Question

I’ve been searching for the major differences between a CPU and a GPU, more precisely the fine line that separates the cpu and gpu. For example, why not use multiple cpus instead of a gpu and vice versa. Why is the gpu “faster” in crunching calculations than the cpu. What are some types of things that one of them can do and the other can’t do or do efficiently and why. Please don’t reply with answers like ” Central processing unit ” and ” “Graphics processing unit”. I’m looking for a in-depth technical answer.

Answer 1

GPUs are basically massively parallel computers. They work well on problems that can use large scale data decomposition and they offer orders of magnitude speedups on those problems.

However, individual processing units in a GPU cannot match a CPU for general purpose performance. They are much simpler and do not have optimizations like long pipelines, out-of-order execution and instruction-level-parallelizaiton.

They also have other drawbacks. Firstly, you users have to have one, which you cannot rely on unless you control the hardware. Also there are overheads in transferring the data from main memory to GPU memory and back.

So it depends on your requirements: in some cases GPUs or dedicated processing units like Tesla are the clear winners, but in other cases, your work cannot be decomposed to make full use of a GPU and the overheads then make CPUs the better choice.