Distribooted Ray Tracing

Does /prog/ think it's feasible to get more than 1 or 2 frames a second with some old desktop computers I've got sitting around?

A hodge podge, really. I know you have to account for latency, of course, but do you think it would be an okay rough estimate to simply add the frequencies of each core of each machine together for a sort of total power? I've got two quad core machines each around 2.7 GHz, and two older, single core machines, each with clock speed of around 1.8 GHz.