Thinking of upgrading your memory? You can buy RAM with up to four 64-bit wide areas or ranks, with single-rank and dual-rank RAM being widely available.
In this article, we’ll compare single and dual-rank RAM to help you understand the difference between these two types of RAM, how to identify them, and which one is best for you.
What is Single-Rank RAM?
Single-rank RAM is a Dual Inline Memory Module (DIMM) or, more simply, a memory stick with a single set of memory chips to be accessed for read and write memory functions on your computer. Alternatively, the memory stick may carry memory chips on both sides of the module that are accessed as a single rank when reading and writing to the memory.
You can determine if a memory stick is single-rank by checking the information sticker it carries. Single-rank memory is identified by 1Rx along with the amount of memory in gigabytes (e.g. Rx8/1Rx8/1Rx16).
RAM with a single-rank arrangement has a 64-bit width. As the memory controller addresses only one rank at a time, single-rank memory is theoretically faster than dual-rank memory, which has to be accessed one rank at a time.
What is Dual-Rank RAM?
Dual-rank RAM is a memory stick that carries two sets of memory chips on it rather than one. This type of multi-rank memory can accommodate an increased memory density, 2 rows of 8 gigabits of RAM (16 gigabits), compared to a single row of 8 gigabit RAM.
On a RAM module label, you’ll see dual-rank RAM denoted as 2Rx, followed by the amount of memory in gigabytes (2Rx4 or 2Rx8).
Dual-rank memory has a configuration with a 128-bit width, compared to the 64-bit width of single-rank memory. But, because the memory channel is 64-bit wide, the memory controller can access only one memory rank at a time for its read/write functions, potentially making dual-rank RAM slower than single-rank RAM despite its increased density and bandwidth.
What’s the Difference Between Single and Dual-Rank RAM?
The primary difference between single and dual-rank RAM is the physical arrangement of the memory cells on the module. The following two factors are key determinants of the number of ranks provided on a memory module:
1. RAM Technology
Certain RAM technologies and generations are more likely to be dual-rank. For example, Double Data Rate 4 Synchronous Dynamic Random-Access Memory (DDR 4), a standard in personal computing, is usually dual or multi-rank. This preference is because each memory chip holds one gigabit of storage and is arranged in two rows of eight on a dual-rank memory module.
2. RAM Size
Large amounts of single-rank storage are also available; for example, up to 16 GB in a single rank on Ballistix Max memory modules from Crucial. For beyond 8 GB, RAM is going to be arranged in a multi-rank format.
Single vs. Dual-Rank RAM Performance Differences
You may think that dual-rank RAM automatically outperforms single-rank RAM because of its greater volume and density of RAM. However, the memory controller, the digital circuit that manages the exchange of data with the RAM module, can only access one rank at a time. This is irrespective of how many ranks of memory are present.
This means that single-rank RAM can have an advantage as the memory controller deals with a single set of memory chips and does not have to run through sequential ranks to access the data it needs.
Multi-rank memory can increase its efficiency by using rank interleaving, a process where the second rank does not become redundant but undergoes its refresh cycle while the memory controller accesses the first rank. The pipelined refresh cycles are key to reducing memory response times and overall latency and give dual-rank RAM a performance advantage.
With fewer memory IC chips on board, single-rank RAM consumes less energy and generates less heat, making them potentially more stable than dual-rank RAM. This stability makes them a preferred RAM format for overclocking, the practice of running the clock rate of CPU at a higher rate than the manufacturer specification.
Single vs. Dual-Rank RAM: A Side-by-Side Comparison
|Single-Rank RAM||Dual-Rank RAM|
|What is it?||Configuration of random access memory (RAM)||Configuration of random access memory (RAM)|
|Primary Use||Storage of temporary system files||Storage of temporary system files|
|Technologies Influenced||DRAM IC Chips||DDR, DDR2, DDR3, or DDR4|
Similarities and Differences
- Single and dual-rank RAM are both composed of DRAM chips on a DIMM (RAM stick).
- JEDEC standardizes both memory formats.
- Single and dual-rank RAM are both used as volatile memory for the normal function of a contemporary computer or laptop.
- Single and dual-rank RAM will lose stored memory if their power supply is interrupted.
- Each ‘rank’ or ‘row’ is either 64 or 72 bits wide.
- A memory controller accesses both types of RAM for read and write functions.
- The memory controller can only access one rank of memory at a time, whether single or dual-rank.
- Single-rank RAM comprises a single set of memory chips in the RAM module. Dual-rank RAM comprises two sets of memory chips.
- Single-rank RAM has lower energy consumption than dual-rank RAM.
- Single-rank RAM has lower heat emissions than dual-rank RAM.
- DDR RAM generations are dual-rank or more.
- Dual-rank RAM is denser than single-rank RAM.
- Dual-rank RAM can carry a greater number of memory chips than most single-rank RAM modules.
- Dual-rank RAM can use interleaving to speed up data access by the memory controller.
What is Single-Rank RAM Used For?
Both single and dual-rank RAM are used as short-term memory, handling the working data and temporary files the operating system (OS), browser, and software applications require to function. You can expect single-rank RAM to provide fast and easy access to the data required for loading apps, browsing the internet, streaming, and gaming.
Single-Rank RAM and Overclocking
Single-rank RAM has a niche application in overclocking, with a reputation for being able to be overclocked further than dual-rank memory. Single-rank RAM can be used for this purpose optimally in T-topology motherboards. These premium motherboards offer greater RAM compatibility and you can run up to 4 modules of single-rank RAM simultaneously.
Single-Rank RAM and Gaming
Single-rank RAM of sufficient size can support fast and responsive gaming, especially if used in a T-topology motherboard. However, objective, ‘real-world’ testing has shown that dual-rank RAM delivers better gaming performance.
Does Single-Rank RAM Need to Be Upgraded?
Upgrading single-rank RAM to dual-rank RAM has the benefits of greater memory density and bandwidth. Dual-rank RAM has more capacity and is often a more cost-effective choice. The interleaving of dual-rank RAM delivers a notable uplift in efficiency because each rank can take turns to work while the other is being accessed.
Performances Gains with Multi-Rank RAM Are Limited
Beyond dual rank, the efficiency gains are far less marked. Quad-rank RAM carries four ranks. Servers mainly use it, and real-world testing has shown that it does not deliver a marked uplift in performance when compared to dual-rank RAM for personal computing.
Multiple ranks can occupy the CPU with a variety of administrative processes, creating a drag and potentially reducing the overall clock speed.
Rather Than Upgrading Memory Rank, Consider Upgrading the Memory Channel
Increasing the number of memory channels delivers a far greater boost in performance than increasing memory rank.
A memory channel provides a dedicated conduit for data exchange between the memory controller and the memory module. Increasing the number of memory channels from single-channel to dual-channel means you can achieve simultaneous access to multiple memory modules, massively increasing bandwidth.
Single vs Dual-Rank RAM: 6 Must-Know Facts
- Single-rank and dual-rank RAM are both types of DIMMs (Dual In-line Memory Module).
- Within a memory rank, all memory chips connect to the same module for simultaneous access.
- A single memory controller will access different memory ranks sequentially.
- Some memory controllers can only support a specified number of ranks. Too many ranks in a memory channel can cause excessive loading and diminish performance.
- Dual-rank RAM uses interleaving to enhance its performance.
- Quad-rank (four ranks of RAM) and even octal-rank (eight ranks of RAM) RAM is available.