Oh yes I forgot to mention it, you’re absolutely right, Thall’s method for df64 and qf128 gives you double/quad precision mantissa with single-precision exponent ranges, and the paper is clear about that.

FWIW, my own example (emulating doubles/quads with ints) gives the full exponent range with no wasted bits since I’m just emulating IEEE format directly.

Of course there are also bignum libraries that can do arbitrary precision. I guess one of the things I meant to convey but didn’t say directly is that using double precision isn’t export controlled, as one might interpret the top of thi thread, but a certain level of fp64 performance might be.