Nvidia ships quite a bit of Tesla hardware for GPGPU data center use; Amazon just bought a massive shipment of these racks for use through AWS.[1]

What's notable about Nvidia's Tesla offerings is that they sit as a separate 1-2U rack on top of the compute box. The space and power costs of operating Nvidia GPGPUs in a datacenter are nontrivial.

If AMD ships a solid ARM product with some good on-die GPGPU components, that might compete with Nvidia, but otherwise the two are in different spaces even within the server world.

[1] http://vr-zone.com/articles/amazon-orders-more-than-10-000-n...