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1A GPU is the common term for a piece of a computer/console/arcade hardware that is dedicated to drawing things, i.e. graphics. The general purpose of a GPU is to relieve the [[UsefulNotes/CentralProcessingUnit CPU]] of the responsibility for a significant portion of rendering. This also gives performance benefits as it gives the CPU time for core program code, which in turn may be able to tell the GPU what to do more often. Both consoles and regular computers have had various kinds of [=GPUs=]. They had two divergent kinds of 2D [=GPUs=], but they converged with the advent of 3D rendering.˛˛The term "GPU" was coined by [=nVidia=] upon the launch of their [=GeForce=] line of hardware. This was generally a marketing stunt (as they [[BlatantLies claimed]] to have "invented the GPU" despite prior work by others), though the [=GeForce=] did have some fairly advanced processing features in it. However, the term GPU has become the accepted shorthand for ''any'' graphics processing chip, even [=pre-GeForce=] ones.˛˛˛!!CPU Driven Graphics˛˛One fascinating fact: Some very early home computers and consoles lacked what we would call a "GPU", instead only having a chip for interfacing with the Monitor with the CPU, and thus lacked any kind of chip that we would call a Graphics Processing Unit--that is, while they had a graphics ''chip'', that chip was effectively run entirely by the CPU, with no ability to function on their own. This was only possible because of design quirks in analogue television and monitor standards. In short, the image displayed on analogue televisions is surrounded by a field of "blacker then black" used to align the image properly. Non-display Processing could only take place during the period that this overscan field was being "drawn". (Note that many systems as late as the 1990s used these quirks as well for other reasons--most notably, the horizontal blanking period was a good time to do things to achieve a parallax effect; for further information, go look up "hblank" and "vblank")˛˛Needless to say, this was horribly inefficient, but when the RAM needed for anything resembling a GPU was prohibitively expensive, it was also required to keep the costs of hardware down.˛˛The most notable systems to have CPU-driven graphics were the Atari 2600 and Sinclair ZX81; a notable (and slightly insane) variation was the [[ Vectrex]]. (A few "post-modern" systems also use this method; for example, the [[ Gigatron TTL]], as a GPU would violate the "computer without a microprocessor" gimmick of the system.)˛˛!!Arcade 2D GPU˛˛The first [[ 2D GPU chipsets]] appeared in early UsefulNotes/{{Arcade Game}}s of the 1970's. The earliest known example was the Fujitsu [=MB14241=], a video shifter chip that was used to handle graphical tasks in Creator/{{Taito}} & Creator/{{Midway}} titles such as ''VideoGame/GunFight'' (1975) and ''VideoGame/SpaceInvaders'' (1978). Taito and Creator/{{Sega}} began manufacturing dedicated video graphics boards for their arcade games from 1977. In 1979, [[Creator/BandaiNamcoEntertainment Namco]] and Creator/{{Irem}} introduced tile-based graphics with their custom arcade graphics chipsets. The [[ Namco Galaxian]] arcade system in 1979 used specialized graphics hardware supporting RGB color, multi-colored sprites and tilemap backgrounds. Creator/{{Nintendo}}'s ''[[ Radar Scope]]'' video graphics board was able to display hundreds of colors on screen for the first time.˛˛By the mid-80's, Sega were producing [[ Super Scaler]] GPU chipsets with advanced [[ three-dimensional]] [[ sprite/texture scaling]] graphics that would not be rivalled by home computers or consoles until the 1990s.˛˛From the 1970s to the 1990s, arcade GPU chipsets were significantly more powerful than GPU chipsets for home computers and consoles, both in terms of 2D and [[ 3D graphics]]. It was not until the mid-90's that home systems rivalled arcades in 2D graphics, and not until the early 2000s that home systems rivalled arcades in 3D graphics.˛˛!!Console 2D GPU˛˛This kind of GPU, introduced to home systems by the [[ Texas Instruments TMS9918/9928]] and popularized by the UsefulNotes/{{NES}}, UsefulNotes/SegaMasterSystem and UsefulNotes/SegaGenesis, forces a particular kind of look onto the games that use them. You know this look: everything is composed of a series of images, tiles, that are used in various configurations to build the world.˛˛This enforcement was a necessity of the times. Processing power was limited, and while tile-based graphics were somewhat limited in scope, it was ''far'' superior to what could be done without this kind of GPU.˛˛In this GPU, the tilemaps and the [[ sprites]] are all built up into the final image by the GPU hardware itself. This drastically reduces the amount of processing power needed -- all the CPU needs to do is upload new parts of the tilemaps as the user scrolls around, adjust the scroll position of the tilemaps, and say where the sprites go.˛˛Tilemap rendering is essentially a form of bitmap framebuffer compression. An entire screen could be filled with the same tiles re-drawn many times, without affecting performance, which was ideal for 2D games. This drastically reduced processing, memory, fillrate and bandwidth requirements by up to 64 times.