Nothing. Part of computing today is not just the horse power, but, all the artists, drawings, musicians, user interface specialists & getting people with the money and power to make such a device affordable and get general public interest to find all these things useful. This means also fast networking structure like the internet which can communicate between individuals and expand the use of that horse power as well.
You may find a niche R&D lab with specialists doing some fancy math an limited physics experiments, but, it could never expand to the rest of the world and just the materials, manufacturing infrastructure needed just to make a single copy. It's not just the CPUs, ram, dont forget the power transistors, compact low ESR capacitors even for the power supply. Such a computer would be considered a military secret and hidden and used to break foreign cryptography. That's about it.