A better comparison might be dedicated hardware versus virtualized in EC2 than virtualized on stand alone hardware as EC2 is a shared environment.
I understand that technically there shouldn't be much disparity for CPU bound tasks (because most instructions are translated directly), but our benchmarks show a 40x performance hit for heavily CPU bound, single threaded tasks between a large EC2 instance and an entry level softlayer dedicated box (doing computer vision work). Perhaps it's a caching issue caused by Xen and other VMs sharing the hardware or perhaps its the fact that EC2 is built on older hardware that might not support some of the more advanced CPU features. Regardless, core for core on a anecdotal level, we have seen a stunningly large impact by switching to dedicated hardware.
I understand that technically there shouldn't be much disparity for CPU bound tasks (because most instructions are translated directly), but our benchmarks show a 40x performance hit for heavily CPU bound, single threaded tasks between a large EC2 instance and an entry level softlayer dedicated box (doing computer vision work). Perhaps it's a caching issue caused by Xen and other VMs sharing the hardware or perhaps its the fact that EC2 is built on older hardware that might not support some of the more advanced CPU features. Regardless, core for core on a anecdotal level, we have seen a stunningly large impact by switching to dedicated hardware.