For a famous cubic system given by James and
Lloyd, there exist some sufficient conditions such that the system
has eight limit cycles. In this paper, we try to derive by
computers the necessary and sufficient conditions for this system
to have eight limit cycles. In order to find the symbolic real
solutions to semi-algebraic systems where polynomials are Lyapunov
quantities, we transform the equations into triangular systems by
pseudo-division, locate the real solutions of the last equation
and verify the inequalities by the Budan-Fourier theorem. The
necessary and sufficient conditions for the system to have eight
limit cycles are given under a reasonable limitation.