The new casting rules for casting to xs:float say:

if E exceeds 104 (the maximum exponent value in the value space of xs:float) 
then TV is the xs:float value INF or -INF depending on the sign of M.

if E is less than -149 (the minimum exponent value in the value space of 
xs:float) then TV is the xs:float value positive or negative zero depending on 
the sign of M


Note that certain architectures such as the Intel x86 architecture allow float 
values with larger exponent values. We should not penalize such architectures 
and allow them to represent larger and smaller xs:float values before 
switching to INF/-INF.