The "floating point" support that's in 6502 BASIC ROMs is not real IEEE 754 floating point though, see https://en.wikipedia.org/wiki/Microsoft_Binary_Format So it shouldn't be used to replace that, though of course one can use it for other purposes with some care. (It goes without saying that this is not hardware floating point, so the only potential gain from piggybacking on these ROM routines will be some saving in code size.)