Design space exploration (DSE) is a key ingredient of system-level design, enabling designers to quickly prune the set of possible designs and determine, e.g., the number of the processing cores, the mapping of application tasks to cores, and the core configuration such as the cache organization. High-level performance estimation is a principle component of any system-level DSE: it has to be fast and sufficiently precise. Modern out-of-order architectures with caches pose a significant problem to this performance estimation process, as no simple one-to-one mapping of the number of cache misses and resulting cycle time exists.We present a high-level cache performance-estimation framework for out-of-order processors. Evaluation shows that our prediction method is on average 15 times faster than cycle-accurate simulation, while our estimates only show an average error of below 3.5%, reduce the pessimism of a naive high-level performance estimation by around 66%, and still maintain a high fidelity. Our approach thus enables quick yet accurate performance estimation and extends the applicability of system-level DSE to out-of-order processors with caches.