  The exponential growth of floating point power in graphics processing units
(GPUs), together with their low cost, has given rise to an attractive platform
upon which to deploy lattice QCD calculations. GPUs are essentially many
(O(100)) core chips, that are programmed using a massively threaded
environment, and so are representative of the future of high performance
computing (HPC). The large ratio of raw floating point operations per second to
memory bandwidth that is characteristic of GPUs necessitates that unique
algorithmic design choices are made to harness their full potential. We review
the progress to date in using GPUs for large scale calculations, and contrast
GPUs against more traditional HPC architectures
