AMD's Ryzen Threadripper 2990WX may have a legitimate claim to being the world's fastest desktop CPU, but it's also $1800. Even for a high-end desktop part, that's rather pricey for anybody who's not making money with those CPU cycles, and those 32 cores and 64 threads don't benefit every application. The 2990WX is outstanding when a program can yoke every one of its cores and threads, but our tests suggest most apps on the desktop hit the diminishing-returns point in the scaling curve around 16 cores and 32 threads.