I am currently developing a game mechanic that needs to tick very frequently; as such, it needs to be strictly mathematic, without the use of any conditional statements (in the language of choice, math functions are faster than conditionals).

Essentially, my question is this:

How can I apply a "floor" or perhaps "minimum" to the input value of some parabolic function? E.g. the $x$ in $y = x^{2}$ cannot be less than 80. Anything less would just produce the same $y$ value. However, after $x$ reaches 80 or above, the parabolic function should apply normally.