What Is A RCD?

A registered clock driver (RCD) chip, or simply known as a “register,” is a critical component of RDIMMs. Its main function is to first receive the instructions or commands from the CPU before sending them to the memory modules. The RCD serves as a “mediator” between the CPU and the DIMM — the data signal stays on the RCD for one clock cycle, and then transfers from the RCD to the DIMM on the rising edge of the next clock signal. This results in instructions taking one CPU cycle longer, but the buffering reduces the strain on the CPU’s memory controller and helps reduce impact on signal integrity.

A critical component of RDIMMs, a registered clock driver (RCD) chip, also known as a “register,” plays a vital role in memory operations. Its primary function is to receive instructions or commands from the CPU before transmitting them to the memory modules. Acting as a mediator, the RCD ensures smooth communication between the CPU and the DIMM.

When an instruction is received, the data signal remains on the RCD for one clock cycle. It is then transferred from the RCD to the DIMM on the rising edge of the subsequent clock signal. Although this process adds an extra CPU cycle to the instructions, the buffering provided by the RCD alleviates strain on the CPU’s memory controller and preserves signal integrity.

The inclusion of RCDs in RDIMMs is crucial due to their ability to maintain consistent memory speed, even under heavy workloads. Unlike speed-focused applications like gaming, enterprise systems and server applications require sustained performance along with high capacity and enhanced reliability features, all made possible by the presence of RCDs in DDR4 memory modules.

The diagram below illustrates the communication flow, where the CPU first interacts with the RCD on each module, which then establishes communication with the memory chips on the dynamic random access memory (DRAM) module.

By understanding the significance of RCDs in RDIMMs, you can appreciate their role in reducing strain on the memory controller and ensuring uninterrupted performance in enterprise systems and servers. Upgrade your memory configuration with RDIMMs to benefit from their buffering capabilities and achieve optimal memory operations in demanding computing environments.