Curious
In: Technology
They serve different purposes. It’s kinda like saying, why can’t I drive a boat on land, when I can drive a car through a puddle. That being said, you probably could run an operating system on a GPU if it was coded for it, but there’s some stuff it will be really inefficient for
The GPU and CPU have fundamentally different jobs. Anything that needs to be displayed on the screen requires processing by the GPU. The CPU cannot to that. While there are games that primarily use the CPU, they still need to use the GPU. Even just browsing the internet or the files on your computer requires a GPU.
The GPU is really good at vector mathematics, which is why it’s good at interpreting the 3D environment of the game and telling the screen what color to make what pixel. The CPU can’t do that, the CPU does basic math, like addition, multiplication, and logic. While you technically could get a GPU do those tasks, there’s so much power you aren’t utilizing if you treat it like a CPU, so it’s cheaper to have a CPU for all the normal math, and a GPU for all of the complex math.
GPUs have fundamentally different working principle from a CPU. A CPU can execute a long sequence of complicated instructions quickly, but can only handle a few such sequences at the same time.
A GPU can only handle really short sequences of instructions, but can handle several hundred to several thousand such sequences simultaneously.
For regular software, such as web browsers and operating systems, they consist of long sequences of instructions that would not be possible to implement for a GPU. But the rendering of graphics in a game consists of a short task that needs to be repeated a lot, for example calculating light and color for each pixel, each pixel is a short sequence but there are thousands of pixels that can be calculated in parallel. Other tasks such as training machine learning models and mining cryptocurrency are also suitable for running on a GPU.
It’s not the CPU or GPU that powers your computer. It’s the motherboard.
The motherboard manages the whole deal. It provides all the various “channels” of communication across all inputs and outputs.
Obviously you have to plug-in the things that do the major computation work, like a CPU. But the connectors exposed for such things only have limited “privileges”, and there’s an array of other non-CPU/GPU chips that are hard-soldered for many other jobs.
If you made a GPU that could be plugged-in to a CPU slot and provide everything the motherboard expects, it’s no longer a GPU. It’s just another CPU, but one that is not very well suited to the tasks of general computation, such as bootstrapping and loading an Operating System.
The reason for that is well explained by others here – GPUs are built for a very specific job.
GPU can do simple multiplication, in parallel and really fast, a CPU can do a lot more complicated math that a GPU cannot do.
The CPU has a tiny GPU inside it, that’s why you can play low end games on it. Some CPU’s don’t have this and if you try to use it without a GPU you get no picture whatsoever. You can’t even see Windows.
You could in theory make a GPU with a tiny CPU in it but you’d need a special motherboard for it to work plus playing games on a GPU that would be high end enough to have something like this requires a decent CPU that they wouldn’t include inside a GPU.
The CPU’s a Corolla, the GPU’s an F1 car. They’re both cars: they both move you around and have four wheels. But one of them is very specialized to excel at a narrow range of tasks. You could technically take the F1 car into town to get groceries or run the Corolla on a racetrack but you wouldn’t be happy with the results.
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