The worst of this is that internal 80 bit x87 registers are truncated to 64 bit when written to memory. You have essentially no control over when this happens f

The worst of this is that internal 80 bit x87 registers are truncated to 64 bit when written to memory. You have essentially no control over when this happens from the language level. It meant that floating point code was all rather undefined and you got different results on different compilers. As someone who has had to write multi platform numerical code I'm very thankful it's gone from AMD64.