Differences in Estimation - GARCHFIT and ARMAX

I tried to make a simple time series regression using the function GARCHFIT (with no GARCH terms) and it returned a result substantially different from the result given by the function ARMAX, specially the constant term. I also tried to make the same regression using Eviews and the result was different too. What could be the problem?

Thank you, Priscilla

[Wayne King]

Can you please provide the MATLAB code so we can reproduce your results?