The CPU is a mathematician that sits in the attic working on a new theory.

The GPU is hundreds of thousands of 2nd graders working on 1+1 math all at the same time.

These days, the CPU is now more like 8 mathematicians sitting in the attic but you get the point.

They're both suited for different jobs.

The CPU could update the picture that you see on the display, but that's grunt work.

Edit: I don't mean the cores in a GPU are stupid, but their instruction set isn't as complex & versatile as a CPU's which is what I meant.

There's no calculation a GPU does that a CPU cannot, and in the very old days the CPU just wrote to a particular location in memory when it wanted something to show up on screen. The reason you need a GPU is that displays have millions of pixels which need to get updated tens to hundreds of times per second, and GPUs are optimized to do a whole lot of the operations needed to render images all at the same time.

It's sort of like asking why we need container ships when aircraft exist that can carry cargo, and the answer is that the container ship can move a whole lot more cargo at once, even if it has some restrictions on where it can take that cargo.

The CPU is really good at task-switching, doing a bunch of things basically all at once.

They GPU is designed to configure itself to ONE task and to do the same thing bazillions of times per second.

It's like comparing a tractor to a sports car. They're fundamentally different machines.

Think of it this way.

The CPU is like a chef in a restaurant. It sees an order coming in for a steak and potatoes and salad. It gets to work cooking those things. It starts the steak in a pan. It has to watch the steak carefully, and flip it at the right time. The potatoes have to be partially boiled in a pot, then finished in the same pan as the steak.

Meanwhile, the CPU delegates the salad to the GPU. The GPU is a guy who operates an entire table full of salad chopping machines. He can only do one thing: chop vegetables. But he can stuff carrots, lettuce, cucumbers, and everything else, into all the machines at once, press the button, and watch it spit out perfect results, far faster than a chef could do.

Back to the programming world.

The CPU excels at processing the main logic of a computer program. The result of one computation will be important for the next part, so it can only do so many things at once.

The GPU excels at getting a ridiculous amount of data and then doing the same processing on ALL of it at the same time. It is particularly good at the kind of math that arranges thousands of little triangles in just the right way to look like a 3D object.

Computers don't "need" GPUs. It's just that if you have the CPU doing all of the processing for images then there is a whole lot less CPU "time" available to do all the general-purpose stuff a computer does and everything would be slower - including the graphics. GPUs are designed to mathematical processing very quickly and can do graphics processing while the CPU is doing other general-purpose stuff. There are lots of chips on a motherboard doing special purpose stuff so that the CPU doesn't have to do it (that's why phones now have SoC - they put a bunch of special purpose shit on the same die as the CPU).

If we’re talking about a 3D game, the information that the CPU passes to the GPU is stuff like the shape of the objects in a scene, what color or what texture that object has and where they are located. The GPU will turn that into a picture that your monitor can display. The way you go from a bunch of shapes and colors to a picture involves a matrix multiplication, which is something that a GPU can do a lot faster than a CPU.

The CPU is really smart, but each "core," can only do one thing at once. 4 cores, means you can process 4 things at the same time.

A GPU has thousands of cores, but each core is really dumb (basic math, and that's about it), and is actually slower than a CPU core. Having thousands of them though means that certain operations which can be split up into thousands of simple math calculations can be done much faster than on a CPU, for example doing millions of calculations to calculate every pixel on your screen.

It's like having 4 college professors and 1000 second graders. If you need calculus done, you give it to the professors, but if you need a million simple addition problems done you give it to the army of second graders and even though each one does it slower than a professor, doing it 1000 at a time is faster in the long run.

A matrix is a bunch of numbers arranged in a rectangle that is X numbers wide and Y numbers long

So if X is 10 and Y is 10, you have a 10 by 10 square filled with random (doesn't matter) numbers. A total of 100 numbers fill the matrix.

If you tell the cpu you want to add +1 to all of the numbers, it does them one by one, left to right, top to bottom one at a time. Let's say adding two numbers together takes 1 second, so this takes 100 seconds, one for each number in our square

If you instead tell a GPU you want to add +1 to all of the numbers, it adds +1 to all the numbers simultaneously and you get your result in 1 second. How can it do that? Well, it has 100 baby-CPUs in it, of course!

So as others have said a CPU can do what a GPU can do, just slower. This crude example is accurate in the sense that a GPU is particularly well-suited for matrix operations... But otherwise it's a very incomplete illustration.

You might wonder - why doesn't everything go through a GPU if it is so much faster. There are a lot of reasons for this but the short answer is the CPU can do anything the baby-CPU/GPU can, but the opposite is not true.

