Operating system laboratory assignments based on bare hardware or detailed machine simulators can be excessively challenging for many students. In the most often used approach, students develop kernels on virtual machines with a much simplified hardware interface. Traditionally this simplification goes so far as to make realistic performance measurement impossible. We propose Vesper, an instructional hardware simulator with a high degree of performance realism. Vesper retains simplicity while providing timing statistics close to that of real hardware. The key to our approach is to provide hardware abstractions that are simple but yet capable of capturing device interactions with major performance impacts. Vesper laboratory assignments allow students to realistically explore the performance consequences of various system designs without the cumbersome aspects of the real hardware interface. Currently we have completed the design and implementation of the Vesper disk drive simulator, reported in a SIGCSE'06 paper.