Issuing instructions out of order in data processing

To implement an early data dependency resolution mechanism for a high-performance data processing system that utilises out-of-order instruction issue, an instruction cache and a register-dependency cache are provided. The instruction cache has multiple cache lines each capable of storing multiple instructions 50. The register-dependency cache contains an identical number of cache lines each capable of storing an identical number of register-dependency units 52 as there are instructions in each of the cache lines within the instruction cache. In a single processor cycle, a group of register-dependency units 52 are fetched from the register-dependency cache. All register-dependency units that have no forward data dependency within the group of register-dependency units are identified and translated to its respective instruction utilising a corresponding cache line within the instruction cache. All of the translated instructions are issued within a next processor cycle. Since each register-dependency unit 52 has fewer bits than an instruction 50, more of them can be fetched per processor cycle.