Less cache, different architecture, no dual channel ram, all these contribute to the fact that it's a horrible CPU when compared to a regular low end CPU but for the price it's a nice budget CPU.
However, I stand by what I say:
Spend another 50-100 pounds for s939 and it's a world of performance difference.
The Athlon 64 3700+ SD is a great CPU, although a little off for its cost per performance.