In this paper we examine some of the environmental conditions that have to be considered when comparing the performance of GPU’s to CPU’s. The range of these considerations varies greatly from the differing ages of the hardware used, to the effects of running the GPU code before the CPU code within the same binary. The latter of these has some quite surprising effects on the system as a whole. We then go on to test the different hardware performance at matrix multiplication using both their basic linear algebra libraries and hand coded functions. This is done while respecting the considerations we have described earlier in the paper, and addressing a problem that with the use of the Intel MKL library cannot be argued to be unfair to the CPU.