deployed on both traditional computer systems such as personal computers and servers, usually in the form of Linux distributions, and on various embedded devices such as routers, wireless access points, PBXes, set-top boxes, FTA receivers, smart TVs, PVRs, and NAS appliances. While the adoption of the Linux kernel in desktop computer operating system is low, Linux-based operating systems dominate nearly every other segment of computing, from mobile devices to mainframes. As of November 2017, all of the world's 500 most powerful supercomputers run Linux. The Android operating system for tablet computers, smartphones, and smartwatches also uses the Linux kernel.

Brian Paul American software programmer

Brian E. Paul is a computer programmer who originally wrote and maintained the source code for the open source Mesa graphics library until 2012 and is still active in the project. Paul began programming initial source code in August 1993. Mesa is a free software/open source graphics library that provides a generic OpenGL implementation for rendering three-dimensional graphics on multiple platforms. Though Mesa is not an officially licensed OpenGL implementation, the structure, syntax and semantics of the API is that of OpenGL.

Utah GLX

Utah GLX was a project aimed at creating a fully free and open-source basic hardware-accelerated 3D renderer using the OpenGL rendering API on Linux kernel-based operating systems. Utah GLX predates Direct Rendering Infrastructure, which is what is used as of 2014.

FreeBSD

In FreeBSD, the agpgart driver appeared in its 4.1 release. [6]

FreeBSD free Unix-like operating system

FreeBSD is a free and open-source Unix-like operating system descended from the Berkeley Software Distribution (BSD), which was based on Research Unix. The first version of FreeBSD was released in 1993. In 2005, FreeBSD was the most popular open-source BSD operating system, accounting for more than three-quarters of all installed BSD systems.

Solaris

AGPgart support was introduced into Solaris Express Developer Edition as of its 7/05 release. [7]

See also

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References

  1. ↑ Accelerated Graphics Port Interface Specification: Revision 2.0 (PDF). 4 May 1998. p. 24.
  2. ↑ AGP V3.0 Interface Specification (PDF). September 2002. p. 116.
  3. ↑ freedesktop.org. "GART" . Retrieved 2010-03-05.
  4. ↑ AMD I/O Virtualization Technology (IOMMU) Specification, 32-bit to 64-bit Legacy I/O Device Mapping
  5. ↑ Jones, Dave (2003-07-24). "Ugly Ducklings: Resurrecting unmaintained code – agpgart adapted for Linux 2.6 kernel" (PDF). Archived from the original (PDF) on 2014-02-03. Retrieved 2014-06-05.
  6. ↑ "agp(4)". FreeBSD Man Pages: FreeBSD Kernel Interfaces Manual. freebsd.org. 2007-11-28. Retrieved 2014-06-10.
  7. ↑ "agpgart_io manpage". docs.sun.com. Sun Microsystems . Retrieved 2007-12-04.
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