https://rpcs3.net/quickstart
64-Bit Windows or Linux OS
CPU with SSSE3 support
A GPU with OGL 4.3 support (Vulkan and DX12 are also available)
That's it, to 'run' the emulator but depending on your PC and/or the game you might have one frame per second, if at all.
If will take several months and probably years till the emulator and the hardware is at a point you can play most PS3 titles at their native framerate and without image artifacts.
But Demons Souls seems to run 'perfectly' with an 7700K:
https://www.youtube.com/watch?v=tG98QH0RBJQ