Short version: ARMv5 cores (such as in the tablets, the SheevaPlug and the SmartQ) are scalar - they execute one integer operation per clock.

ARMv7 cores are superscalar - they execute multiple operations per clock (in the case of Cortex A8 that is in the N900 and Snapdragon that is in the N1, maximum two per clock). Since interdependence between instruction does not allow actual execution of two operations every clock, the ratio is about as is expected.