Siemens Energy has commissioned an extensive multiyear experimental and numerical (computational fluid dynamics (CFD)) project to improve its ability to design for and predict compressor stall. The experimental test rig is a half scale six stage axial compressor. The goal of this work is to provide insight into how best to predict the compressor performance map and in particular the stall point by applying state-of-the-art multiple blade row CFD simulation tools. A preliminary CFD analysis quantified numerical, model, and systematic error on the first stage of the compressor. Subsequent steady (mixing plane) and transient (time transformation) CFD simulations of the entire six stage compressor are compared to each other and to experimental data. Both the steady and transient simulations are shown to be computationally efficient and in very good agreement with the experimental data across the full performance map, up to stall inception on multiple speedlines. Physical explanations of the key flow features observed in the experiment, as well as of the differences between the predictions and experimental data, are given.