jimmysmitty :
It seems too good to be true for a die shrink. I can see double the cores doubling performance but halving the energy use while increasing cores? Seems too good to be true.
It's halving the energy -per instruction-. That metric wouldn't increase with the number of cores, because an instruction will only execute on one core. So they calculate it using the maths.
Also, the CPU probably has some amount of fixed overhead that will get divided by the number of cores in order to calculate the energy per instruction so I could see at least one way where increasing the number of cores could improve efficiency overall.
So if there's two processors with the same power draw, but one manages to double the number of identical cores within that envelope, then the amount of power per instruction will be halved in the processor with double cores (because it is performing twice as many instructions).
Which is still really good for a process shrink. If I remember correctly, the 28nm to 14nm shrink only improved efficiency by about 30% instead of the 50% AMD is claiming for 14nm to 7nm.