An interval order on an arbitrary set X is said to be representable by a pair (u, v) of real-valued functions on X if x y is equivalent to u(x) ≤ v(y) for all x, y ∈ X. We say that a topology τ on X is completely useful in the sense of an interval order (i.o. completely useful for the sake of brevity) if every upper semicontinuous interval order on the topological space (X, τ) is representable by a pair (u, v) of real-valued functions with v upper semicontinuous. We show that every i.o. completely useful topology on X is also completely useful (i.e., every upper semicontinuous total preorder on (X, τ) is representable by an upper semicontinuous utility function). Further we show that a metrizable topology τ on X is i.o. completely useful if and only if τ is separable.