A computer doesn’t need a GPU.

What a GPU is good at is performing the same task on a bunch of pieces of data at the same time. You want to add 3.4 to a million numbers? The GPU will do it much faster than a CPU can. On the other hand, it can’t do a series of complex things as well as a CPU, or move stuff in and out of the computer’s memory or from storage. You can use the GPU’s special abilities for all sorts of things, but calculations involving 3D objects and geometry is a big one — it’s super useful in computer graphics (why it’s called a Graphics Processing Unit) and games. If you want stunning graphics for games, the GPU is going to be the best at doing that for you.

The CPU talks to a GPU using a piece of software called a “driver”. It uses that to hand data to the GPU, like 3D shapes and textures, and then it sends commands like “turn the view 5 degrees”, “move object 1 left 10 units”, and stuff like that. The GPU performs the necessary calculations and makes the picture available to send to the screen.

It’s also possible to program the GPU to solve math problems that involve doing the same thing to a lot of pieces of data at the same time.

Many many years ago, there were only CPUs, and no GPUs.

Take the ancient Atari 2600 games console as an example. It did not have a GPU. Instead, the CPU would have to make sure that the screen is drawn, at exactly the right moment.

When the TV was ready to receive the video signal from the games console, the CPU would have to stop processing the game so that it could generate and start the video signal that would be drawn on the screen. Then, the CPU would have to keep doing this for the entire screen frame's worth of information. Only when the video signal got to the bottom opposite corner of the screen could the CPU actually do any game mechanics updates.

This meant that the CPU of the Atari 2600 could only spend from memory about 30% of its power doing game processing, and the remaining 70% entirely dedicated to video updates as the CPU would literally race the electron beam in the TV.

So later on, newer generations of computers and game consoles started having dedicated circuitry to handle the video processing. They started out as microprocessors in their own right, eventually evolving into the massively parallel processing behemoths they are today.

They don't need a GPU. Until the 1990s, computers didn't have one at all, unless you count a fairly simple device that reads from a chunk of RAM and interprets it as video data a GPU. Early 3D games like Quake were perfectly fine on these systems, and did all the work on the CPU.

What the CPU sends is a lot of textures, and a bunch of triangles, plus information on how to apply the textures to the triangles.

The CPU could do this but the GPU is a lot faster at certain tasks. Drawing triangles being one such task. Twisting the textures around being another.

Early GPUs just did the texturing. That's the most CPU intensive task.

One explanation I like is comparing cpu with superman and gpu with 1000 normal people. The cpu is powerful and can perform lots of instructions just like superman can lift heavy things easily. Gpu can perform simple calculations parallely just like 1000 children who are taught to do math calculation can outperform even superman or cpu if you can divide a task. The pixels need individual calculation. Cpu is slow because it is a single one or its cores are countable in hands which is doing the task. Gpu on the other hand has a lot of small micro cpu with a lot of core count. 1050 ti has about 768 cuda cores.

The key difference is how the two processors function. A GPU is designed to do the same calculation lots of times at once, though with differing values, while a CPU is designed to do lots of different calculations quickly.

A simple way to think about this logic is that a single object on the screen in a game will be on multiple pixels of the screen at once, and each of those pixels will generally need to do the exact same set of calculations with just different input values (think like a*b+c with differing values for a, b, and c). The actual rendering process does the same idea at multiple levels, where you are typically going to position and rotate the points (vertices) of each object in the same way. It also turns out that this same style of calculation is useful for a lot of other stuff: physics calculations*, large math problems*, and artificial intelligence*, to name a few.

However for general program logic you aren't repeating the same calculations over and over with just different data, but instead need to vary the calculations constantly based on what the user is trying to do. This logic often takes the form of "if X do Y else do Z".

Now, modern CPUs will have some hardware designed to function like a GPU, even if you discount any embedded GPU. Using this is very good if you just need to do a small amount of that bulk processing, such that the cost of asking the GPU to do it and receiving the result will be too expensive, however its no where near as fast as the full capabilities of a GPU.

Beyond those design differences which are shared between dedicated and embedded GPUs, a dedicated GPU has the benefit of having its own memory (RAM) and memory bus (the link between the processor and memory). This means both the CPU and GPU can access memory without stepping on each other and slowing each other down. Many uses of a GPU can see massive benefits from this, especially games using what is known as "deferred rendering" which requires a ton of memory.

