Rambus Improves DDR5 Transfer Speeds By 50% With New RCD

January 02, 2024 by Aaron Carman

Rambus' latest registering clock driver inches DDR5 memory closer to data center-level performance.

Rambus has announced its latest DDR5 registering clock driver (RCD) that boosts memory transfer speeds for data-heavy applications. With generative AI and other applications stretching data centers to their limits, Rambus' RCD is designed to improve memory performance and continue scaling.


Rambus RCDs

Rambus RCDs allow DDR5 memory to work in a wide operating range, with speeds up to 7,200 MT/s. 

While it is easy to get swept up in CPU performance, the pervasive von Neumann architecture ensures that memory speeds are just as important as CPU speed. This is especially true in advanced AI models, which now require higher DDR5 performance.

DDR5 memory improves the theoretical performance of DDR4 thanks to its new architecture, and the RCDs, like Rambus' latest offering, play a critical role in data-center applications and robust DDR5 DIMMs. 


Server-Grade Stability

In data center DIMMs, the RCD lies between the CPU and the memory and acts as a repeater to maintain signal integrity across the entire operating range of the DIMM. This has several advantages, the largest of which is ensuring that the DIMM exhibits the same performance regardless of the computational load.


RCDs act as a repeater between the CPU and the memory

RCDs act as a repeater between the CPU and the memory, allowing for better stability across a wide operating range.

While consumer applications may not realize the full benefit of an RCD, data-heavy applications such as generative AI or cloud-centric predictive maintenance can greatly benefit from the improved robustness and performance of this device. In addition, removing the direct coupling from CPU to memory can provide many different hardware combinations, giving designers more freedom to select the best CPU/memory combination without needing to worry about compatibility.


Better Transfer Speed

The Rambus Gen4 RCD builds off of its previous generations of clock drivers to support greater transfer speeds. The RCD4-GA0A supports up to a 3.6-GHz clock speed and corresponding 7,200 MT/s data rates. It supports both DDR and SDR buses, with up to two independent subchannels and two ranks per subchannel. The device's low 1.1-V power supply requirements may also reduce power consumption, which can greatly benefit large deployments common in the data center.



The RCD helps to decouple the memory’s data and power

The RCD helps to decouple the memory’s data and power from the CPU and motherboard, providing a better operating point in high or low temperatures or data loads. 

Compared to previous generations of Rambus RCD, the RCD4-GA0A increases transfer speeds for DDR5 DIMMs by 12.5%. Compared to conventional DDR5, however, the Rambus Gen4 RCD represents a 50% improvement in transfer speeds (from 4,800 MT/s to 7,200 MT/s). This ability to move data faster opens the door for more advanced AI models.

The Gen4 RCD is currently in the sampling stage. Interested designers can make use of the RCD in conjunction with SPD and temperature sensors to further improve the performance of next-generation DIMMs.



All images used courtesy of Rambus.