FP64 is more like 64 times harder than FP8. Actually the cost is even much higher, because the cost ratio is not much less than the square of the ratio between

FP64 is more like 64 times harder than FP8. Actually the cost is even much higher, because the cost ratio is not much less than the square of the ratio between the sizes of the significands, which in this case is 52 bits / 4 bits = 13, and the square of 13 is 169.