˛˛The UsefulNotes/NintendoEntertainmentSystem, for example, renders a 256x240 background and sixty-four 8x16 sprites at 60 frames/second, a tile fillrate equivalent to more than 4 megapixels/second, higher than what PC games rendered to a bitmap framebuffer until the early 1990s. The UsefulNotes/SegaGenesis renders two 512x512 backgrounds and eighty 32x32 sprites at 60 frames/second, a tile fillrate equivalent to more than 30 megapixels/second, higher than what PC games rendered in a bitmap framebuffer until the mid-1990s.˛˛!!Computer 2D GPU˛˛Computers had different needs. Computer 2D rendering was driven by the needs of applications more so than games. Therefore, rendering needed to be fairly generic. Such hardware had a framebuffer, an image that represents what the user sees. And the hardware had [[UsefulNotes/VideoRAM video memory]] to store extra images that the user could use.˛˛Such hardware had fast routines for drawing colored rectangles and lines. But the most useful operation was the blit or [=BitBlt=]: a fast video memory copy. Combined with video memory, the user could store an image in VRAM and copy it to the frame buffer as needed. Some advanced 2D hardware had scaled-blits (so the destination location could be larger or smaller than the source image) and other special blit features.˛˛Some 2D [=GPUs=] combined these two approaches, having both a framebuffer and a tilemap, and being able to output hardware accelerated sprites and tiles, and perform tile transformation routines over what was stored in the framebuffer. These were most powerful and advanced among them, but usually pretty specialized and tied to the specific platforms (such as the Amiga, X68000 and FM Towns), and in the end more general approach won over, being more conducive to the various performance-enchancing tricks and better adapting to the increasing computing horsepower and transition to 3D gaming.˛˛The CPU effort is more involved in this case. Every element must be explicitly drawn by a CPU command. The background was generally the most complicated. This is why many early computer games used a static background. They basically had a single background image in video memory which they blitted to the framebuffer each frame, followed by a few sprites on top of it.˛˛The [[ NEC µPD7220]], released in 1982, was one of the first implementations of a computer GPU as a single Large Scale Integration (LSI) integrated circuit chip, enabling the design of low-cost, high-performance video graphics cards such as those from Number Nine Visual Technology. It became one of the best known of what were known as graphics processing units in the 1980s.˛˛PC [=GPUs=] of that era were designed for static desktop acceleration, rather than video game acceleration, so PC [=CPUs=] had to render games in software. As such, PC games were unable to match the smooth scrolling of consoles, due to consoles using tile-based [=GPUs=], which reduced processing, memory, fillrate and bandwidth requirements by up to 64 times. It was not until 1991, with the release of ''[[VideoGame/CommanderKeen Keen Dreams]]'', that PC gaming caught up to the smooth 60 frames/second scrolling of the aging UsefulNotes/NintendoEntertainmentSystem.˛˛The 80486DX2/66, a high-end gaming CPU of the early 90s, ran at 66 [=MHz=] and could run 32-bit code as an "extension" to 16-bit DOS. While faster than the CPU of the UsefulNotes/SegaGenesis and UsefulNotes/SuperNES, that alone was not enough to surpass them, as both consoles had tile-based [=GPUs=], which [=PCs=] were lacking at the time. It was through various programming tricks that [=PCs=] were able to exceed the Genesis and Super NES, by taking advantage of quirks in the way early [=PCs=] and VGA worked. Creator/JohnCarmack once described the engine underpinning his company's breakout hit ''VideoGame/Wolfenstein3D'' as "a collection of hacks", and he was not too far off. It was also the last of their games that could run in a playable state on an 80286 PC with 1 MB RAM -- a machine that was considered low-end even in 1992 -- which serves as a testament to the efficiency of some of those hacks.˛˛Before the rise of Windows in the mid-1990s, most PC games couldn't take advantage of newer graphics cards with hardware blitting support (or even the framebuffer, for that matter- as a matter of fact, many earlier GPUs drew directly to the screen memory and lacked a framebuffer). While the first ''accelerated'' graphics card came out in 1991, many games that were written ignored the features- the CPU had to do all the work, and this made both a fast CPU and a fast path to the video RAM essential. [=PCs=] with local-bus video and 80486 processors were a must for games like ''VideoGame/{{Doom}}'' and ''VideoGame/{{Heretic}}''; playing them on an old 386 with ISA video was possible, but wouldn't be very fun. The only program that could remotely take advantage of the features found in these new cards was Windows 3.0, and even then games for the platform were mostly graphically simple as it was deemed to be too taxing to handle graphics-heavy games.˛˛However, starting in the mid-90s with the creation of the [=DirectX=] (and specifically [=DirectDraw=]) API, as well as the introduction of hardware-accelerated [=QuickTime=] cards on the Macintosh front, games were finally able to take advantage of blitting, and the future of [=PCs=] moved from one that is mostly business oriented to one that is more oriented to gaming and multimedia. ˛˛!!Basic 3D GPU˛˛The basic [[ 3D-based]] GPU is much more complicated. It isn't as limiting as the NES-style 2D GPU.˛˛This GPU concerns itself with drawing triangles. Specifically, triangles that appear to imitate shapes. They have special hardware in them that allows the user to map images across the surface of a triangular mesh, so as to give it surface detail. When an image is applied in this fashion, it is called a ''texture''.