I have a copy of the ISO C99 standards.

On another forum I found -
<snip>
In fact for languages where the standard specifies that all arithemetic is done internally in double precision (e.g. ANSI C), single precision can run slower than double because of the extra conversions ....<snip>
The thread is discussing preformance differences for single vs double precision.

Anyway I cannot manage to find something in the standard to support this.
I'm guessing it's me.

Are all floats promoted to double by standard? Help.