Systems and methods for processing quality-of-service (QoS) information of memory transactions are described. In an embodiment, a method comprises receiving identification information and quality-of-service information corresponding to a first or original memory transaction transmitted from a hardware subsystem to a memory, receiving a given memory transaction from a processor complex that does not support quality-of-service encoding, determining whether the given memory transaction matches the original memory transaction, and appending the stored quality-of-service information to the given memory transaction in response to the given memory transaction matching the original memory transaction. In some embodiments, a system may be implemented as a system-on-a-chip (SoC). Devices suitable for using these systems include, for example, desktop and laptop computers, tablets, network appliances, mobile phones, personal digital assistants, e-book readers, televisions, and game consoles.