I don't know but your peformance is dismal on both..
My cheap Athlon 640 X4 should get about 1/2 the performance of your I7 3770...but its averaging about 99% of your results.
Try A live linux distro with pyrit , just to see if there is something wrong with your ubuntu install?
#1: 'CUDA-Device #1 'GeForce GT 240'': 5169.6 PMKs/s (RTT 2.6) #2: 'CPU-Core (SSE2)': 595.4 PMKs/s (RTT 2.8) #3: 'CPU-Core (SSE2)': 618.9 PMKs/s (RTT 3.0) #4: 'CPU-Core (SSE2)': 625.9 PMKs/s (RTT 2.9) #5: 'Network-Clients': 0.0 PMKs/s (RTT 0.0)