Probably more than 100x for inference. Not only are you drastically reducing the number of bits and replacing float math with integer math, you can do matrix multiplication with only addition (as pointed out in the BitNet b1.58 paper). Additions require a lot less hardware to implement than multiplication. Adding one-bit or two-bit numbers requires barely any hardware at all. A traditional two-bit adder without carry bit is three xor gates and an and gate.