I suppose it depends how exact you are in defining 'same calculation' -- two possible causes of inconsistency are: * FP means the rules of algebra do not hold,

I suppose it depends how exact you are in defining 'same calculation' -- two possible causes of inconsistency are: * FP means the rules of algebra do not hold, so if the calculation is done in a different equivalent form, you can get a different result. * With Intel's old FPU unit, if a value is written to memory rather than staying in registers you can get a different result.