As a note, there is no reason you couldn't just do everything with one side, and, in fact, older games (eg Doom) did everything on the CPU. In modern computers, both the CPU and GPU are what is known as Turing complete, which means they can theoretically perform every possible calculation. Its just that each is optimized to perform certain types of calculations, at the expense of other kinds.

* As a note, artificial intelligence heavily relies on linear algebra, as does computer rendering. Many other math problems can be described as such, converting the problem into a set of matrix operations, which is specifically the specialization of GPUs.

Most modern CPUs can do exactly what you are stating, as they have the graphical processing capability right on the chip itself. This is enough for most office or school computers, as well as low powered laptops. Generally, GPUs are needed for more difficult tasks that are beyond the capabilities of what a CPU can handle. For example, a very detailed game or computer graphical design will almost require a separate GPU in the PC. However, there are some CPU models that lack the "graphics chips" or are there but disabled by the manufacturer, generally a cheaper model of a CPU.

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With that being said, if someone was building a budget PC, with very light gaming, you can just get a modern CPU capable of onboard graphics for low end performance.

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Although I feel like your question may be as to why a CPU itself would need *any form* of a graphics unit, even if it is "on the chip" as with many modern CPUs. The CPU, strictly speaking, does computations in and of itself, at a very fast rate. However, it does not have the ability to do the output frequency conversions needed for standards that make the PC capable of connecting to an HDMI, VGA, Displayport etc. It is the same notion that necessitates having system ram, a hard disk, and other peripherals attached to do what you want to do.

Cpu does lots of simple but wildly different tasks, a GPU does complex tasks that it is purpose-built for.

To put this into perspective, a relatively low resolution monitor is 1920x1080 pixels. That is over 2 million pixels that need to be potentially sent 3 numbers (red, green, and blue values) for every frame. One gigahertz is 1 billion operations per second. Rendering 60 frames per second is 60 frames * 3 color values * 2 million pixels = 360 million operations per second -- 1/3 of 1 GHz. Even further, graphics depend on tons of other operations like rendering, lighting, antialiasing that need to happen for every frame that is displayed.

It becomes clear that raw speed is not going to solve the problem. We like fast processors because they are more responsive, just like our eyes like higher frame rates because it is smoother. To get smooth, high frame rate video, we need specialized processors that can render millions of pixels dozens of times a second. The trick with GPUs is parallelization.

GPUs have relatively low clock speed (1GHz) compared to CPUs (3-4Ghz), but that have thousands of cores. That’s right, thousands of cores. They also use larger instruction size: usually 256 bits compared to CPUs’ 64 bits. What this all boils down to is boosting the throughput. Computing values for those millions of pixels becomes a whole lot easier when you have 2,000 “slower” cores doing the work all together.

The typical follow up question is “why don’t we just use GPUs for everything since they are so fast and have so many cores?” Primarily because GPUs are purpose built for the task they were designed for. Although that doesn’t prevent the possibility of general computing on GPUs, we humans like computers to be super snappy. Where CPUs can juggle dozens of tasks without a hiccup, GPUs are powerhouses for churning through an incredible volume of repetitive calculations.

PS: Some software takes advantage of the GPU for churning through data. Lots of video and audio editing software can leverage your GPU. Also CAD programs will use the GPU for physics simulations for the same reason.

The cpu is a handful of college math majors, they are skilled in handling a wide variety of problems and in general are much faster than most at doing those calculations. The gpu is a gymnasium full of 5th gradrs, don't ask them to handle advanced calculus but give them a few thousand basic algebra questions and that mob of students is going to be done way faster than those couple of grad students.

Less eli5 : In general the cpu is deciding what happens on the screen and the gpu is in charge of saying that that looks like. As the one takes a lot of varied calculations and the other is more specialized at just drawing shaped and applying textures to them, but doing it with a ton of cores at once.

When it comes to games the cpu is running the game itself, saying what entity is where and where things are headed. The gpu is constantly trying to draw what the cpu says is there, it loads all the physical assets into its own memory, does all the calculations for how the scene is lit and dumps its result onto the screen. Once it's done with all of that it asks the cpu where everything is again and starts all over.

The cpu contains only a handful or so very powerfull general purpose core to do the work, a modern gpu on the other hand has thousands of less flexible dumber cores that can brute force their way through all the work it takes to generate frame in a modern game. Plus having much faster memory on board the card itself helps when gpu is constantly referencing large texture files and storing information dealing with the current frame its working on.

It could, but then it would have to do everything the GPU has to do, and that would prevent it from doing everything that it has to do, and make it slow down. This is called software rendering.

