What's the Difference between UDIMMs and RDIMMs?

As we discussed in yesterday's CES 2024 coverage article, Viper Gaming's performance memory lineup will stay on the cutting edge with the addition of the Viper OC RDIMM DDR5 in the near future. This will mark the first RDIMM DDR5 memory modules ever produced by Viper Gaming. 

When it comes to memory, there's a lot to learn about the different DIMMs available in today's market and what needs and advantages they offer. Today, let's discuss some of the key differences, uses and functions that separate RDIMMs and UDIMMs. 

An Overview on UDIMMs

UDIMM, or Unbuffered (also called "Unregistered") Dual In-line Memory Module, is the memory type most gamers will be familiar with. UDIMMs are the most common memory type for the fact that they offer the most simplicity with consumer-grade systems and components.

Compared to that of RDIMMs (and LDIMMs), UDIMMs are directly connected to a system's memory controller and possess a plug-and-play capability. This allows for operation without any timing adjustments and strong performance with compatible systems; however, this will also result in comparatively lower capacities and speeds than some RDIMMs due to increased electrical load compared to RDIMMs. This is a big part of why UDIMMs are common with memory well suited for gaming, such as the Viper Xtreme 5, Viper Elite 5 and Viper Venom DDR5 modules. 

An Overview on RDIMMs

RDIMM, or Registered Dual In-line Memory Module, is a memory type that may be unfamiliar to some. RDIMMs are memory modules that are often designated for heavier server-grade workloads that require a great deal of power.

One essential part to RDIMMs is their inclusion of a buffer on the PCB in between memory modules and a system's memory controller. This buffer is often called a registered clock driver chip, or simply register, and acts as the receiver to send commands between memory modules and memory controllers. As a result of this separation, RDIMMs can offer higher memory capacities and sustain higher workloads and amounts of power due to less electrical load on the controller. RDIMMs will also require a more specific motherboard built for RDIMM performance, as it doesn't possess the same plug-and-play capability as standard UDIMM. 

What are the Main Differences to Remember?

There are a good amount of difference between the two types of performance memory. Perhaps the most distinct difference between UDIMMs and RDIMMs is their system functionalities. Due to their performance as both unbuffered and buffered modules, UDIMM modules will be found in a vast majority of consumer-grade systems due to their RAM needs. However, RDIMM modules will often be utilized for server-grade required performance for high levels of computing power. 

Another key difference between UDIMMs and RDIMMs is their respective read and write cycles. Due to the buffer found in RDIMMs, they will require an additional clock cycle as opposed to more instantaneous cycling on unbuffered memory. Despite longer cycle times, RDIMMs make up for this in reduced electrical load to keep systems steady.  

Both UDIMMs and RDIMMs will commonly possess features to ensure data correction, but both can utilize this technology in different ways. For UDIMMs, there are many that offer features like On-die ECC that help with single-bit errors and detecting multi-bit errors, such as Viper Gaming's Viper Venom DDR5. With RDIMMs, these memory modules contain more circuitry, power and space for more advanced single and multi-bit error correction, leading to more complex correction in server environments. 

Finally, in terms of performance and overall power sustainability, RDIMMs also run at a much higher voltage input than UDIMMs to represent the increase in performance. RDIMMs (and some LDIMMs) require 12V input as opposed to the required 5V input for UDIMMs. 

Ultimately, both RDIMMs and UDIMMs serve strong functions for different systems that can be important to discern. Even still, Viper Gaming's commitment to the highest quality and consistency of performance memory will always remain the same in any kind of DIMM.