This is ancient history so I might be misremembering, but I think float16 first appeared in NVidia GPUs in the 00s when even GLSL was not yet mainstream and the

This is ancient history so I might be misremembering, but I think float16 first appeared in NVidia GPUs in the 00s when even GLSL was not yet mainstream and the thing to use were the {ARB,NV}_fragment_program* pseudo-assembly languages.