  We present a numerical study of autocorrelation functions of a 3D Fully
Frustrated Ising model (FFIM) simulated by spin-flip Monte Carlo dynamics,
finding simple exponential decay for all the temperature above the critical
temperature T_c for the autocorrelation of squared magnetization, and stretched
exponential decay for the energy autocorrelation below a temperature T^* with
T_c < T^* =< T_p where T_p is the Kasteleyn-Fortuin and Coniglio-Klein
percolation temperature. The results are compared to those on 2D FFIM to give
insight on the relevant mechanism in the onset of stretched exponential
relaxation functions.
