Disclosed embodiments relate to atomic memory operations. In one example, a method of executing an instruction atomically and with weak order includes: fetching, by fetch circuitry, the instruction from code storage, the instruction including an opcode, a source identifier, and a destination identifier, decoding, by decode circuitry, the fetched instruction, selecting, by a scheduling circuit, an execution circuit among multiple circuits in a system, scheduling, by the scheduling circuit, execution of the decoded instruction out of order with respect to other instructions, with an order selected to optimize at least one of latency, throughput, power, and performance, and executing the decoded instruction, by the execution circuit, to: atomically read a datum from a location identified by the destination identifier, perform an operation on the datum as specified by the opcode, the operation to use a source operand identified by the source identifier, and write a result back to the location.