Dual Rank RAMWhat the Dual Rank mean?
One such aspect is memory ranks. We’ll be looking into how it affects your work and answer a few common questions like:
- How can you tell whether your current RAM is single or dual rank?
- How much does it impact your performance?
- Is it worth replacing your memory for either single or dual rank options?
What Are Memory Ranks?
Each memory module has a set of DRAM chips that are accessed when writing or reading information. This is what the independent standardization body, JEDEC, has named a “rank.” These memory chips, or ranks, can either be placed on one side of a memory module or both sides.
A single rank configuration refers to a data block (set of memory chips) that is 64 bits wide (72 for ECC memory, which houses 8 additional bits for error checking). In other words, it’s a single set of memory chips or a single memory bank. Dual rank modules will have two of these data blocks and are, therefore, 128 bits wide. Note – As the diagram above shows, some memory modules CAN have chips on both sides but still be single rank.
Quad rank and even octa rank modules also exist, with four or eight 64-bit wide data blocks, respectively. These are usually reserved for higher-end memory modules with large storage sizes per stick.
Many current DDR4 16 GB sticks are dual rank because most IC chips can hold 1 GB of storage. However, Crucial’s higher capacity RevB chips do allow up to 16 GB storage in a single rank (used in their Ballistix Max memory modules). Since you can have a single rank 8 GB or even 16 GB module, both dual rank or quad rank 32GB memory sticks are possible. A DDR4 32 GB single rank memory module does not exist at the moment. But as technology advances, we may see those as well.
Single Rank vs. Dual Rank – Benefits & Drawbacks
So what are the advantages and disadvantages tied to these memory rank configurations? Let’s begin with dual rank memory. Although a RAM module may have two or more ranks per stick, the memory controller can only access one at a time. So, doesn’t that make the second rank redundant?
Dual Rank Advantage
Not exactly. One memory bank can be accessed by the CPU, while the other can undergo a refresh cycle (readying itself to be accessed). This process, called Rank Interleaving, is similar to SDRAM Bank Interleaving. The masking and pipelining of refresh cycles usually results in better performance for CPU-intensive applications, as it reduces memory response times.
Single Rank Advantage
There are certain applications that may be affected by the latency caused by having the memory controller run through multiple ranks instead of just one. Also, because Single Rank (SR) DIMMs have half as many chips, they produce less heat and can be more stable than Dual Rank (DR) modules. This is also what makes them a popular choice for overclocking enthusiasts.