DDR – Double Data Rate: the benefits of industrial DDR5 RDIMM memory modules

This article originally appeared in the July'22 magazine issue of Electronic Specifier Design – see ES's Magazine Archives for more featured publications.

The memory bandwidth of DDR5 is twice that of DDR4. If the transfer rate is calculated at the initial 4,800Mhz, it is 50% higher than the 3,200Mhz of DDR4. In addition to significant improvements in performance, DDR5 memory has also made good progress in capacity, stability and power-saving efficiency. Enterprise and data centre servers, AI, high-speed computing and other applications are expected to become the early adopters of DDR5 technology in the industrial market.

DDR5 RDIMM industrial server memory, with its excellent performance and reliability, shoulders critical tasks such as increasing the speed of massive data transfers and ensuring that servers operate at optimal workloads.

With this said, what are the differences in technical specifications of DDR5 RDIMMs (registered dual in-line memory modules), which demand special attention during product development? When adopting DDR5 industrial memory, what’s the best way to grasp the advantages and seize the market opportunity?

DDR5 RDIMM server memory modules’ seven key differences to DDR4

1. Dual-channel architecture, double the bandwidth

DDR5 memory is developed with a new channel architecture, providing two sets of completely independent 32-bit sub-channels. Not only does the double bandwidth mode improve overall performance, but it also effectively shortens access latency and improves channel efficiency.

The DDR5 RDIMM server memory has dual 40-bit sub-channels, adding eight bits to the existing 32 bits of each channel to support the use of an ECC (error correction code)-based error detection and correction mechanism. The design of the RCD (registering clock driver) can further reduce the load of the CPU, strengthen the signal integrity and reduce interference.

2. Double the number of bank groups and improved performance

Compared with DDR4, the bank groups of DDR5 memory have increased from four to eight, and the total number of banks has also increased from 16 to 32. This doubling of the number of bank groups helps to increase the amount of data transmitted, thereby optimising the overall core timing parameters. This allows the memory to respond to execution actions at a faster speed and achieve ultra-high performance.

3. Voltage drop means great power savings

The standard operating voltage of DDR5 memory is reduced from DDR4’s 1.2V to just 1.1V, which improves the power saving efficiency by 8%. Alongside this reduction of system power consumption and heat generation (especially in industrial systems), server applications that require 24/7 operation will also enjoy additional power saving benefits.

4. PMIC makes the signal more stable

With the voltage reduced to 1.1V, in order to ensure voltage accuracy for stability during high-speed operations, DDR5 memory also adds power management functions. Instead of the traditional control method through the motherboard, the DDR5 memory is equipped with a power management integrated circuit (PMIC), which can control the system power load with both increased efficiency and an 85% improvement in power conversion efficiency. The technology thereby improves signal integrity and compatibility, and even reduces the cost of the motherboard design for power supply.

In addition, although they both output a working voltage of 1.1V, there are currently two PMIC specifications used in DDR5 memory. Unlike the use of 5V PMICs seen in DDR5 UDIMM (unregistered dual inline memory module) and SODIMM (small outline dual in-line memory module), for server applications, DDR5 RDIMM server memory uses a 12V PMIC. Special attention should be paid to system platform design.

5. Equipped with On-die and Side-band ECC for automatic error correction

In order to achieve higher performance, DDR5 memory has been improved in both capacity and data density. However, the technology scaling may also increase the risk of data errors. DDR5 RDIMM server memory supports On-die and Side-band ECC mechanisms, which can automatically detect and correct data errors in the memory. They provide end-to-end complete protection for the data transmission process and improve memory data fault tolerance, thereby improving data accuracy.

More importantly, this error correction mechanism also contributes to the stable and reliable performance of the system, meeting the reliability, availability and serviceability requirements of server applications for long-term operation.

6. Temperature sensor configuration can avoid overheating

In addition to adopting new components such as RCDs, PMICs and SPD hubs, DDR5 RDIMM server memory also adds a high-precision temperature sensor. This provides detailed memory temperature data to monitor the heat dissipation of the memory in real time. When designing the airflow of the system, the R&D personnel can also calculate the heat dissipation more accurately, therefore avoiding excessive heat accumulation and affecting the stability of the system operation.

7. Same bank refresh function shortens delay time

In DDR4, for a refresh to occur, all banks need to be in an idle state and cannot execute other instructions at the same time. The Same Bank Refresh function of DDR5 memory allows the system to update a specific bank without affecting the access of other bank data, meaning that it greatly reduces overall idle delay and improves system performance.

Preparing for the move to DDR5

The demands of the industrial market for massive data processing and high-perfor[1]mance computing continue to grow, and this is accelerating the need for memory technology upgrades. The introduction of DDR5 technology has also become inevitable. Processor platforms that support DDR5 applications in the market have been launched one after another.

This is a critical moment for users to introduce DDR5 memory and related system platforms. The following three subsections explore some metrics that can be used as a reference for selecting DDR5 industrial memory products in the future.

1. The JEDEC 1.0 mass production version test

In the process of development and testing of DDR5 products, they must comply with the standards formulated by the JEDEC Solid State Technology Association and also be in accordance with the specifications of the mass production version recognised by JEDEC. At present, JEDEC has released the DDR5 RDIMM server memory 1.0 mass production standard.

This means that, when a user selects DDR5 RDIMMs, they should apply special attention to whether the manufacturer has completed the test in accordance with the JEDEC 1.0 standard specification, as this will determine whether the technology is ready for mass production. (At the time of writing, Apacer's DDR5 memory has completed the latest JEDEC mass production version test, and mass production is just around the corner.)

2. Use of high-quality original ICs

In key applications such as the industrial market, servers and data centres, the cost and goodwill lost due to downtime are often too large to measure. These applications cannot bear abnormal risks such as unstable memory quality. Industrial memory modules made with high-quality original DDR5 DRAM ICs (integrated circuits) from major manufacturers have extremely high product reliability and warranty protection, and accordingly, are the first choice for industrial systems.

3. Support for multiple value-added protection technologies

The application scenarios of industrial memory are diverse, and server applications are no longer limited to running in indoor computer rooms with comprehensive environmental control equipment. Addressing the question of how to improve the environmental resistance of DDR5 memory will be the key.

Nevertheless, there are already mature value-added protection technologies available on the market, such as conformal coating, underfill, and Apacer's patented Anti-Sul[1]furation technology, all of which can protect the DDR5 module’s surface from external environmental challenges such as humidity, dust, environmental pollution, vibration, and shock.