A system and method for instrumenting the execution of instructions in an out-of-sequence execution machine. Instructions tagged with a preselected instruction identification number (IID) are identified. When an instruction having the preselected IID is encountered, information associated with that instruction is saved as the out-of-sequence execution proceeds. If the instruction completes, the information is stored as a single instrumentation entry in a memory array. If the instruction does not complete, the information is disposed of. The process id repeated for each instruction having the preselected IID until the memory array is full. The storage of instruction information in the memory can be further conditioned on the occurrence of a cache miss or other system conditions.