  We study a quantum corrected SO(6) invariant matrix quantum mechanics
obtained from the s-wave modes of the scalars of N = 4 SYM on S^3. For
commuting matrices, this model is believed to describe the 1/8 BPS states of
the full SYM theory. In the large N limit the ground state corresponds to a
distribution of eigenvalues on a S^5 which we identify with the sphere on the
dual geometry AdS_5x S^5. We then consider non-BPS excitations by studying
matrix perturbations where the off-diagonal modes are treated perturbatively.
To a first approximation, these modes can be described by a free theory of
"string bits" whose energies depend on the diagonal degrees of freedom. We then
consider a state with two string bits and large angular momentum J on the
sphere. In the large J limit we use a simple saddle point approximation to show
that the energy of these states coincides precisely with the BMN spectrum to
all orders in the 't Hooft coupling. We also find some new problems with the
all loop Bethe Ansatz conjecture of the N=4 SYM planar spin chain model.
