It was a little bit unexpected that Athlon 64 FX and Athlon 64 used the same processor core, despite the architectural differences they have. However, AMD uses the same dies for both processors to unify the production process, just like for Opteron processors. They reduce functionality by disabling certain die features on the hardware level.
In fact, you can easily prove that Athlon 64 FX and Opteron processors are close relatives. Both processors feature the same CPUID. For example, we compared the info provided by the CPUZ utility for Athlon 64 FX-51 and Opteron 246.
And this is what the new Athlon 64 FX-51 (on the left) looks like compared with the Opteron processor (on the right):
Well, it is very pleasing that the today’s Athlon 64 FX-51 announcement also indicates the beginning of mass sales of these processors. However, the price of Athlon 64 FX-51 intended for extreme gaming fans will not strike you as very low. AMD set their retail price at $733.