The Essential Guide to Server RAM: DDR3 vs. DDR4 vs. DDR5

Server RAM (Random Access Memory) is a crucial component of network servers. Simply put, RAM is the short-term memory of your server. It is where your network server keeps track of the data and programs currently in use, which means once your server is powered off, RAM modules will wipe the memory.

Common types of RAM on the market include DDR3, DDR4 and DDR5, so shopping for the right server RAM can be confusing. What's the difference among DDR3, DDR4 and DDR5? Are SDRAM and SRAM the same thing? Read on for more explanation on different kinds of RAM.

 

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What is DDR SDRAM?

When people talk about RAM, they're usually referring to Synchronous Dynamic RAM (SDRAM). The magic in SDRAM is that it synchronizes data transfer between the CPU and memory. SDRAM is what this article discusses, too. Do not confuse SDRAM with SRAM, which stands for Static RAM and refers to the memory used for CPU caches.

DDR stands for Double Data Rate. So DDR SDRAM means that two transfers happen per clock cycle. A newer type of RAM is the updated version on the older type based on the same DDR technology. That's why RAM modules carry the label of DDR, DDR2, DDR3, and so on. Each generation of DDR comes with incremental performance improvements over the older generation.

For most network servers, RAM appears as a stick that can be inserted into the server motherboard. Although RAM generations have almost the same physical size and shape, they are not compatible. You cannot insert DDR4 RAM in a server motherboard that only supports DDR3. Likewise, DDR3 doesn't fit in a DDR4 slot.

DDR3

DDR3 SDRAM has been in use since 2007. It is the higher-speed successor to DDR and DDR2 and predecessor to DDR4 SDRAM. The primary benefit of DDR3 SDRAM over its immediate predecessor, is its ability to transfer data at twice the rate (eight times the speed of its internal memory arrays), enabling higher bandwidth or peak data rates.

DDR3 also covers a wide range of CPU generations, stretching from Intel's LGA1366 socket through to LGA1151, as well as AMD's AM3/AM3+ and FM1/2/2+. It has the same number of pins as DDR2. However, it runs a lower voltage of 1.5 V with a frequency between 400 and 1067 MHz.

Furthermore, DDR3 supports DIMMs of up to 16GB in capacity. A DIMM (Dual In-line Memory Module) commonly refers to a memory stick or RAM stick that consists of a number of memory components attached to a circuit board.

DDR4

DDR4 hit the market in 2014 and took some time to become the most popular RAM type. In 2017, it overtook DDR3 to claim the top spot in RAM market. Since then, DDR4 use has steadily grown to the point where in 2020 it accounted for around 80 percent of all RAM sales worldwide.

Compared to DDR3, DDR4 has higher module density, lower voltage requirements, as well as higher data rate transfer speeds. It operates at a voltage of 1.2 V with a frequency between 800 and 1600 MHz. The DDR4 standard allows for DIMMs of up to 64GB in capacity, compared to DDR3's maximum of 16GB per DIMM.

 

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DDR5

DDR5 was set to hit the market in 2019, but that didn't happen. The standard was actually released in mid 2020. The world's first DDR5 DRAM chip was officially launched by SK Hynix on October 6th, 2020.

Arguably, DDR5 is designed for lower power, higher performance, and more robust data integrity for the next decade of computing. It has a new feature called Decision Feedback Equalization (DFE). DFE enables I/O speed scalability for higher bandwidth and performance improvement.

DDR5 supports more bandwidth than DDR4, with 4.8 gigabits per second possible. It further reduces memory voltage to 1.1V, thus reducing power consumption. Moreover, DDR5 modules incorporate on-board voltage regulators in order to reach higher speeds.

There is a general expectation that most use cases that currently use DDR4 will eventually migrate to DDR5.

DDR3 vs. DDR4 vs. DDR5

As aforementioned, each new generation of DDR SDRAM comes with more advanced features and better performance over the older generation.

They may look almost the same at first glance, but there are some subtle differences. For example, DDR4 modules are slightly thicker than DDR3. Plus, there has been a tendency for the key notch to move closer to the middle during the process of iteration from DDR3 to DDR4. In the DDR5 era, it is closer to the middle, even though it is still slightly to one side.

The table below gives you a holistic picture of the differences in key properties of DDR3, DDR4, and DDR5.

DDR4 vs. DDR3

The following shows major advantages of DDR4 over DDR3.

Faster speeds

Compared to DDR3, DDR4 has faster transfer rates, starting at 1600 MT/s, which outpaces the starting speed of DDR3 by a factor of two. Planned bandwidth increases could take it well beyond 25600 MB/s.

Reduced power consumption

DDR4 is more efficient than DDR3, consuming up to 40% less power and requiring only 1.2V per RAM module. This is a great benefit for network servers, as it provides longer battery life.

Increased capacity

DDR4 supports higher density chips and stacking technologies that allow for single RAM modules with capacities as high as 512GB.

Improved reliability

Before DDR5, DDR4 had been the most reliable DDR SDRAM. With improved cyclic redundancy checks, on-chip parity detection of “command and address” transfers and enhanced signal integrity.

Advantages of DDR5 over DDR3 & DDR4

As the 5th generation of DDR SDRAM, DDR5 comes with more game-changing new features.

Greater starting speed performance

DDR5 debuts at 4800 MT/s while DDR4 tops out at 3200 MT/s, a 50% increase in transfer rate. With more advanced compute platform releases, DDR5 has planned performance increases that will scale up to 7200 MT/s.

Reduced power means increased efficiency

At 1.1V, DDR5 consumes 20% less power than equivalent components of DDR4 at 1.2V. Not only will it conserve battery life in laptops, it also has significant benefits for enterprise servers working around the clock.

 

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On-die ECC improves reliability

On-Die ECC (Error Correction Code) is a new feature of DDR5 designed to correct bit errors within the SDRAM chip. As SDRAM chips increase in density through shrinking wafer lithography, potential for data leakage also increases. With on-die ECC, DDR5 mitigates this risk by correcting errors within the chip, which increases reliability and reduces defect rates.

New power architecture

Power architecture is another major benefit. The power management of DDR5 DIMMs moves from the motherboard to the DIMM itself. DDR5 DIMMs will have a power management IC (PMIC) on DIMM which allows for better granularity of system power loading. With better on-DIMM control of the power supply, the PMIC on DDR5 DIMMs helps improve signal integrity and reduce signal noise.

Is DDR5 Worth it Right Now?

DDR5 is the path forward in the long run, but it takes some time for more consumer-level chipsets, CPUs, and other components to support DDR5. You may be wondering, is DDR5 worth the upgrade? Let's dig into various considerations before you rush to a decision.

Cost

Compared to DDR4, DDR5 is bigger, faster and inevitably more expensive. You will have to figure out the budget if you want to upgrade.

Availability

Intel introduced support for DDR5 in their 12th generation Core processors in November 2021. AMD has not yet released processors which support DDR5 but is expected to include DDR5 support in their next-generation Zen 4 architecture. Obviously, there isn't much choice. Plus, stock is often limited for DDR5, meaning it's not that available.

Motherboard upgrade

DDR5 isn't backward compatible with DDR4, and server motherboards only support one or the other. This limitation means that you need to decide whether you want to upgrade your whole motherboard for DDR5.

In summary, despite all the benefits that DDR5 offers, it is recommended that users do not rush to go to DDR5.