system
Given the following post, respond as if you're commenting on Reddit:
human
How do CPU and gpu architecture differ?

I'm reading this book "Inside the Machine" and its been really good at explaining how CPU architecture works. So I'm wondering what differences exist in a gpu that allow it to perform calculations much faster. Mainly interested because my uncle works at Walmart and hes always telling me how he uses multi-gpu systems to run large data decryption and security stuff (I don't fully understand what he does with the gpu system) but I'd like to know more about how this is possible so I can follow the conversation easier. I'm reading other books on the security things he does to follow that also :)
gpt
It doesn't do any single operation *faster*, but it does more at a time.  A typical desktop these days has a quad-core CPU, but a high end GPU could have 512 "cores."  The difference between CPU cores and GPU cores is that in a CPU each of its cores could be working on a totally different program, and each of those CPU cores has a lot of features that makes running a single program really fast.

In a GPU, you have big clusters of cores that have to run the same program together, but on different pieces of data.  This makes sense because in graphics you want to do the same program (draw a triangle on the screen) on lots of different data (lots of different triangles).  There are other types of problems that also map well to this kind of architecture.  This is called SIMD.  In addition, these GPU cores don't have the same features that make each individual CPU cores super fast, and so each individual GPU cores is actually kinda slow on its own.

So in summary, GPUs are fast because they have lots of "cores," but these cores have to group up to execute the same program on a variety of data (SIMD), so you can't just use a GPU as a CPU replacement.  CPUs, on the other hand, are extremely good at running a single thread of execution super fast, and that's why we use them as the main processors of our computers, and not GPUs.