I strongly recommend https://fgiesen.wordpress.com/2011/07/09/a-trip-through-the-... if you're curious about GPU architectures. Though in the 14 (!) years since, a lot has changed still.
In the modern era the 'compute shaders' part of that has become more dominant and lots of fixed function parts of the graphics pipeline have moved to software.
I'd love to see a more modern take on this if someone has run across it.