  Evans and Pippenger showed in 1998 that noisy gates with 2 inputs are
universal for arbitrary computation (i.e. can compute any function with bounded
error), if all gates fail independently with probability epsilon and
epsilon<theta, where theta is roughly 8.856%.
  We show that formulas built from gates with 2 inputs, in which each gate
fails with probability at least theta cannot be universal. Hence, there is a
threshold on the tolerable noise for formulas with 2-input gates and it is
theta. We conjecture that the same threshold also holds for circuits.