Furthermore, the GPU and a CPU aren't the same when it comes down to things. Sure, they are both made from millions of transistors (digital switches) that turn on and off billions of times a second, but GPUs are like lots of small houses in the suburb, while the CPU can be tall city scrapers, built to do different things.

The GPU has a highly-specialized set of processors and pipelines that are really good at doing almost the same thing to a set of data really fast and in parallel, whereas the CPU has a more generalized processor that is built to be able to to more that just shader, texture and vertex calculations (those things that are really important to what makes 3D graphics amazing, when properly done).

The CPU does everything else, run a program, interact with the user via inputs, communicate with everything else, like the sound device, the network device, disk storage, memory.

Before, "GPUs" were usually just integrated into the motherboard, they were called "framebuffers" and they did mostly that, "buffer" or store one or two "frames" of data long enough for the scanlines to "draw" the image in the buffer to the screen.

But then people wanted more from video games. They wanted effects, like blending two colors together to make transparency effects from when half of your character was in water.

Sure, you could do it in software, but it could be slow, and as resolutions increased, the time to render stuff on screen became slower. So engineers thought, well why not make a specialized card to do those effects for you? This meant that the framebuffer would now have to have it's own processor, to take care of stuff like transparencies and all, and now the CPU was free to do other stuff, like do more things, handle more stuff to be displayed on the screen.

Soon technology became fast enough so that you could send vertexes (3D points instead of 2D pixels) to the video card, and tell the video card to fill in the 3D points (usually triangles) with color (pixels) that would be displayed on screen, instead of telling it to fill a screen with many flat (2D) pixels. And it could do this 60 times per second.

Then, instead of just filling in trangles with a single color, you could now upload a texture (an image, say of barn wall) to the video card, and tell the video card to use the image to paint in the traingles that make up the wall in your scene. And it could do this for hundreds of thousands, and then millions of triangles.

All this while, the CPU is free to focus on other parts of the game, not waiting for data to load into the video card (by using direct memory access for example), or doing any actual pixel filling. Just sending data and commands over on what to do with that data.

Now imagine, if the CPU had to do everything, it would be huge and complex and expensive and run hot, and if it broke you're have to replace your GPU AND your CPU.

Screens have millions of pixels and need to be updated at least 50 times per second. It is possible to connect a CPU directly to an HDMI cable (I have done that) but that doesn't really leave much time for the CPU to do any other work.

For that reason computers have had dedicated graphics chips for a very long time. In the early days those were fairly simple chips that just shared memory with the CPU. The CPU would put instructions like "blue 8x8 pixel square goes here", "Pac-Man goes there" into memory and then the graphics chip would send the right amount of electricity to the monitor at the right time.

These graphics chips have become more and more advanced and about 25-ish years ago were rebranded as GPUs. Nowadays they are quite generic and can run complicated calculations at phenomenal speeds.

As said above, GPUs are centred specifically on video processing tasks. This is why even if you don't want a GPU you will need a CPU capable of handling integrated graphics. The AMD APU series comes to mind.

>What information is the CPU sending to the GPU that it can't just send to a display

It's a bit like this image. Very much simplified, you can think of the CPU sending information like this

• There are 3 vertices (points) at the x, y, z coordinates (340, 239, 485), (312, 285, 512), (352, 297, 482) that form a triangle.
• The vertices have these and those colors, textures, bump maps, reflective values, opacities etc.
• The camera looks at them from position (112, 756, 912) with this and that angle, viewport, zoom.
• There is a spotlight at (567, 88, 45) with this angle, shape, color, intensity. There is another one at (342, 1274, 1056).

And the GPU will come up with

• What is the RGB color of pixel 1234, 342 on the display.

As others have answered, the CPU could do this, but the CPU is optimized for doing a bit of everything, and the GPU is optimized for doing a lot of floating point (decimal value) calculations in parallel.

The CPU is the brain of your computer. It can do everything.

The GPU is a specialized idiot savant. It can only do one type of thing but it can do it really good.

The GPU is good at a certain type of math problem that is needed to create 3D images.

The CPU can do that sort of math too, but since it isn't specialized for it, it isn't as good at it. The CPU isn't as fast at that sort of thing.

The type of math the GPU does well is sometimes useful for other things too, like mining Crypto or certain types of simulations.

CPU cores each run a different program.