˛˛The early forms of this GPU were just triangle/texture renderers. The CPU had to position each triangle properly each frame. Later forms, starting with arcade systems like the [[ Sega Model 2]] and [[ Namco System 22]], then the UsefulNotes/Nintendo64 console, and then the first [=GeForce=] PC chip, incorporated triangle [[,_clipping,_and_lighting transform and lighting]] into the hardware. This allowed the CPU to say, "here's a bunch of triangles; render them," and then go do something else while they were rendered.˛˛!!Modern 3D GPU˛˛In the early 2000s, something happened in GPU design.˛˛Take the application of textures to a polygon. The very first GPU had a very simple function. For each pixel of a triangle:˛˛->color = textureColor * lightColor˛˛A simple equation. But then, the UsefulNotes/{{Dreamcast}} released with hardware bump mapping capabilities, so developers wanted to apply 2 textures to a triangle. So this function became more complex:˛˛->color = texture1 * lightColor * texture2˛˛Interesting though this may be, developers wanted more say in how the textures were combined. That is, developers wanted to insert more general math into the process. So GPU makers added a few more switches and complications to the process.˛˛The [=GeForce=] 3, followed soon after by the UsefulNotes/GameCube and UsefulNotes/{{Xbox}} consoles, basically decided to say "Screw that!" and let the developers do arbitrary stuff:˛˛->color = Write it Yourself!˛˛What used to be a simple function had now become a user-written ''program''. The program took texture colors and could do fairly arbitrary computations with them.˛˛In the early days, "fairly arbitrary computations" was quite limited. Nowadays, not so much. These GPU programs, called ''shaders'', commonly do things like video decompression and other sundry activities. At first the shader execution units that did shaders were separated into pipelines for strictly vertex (positioning the 3D models) and pixels (for coloring) though with some clever programming, general operations could be done. Shader units in modern [=GPUs=] became generalized to take on any work. This led to to the General Purpose GPU, or GPGPU, which could do calculations much faster than a several traditional [=CPUs=] in tandem.˛˛!!Difference between GPU and CPU˛[=GPUs=] and [=CPUs=] are built around some of the same general components, but they're put together in very different ways. A chip only has a limited amount of space to put circuits on, and [=GPUs=] and [=CPUs=] use the available space in different ways. The differences can be briefly summarized as follows:˛˛* Execution units: These are the things that do things like add, multiply, and other actual work. A GPU has dozens of times as many of these as a CPU, so it can do a great deal more total work than a CPU in a given amount of time, if there's enough work to do.˛* Control units: These are the things that read instructions and tell the execution units what to do. [=CPU=]s have many more of these than [=GPUs=], so they can execute individual instruction streams in more complicated ways (out-of-order execution, speculative execution, etc.), leading to much greater performance for each individual instruction stream. ˛* Storage: [=GPUs=] have much smaller cache sizes and available RAM than [=CPUs=]. However, RAM bandwidth for [=GPUs=] typically exceeds the bandwidth of that of [=CPUs=] many times over since they need a fast constant stream of data to operate at their fullest. Any hiccups in the data stream will cause stuttering in the operation.˛˛In the end, [=CPUs=] can execute a wide variety of programs at acceptable speed. [=GPUs=] can execute some special types of programs far faster than a [=CPU=] can, but anything else it will execute much slower, if it can execute it at all.˛˛!!The Future˛˛[=GPUs=] today can execute a lot of programs that formerly only [=CPUs=] could, but with radically different performance characteristics. A typical home [=GPU=] can run hundreds of threads at once, while a typical home [=CPU=] can run two to four. On the other hand, each [=GPU=] thread progresses far more slowly than a [=CPU=] thread. Thus if you have thousands of almost identical tasks you need to run at once, like many pixels in a graphical scene or many objects in a game with physics, a [=GPU=] might be able to do work a hundred times faster than a [=CPU=]. But if you only have a few things to do and they have to happen in sequence, a [=CPU=]-style architecture will give vastly better performance.˛˛Rendering graphics is not the only task that meets the requirements for processing efficiently on a [=GPU=]. Many tasks in science and applied mathematics involve massive numbers of vector and matrix operations that [=GPU=] are ideal for solving. This has given rise to the field of GPGPU (general purpose [=GPU=]) computing. Most modern supercomputers use [=GPU=]s to perform the brute force parts of scientific computations - and to the chagrin of gamers, mid-to-late [=2017=] saw a major shortage of medium / high-end gaming [=GPUs=] due to the advent of cryptocurrencies, causing cryptocurrency miners to buy them in bulk for their mining rigs, doubling or even tripling retail prices. Retailers did wise up, and limited purchases to one card per person, but the price gauging lasted a good full year before going back down to normal around August [=2018=].˛˛----


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