Dual asynchronous and synchronous memory system

Abstract

A computer-system implemented method for dual asynchronous and synchronous memory operation in a memory subsystem includes establishing a synchronous channel between a memory controller and a memory buffer chip. A mode selector determines a reference clock source for a memory domain phase-locked loop of the memory buffer chip based on an operating mode of the memory buffer chip. An output of a nest domain phase-locked loop is provided as the reference clock source to the memory domain phase-locked loop in the memory buffer chip based on the operating mode being synchronous. The nest domain phase-locked loop is operable synchronous to a memory controller phase-locked loop of the memory controller. A separate reference clock is provided independent of the nest domain phase-locked loop as the reference clock to the memory domain phase-locked loop based on the operating mode being asynchronous.