GPU cores all run the same program at the same time, but each core operates on different data. They are much slower and more basic than a CPU core, but also much smaller (because they don't need all of the same parts) so you can have thousands of them. Because of that, you can use them to crunch a large amount of repeated calculations very quickly. This is used for mostly for the per-pixel calculations for your display, but they can be also used for other things too like AI training (or Bitcoin mining if you hate the environment.)

The greatest analogy I heard in that regard is to see the CPU as a couple of professors, each calculating difficult equations, while the GPU is a large group of toddlers each coloring a square.

Of course the professors could also color the squares, but they would just waste their potential since they are able to perform much more difficult tasks. It's simply more efficient to let the couple of professors do the hard work, while the large group of toddlers works on coloring the squares.

A CPU is a dremel: can be used for a lot of different tasks and pretty good at most of them.

A GPU is a chainsaw: far more narrow in what its useful for but far more efficient for that what it is good at.

And while you could cut down a tree with a dremel, there are good reasons to use a chainsaw, especially if you need to cut down a certain number of trees per hour.

Nothing. Your CPU can do everything your GPU can. At like, 1:100000000th the speed. Do you want to play your games at about 1 frame every 3 minutes? Then use your CPU.

Then why have a CPU? Why not just a GPU? Because to make the GPU do the type of math that is needed to draw images very very very very fast, it has to be made poopy at other kinds of math. This isn't a software problem either, it's a hardware problem. IE the little squiggles we etch into crystals to zot electricity through to make the crystal think for us need to be drawn in certain ways to work how we want, and we can't have two doodles overlapping each other.

A CPU can do almost anything, but it's slow because of it. A GPU can do graphics (and certain types of AI work) very very very fast, but can't do anything else quickly (or in some cases, at all). So you need both. Unless you don't give a hoot about fancy graphics and are okay with your computer being able to produce graphics that are on par with 80s and VERY early 90s PC graphics only.

Good question! They should just put some cpu's on gpu's to bypass this and render even faster!

Another point is that even if the GPU would do very little computing, you would need something able to communicate between your screen and your computer. This is similar to external sound cards and network cards, although these are not so common these days because for most users the integrated cards are fine.

TLDR: the gpu is specialized in tasks needed for rendering. That way the cpu doesn’t have to do all the work and can do other tasks instead that the gpu isn’t capable of doing.

My best eli5:

You have two workers. One can do everything but not particularly fast. The other can draw really good but can’t do anything else.

Of course you could have the first worker do everything, but that would be slow. Instead you have the first one do all the story and background, and the second guy just for drawings, so that the first has time For other stuff

A bit more technical:

In a really rudimentary CPU you have a component that adds things together. Now let’s say you want to multiply two numbers. You could do that by simply adding several times.

If you do that you block the component that adds for quite a while. So instead you make a new component dedicated to multiplying. Now you can simultaneously add something while something else is being multiplied.

So you’re dedicating a component to a specific task in order to have more performance. And this goes way further. Anything you gpu does your cpu can too. But it’s like the multiplying: if the cpu does everything the gpu does Them is occupied a lot and can’t work on other tasks.

The GPU has components for tasks that are very common for rendering. So you take the entire workload of rendering an image away from the cpu and shove it onto the gpu. Now your cpu is free to do other things that the gpu can’t.

So yes, you can run a computer with just a cpu. But this cpu would constantly be occupied with rendering, and while its doing that it can’t do other stuff. You end up with a lot less performance.

The CPU is capable but contain a larger set of instructions, this slows things down creating wait times. The GPU has a handful of simple instructions that come in the form of shader programs. It's able to process and reduce wait times due to efficiency

Computers don't need GPUs. Older computers from the 80s sometimes didn't have any GPU, and the CPU was responsible for redrawing what you see on the monitor.

The problem with that is that it costs a lot of CPU time to do so, redrawing all the pixels 50 or 60 times per second.

GPUs started out as nothing more than a helper chip(set) for the CPU, so it wouldn't be doing the pixel pushing, but could do other stuff at the same time.

As what we wanted to see on the screen became more complex GPUs consequently also became more complex. First it was 2D acceleration to improve drawing windows and sprites on the screen, later 3D acceleration for obvious uses.

Or said in one line, CPUs are generalists so they can do the 'anything' computers are known for, GPUs are specialists so the CPU can continue doing generalist stuff, like instructing the GPU to 'draw a rectangle there', 'move the sprite from here to here over X frames', or 'add a sphere to the 3D scene'.

The CPU sends the meshes (set of vertices) and textures (non-uniform colors that go in the area between vertices) to the GPU when the software is loaded. Those are saved in the GPU memory. They can be updated from time to time, but they are changed as rarely as possible.

