Methods, reservation stations and processors for allocating resources to a plurality of threads based on the extent to which the instructions associated with each of the threads are speculative. The method comprises receiving a speculation metric for each thread at a reservation station. Each speculation metric represents the extent to which the instructions associated with a particular thread are speculative. The more speculative an instruction, the more likely the instruction has been incorrectly predicted by a branch predictor. The reservation station then allocates functional unit resources (e.g. pipelines) to the threads based on the speculation metrics and selects a number of instructions from one or more of the threads based on the allocation. The selected instructions are then issued to the functional unit resources.