Beowulf be used with GPU's only?

[jpr27]

I know this is kind of a silly question but I hear about rendering farms, Computer clusters, SLI/Crossfire, etc. and I was wondering if it was possible to use Beowulf (or something similar) to maximize the use of just the GPU's (isolating and combining the power of each GPU) in computers for graphic applications. Now I know you really dont want to lose out on the use of the CPU in the rendering farms due to the loss of some of the applications the CPU can assist in the rendering. It's just a hypothetical question. Anyone have and idea or known if it can or has been done and if so, what program or environment (Linux, Windows, etc.) that would best serve this type of application?