[chclau]

For me, one option is to be able to learn processors in depth. You want to understand how one works? You can always emulate it in SW, but on an FPGA you can make them interact with the real world in real time and probe them at the same time, with ready made signal analyzers that the vendors provide, and/or by making your own tools.

Another option, do you want to see by yourself how caching improves code performance? You can make that on an FPGA also.

I have done some time ago a very nice course which is called From Nand to Tetris, that teaches how to go all the way from gates to a processor. My plan for the near future is to implement the NAND2Tetris processor on a Basys 3 board, and make some of the examples I mentioned (like, probing internal registers using HW tools, or seeing by yourself how a cache improves performance). I hope to make some of these things available on my site. I am the OP, but just in case, my website is https://fpgaer.tech