Chun-ting "Tim" Wang Lee, PhD, is a Signal Integrity Application Scientist in the Electronic Design Automation Group of Keysight Technologies. Wang Lee received his PhD in Electrical Engineering from the University of Colorado at Boulder. He has been focusing on understanding high speed channels and improving simulation and measurement correlation.
In earlier DDR systems, the clock, command, and address signals (here in referred to as C/A) were distributed to multiple DRAMs using a forked topology, in which these signals propagate to all the DRAMs in the system at approximately the same time. The propagation delays on the command and address lines (in such systems) introduced timing skew into the system, limiting the operating frequency of the bus and eventually impacting the performance of these memory systems.
The most notable difference between DDR5 and previous generations is the introduction of decision feedback equalization, a technique used in serial link systems to improve the integrity of received signals. In the wake of the new technology, this short article outlines some of the fundamental signal integrity concepts in the context of DDR5.