Absolute times to calculate a fixed range of the Mandelbrot set:
Machine Concurrency Language Time
Dual-Opteron Singlethreaded C# \~0.81
Dual-Opteron Multithreaded C# \~0.45
Dual-Opteron Singlethreaded C++ \~0.50
Dual-Opteron Multithreaded C++ \~0.38
XBox 360 Singlethreaded C# \~4.4
XBox 360 Multithreaded C# \~2.1
XBox 360\ GPU Shader\ HLSL\ \~0.05
This isn't even fair because the non-GPU timings are strictly timings of the calculation loop. The GPU timing is actually derived from my frame-rate.
I'm having some trouble getting my shader to run on my desktop (ATI All-In-Wonder with Radeon X800), but will post that number when I can.