We review some tests of the O-brane and instanton matrix models based
on comparing long-distance interaction potentials between branes and t
heir bound states (with 1/2,1/4 or 1/8 of supersymmetry) in supergravi
ty and in super Yang-Mills descriptions. We first consider the supergr
avity-SYM correspondence at the level of the leading term in the inter
action potential, and then describe some recent results concerning the
subleading term and their implications for the structure of the 2-loo
p F-6 term in the SYM effective action.