Semiconductor memory stacks connected to processing units and associated systems and methods

A semiconductor memory stack connected to a processing unit, and associated methods and systems are disclosed. In some embodiments, the semiconductor memory stack may include one or more memory dies attached to and carried by a memory controller die-e.g., high-bandwidth memory. Further, a processing unit (e.g., a processor) may be attached to the memory controller die without an interposer to provide the shortest possible route for signals traveling between the semiconductor memory stack and the processing unit. In addition, the semiconductor memory stack and the processing unit can be attached to a package substrate without an interposer.