oneplanet4all :
The Power9 feeds data to the NVidia GPUs, which is where the real computing is done. This is pretty much what the i-processors from Intel do as well, only on a much smaller scale... GPUs compute much faster and have greater parrellellism than CPUs. The CPU is for many of todays computation tasks just a data shuffling device and not where the real number crunching takes place...
That's an insulting oversimplification of what software, games and processors does today.
The longest running joke in gaming is actually a good example of how important processing power is. "Can it run Crysis?". The first processor able to handle that game without breaking a sweat is the latest generation Intel Core. For what I assume is to simplify bug fixing and speeding up development, game developers almost always limit their thread-needs to two
One for that GPU-feeding and one for all the NPC/AI/other stuff. That second one is the one this IBM processor would struggle with. They do obviously use more threads, but the other ones are usually not under any particular load. Like, mouse polling, networking and such.