For each frame, the CPU sends commands to show those meshes by sending their position, axis, and scale, and those textures by sending in between which vertices it should appear. The GPU gets all those objects from memory, put them in the good position, axis, and scale in RGB arrays, and combines them. Combining them includes having only the ones in the front if they are opaque, and doing some addition if they have some transparency. The GPUs can also compute the effects of lights, in particular using ray tracing, to determine the brightness of each pixel.

Here is some extra information: https://computergraphics.stackexchange.com/questions/12110/what-data-is-passed-from-the-cpu-to-the-gpu-each-frame

Computers technically don't "need" a GPU. In fact, early home computers didn't have them. The American NES and Japanese Famicom game consoles were one of the first to have GPU's (then called the PPU).

The main advantages of this are…

1.) The GPU can process graphics information while the CPU handles other tasks, speeding up processing by acting as a digital carpool lane. In systems without this, programmers had to decide how much of a program's processing went to executing code, and how much went to graphics and sound. Time spent on one of these was essentially taken away from the other two.

A common side effect of this is that older programs (particularly games) would frequently only use part of the screen, since fewer pixels or tiles meant less time needed for processing. Some early games on, for example, the Atari, would even remove lines on the left and right sides to further reduce graphics requirements.

2.) Because it only handles graphical data, the GPU can be optimized in ways the CPU can't, allowing it to perform these calculations much faster than simply having, say, a second CPU running. This comes at the cost of being inefficient at, or even unable to perform, other calculations.

I remember reading a webpage/blog post where a 3D render was 30× faster when done with the GPU vs the CPU. This was ten or fifteen years ago.

TL;DR? It allows more data to be processed at once, and optimizes the processing of the particularly complex graphics calculations.

The CPU is a general-purpose computer. It's strength lies in being able to do any kind of calculation. A GPU is a specialized computer that's optimised for the specific task of rendering 3D graphics, and does its job much faster as a result.

CPU can do everything. It's one really smart and hard working guy just going off of endless instructions.

GPU is a collection of smart fast hard working guys all given portions of specific instructions and are told to start working at the same time.

Another analogy - CPU is me remodeling bathroom step by step in an apartment building. When done, I move to next one.

GPU is a bunch of guys all assigned small tasks all located in designated bathrooms in the apartment building.

Which one is overall faster?

Say you want to draw a circle with radius R in location X,Y on your screen. To do this in the CPU you would need to do all the math to figure out which pixels should light up and which should not in order to make the circle, and then send that pixel data to the monitor. This takes a lot of CPU resources and will generally be very slow.

What a GPU does is simplify common operations like this for the CPU. Instead of doing all the math, the CPU can send a command to the GPU to draw the circle with the same parameters, and the GPU will handle it automatically. This will free up the CPU to do other stuff. Additionally the GPU will have dedicated circuits in the chip that can do all the math and draw to the screen much faster than the CPU.

So technically yes the CPU could send direct to the display, but a separate GPU will accelerate a lot of the common math needed to draw the images to the screen.

Compare the author to the painter.

One inspires the other to create visual representation of the numbers and inputs.

A GPU is essentially a second CPU for your computer. The difference is that while a CPU is good at any task you can throw at it, a GPU is really good at exactly one thing – performing the kind of complex mathematical calculations that are used to render graphics. A CPU could technically perform these operations, but it would just be a lot slower at it.

When you are playing a game that has fancy HD graphics and needs to run at a high FPS, the CPU can offload the rendering to the GPU and the GPU sends the final frames to the display directly, resulting in much faster performance.

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A GPU is almost like a separate computer inside your computer suited to one specific task. It's like having a gaming console attached to your motherboard. A CPU can more or less do anything. After all an "integrated GPU" is really just the CPU doing the job of the graphics card as well as its own. The problem is that for most types of use for a PC, you don't need a GPU at all. Office computers, casual users just browsing the web and watching movies, store computers etc don't really need a GPU, because their tasks do not require lots of processing power. Conversely there's some tasks/activities, like gaming, rendering, cad/cam software and others that do require a lot of processing power, a disproportionate amount compared to most other things. So the solution is to have a "separate" computer inside your computer, with its own processors and its own memory, dedicated to those tasks specifically and since software is written around this industry convention, the GPU will perform those tasks more efficiently. Something like a server, used for different tasks, won't have a GPU at all, but it will have multiple CPUs and tons of storage space because that's the kind of resources it needs for its tasks.

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