The room-temperature longitudinal piezoresistance of n-type and p-type crystalline silicon along selected crystal axes is investigated under uniaxial compressive stresses up to 3 GPa. While the conductance ($G$) of n-type silicon eventually saturates
at $approx 45%$ of its zero-stress value ($G_0$) in accordance with the charge transfer model, in p-type material $G/G_0$ increases above a predicted limit of $approx 4.5$ without any significant saturation, even at 3 GPa. Calculation of $G/G_0$ using textit{ab-initio} density functional theory reveals that neither $G$ nor the mobility, when properly averaged over the hole distribution, saturate at stresses lower than 3 GPa. The lack of saturation has important consequences for strained silicon technologies.
