  We explore supersymmetric Type I string-motivated three-family scenarios in
which the Standard Model is embedded within two sets of intersecting D branes
with U(1)-extended Pati-Salam gauge groups. We study a model inspired by the
Shiu-Tye Type IIB orientifold, in which a three-family scenario is obtained by
assuming that the gauge symmetry breaking takes place in two stages; the
Pati-Salam group arises from diagonal breaking of the U(N) gauge groups, which
is then broken to the SM gauge group. We investigate the diagonal breaking
scenario in detail and find that generically there are difficulties involved in
decoupling the exotic Higgs remnants. On the phenomenological side, proper low
energy gauge coupling predictions effectively lead to a ``single brane''
scenario for M_string of order 10^16 GeV. The soft parameters in this limit are
constrained by a well-known sum rule, leading to a distinctive phenomenological
pattern for the low energy mass spectrum.
