Common Memory Specifications Overview

There are many words and acronyms associated with computers and servers that can lead to confusion. If you’re trying to upgrade your system and a slow computer has pushed your frustration to the limit, the last thing you want to do is have to figure out what specific memory and storage tech terms mean. Here are some frequently asked questions to help you learn more and help you find the best possible upgrade.

These three terms are often used interchangeably. ‘RAM’ stands for random access memory and ‘DRAM’ stands for dynamic random access memory.

A form factor is the physical form, or physical dimensions, of the module. UDIMM, or unbuffered dual in-line memory module, is the most common form factor of memory that desktops use. Laptops or other small systems use SODIMMs, or small outline DIMMs, which have fewer pins (the gold edges on the bottom of the module) and are physically shorter than UDIMMs. Servers use a variety of different standards in addition to form factors, depending on how the server is used (RDIMM, LRDIMM, FBDIMM, ECC UDIMM, ECC SODIMM, NVDIMM, etc.).

The total capacity is the total memory the module or kit of modules provides in gigabytes (GB). Having more GBs of RAM is better because your system can quickly run and use more active data.

The amount of data that can be transferred from the memory to the CPU in a given amount of time. Speed is measured in megatransfers per second (MT/s), and in general, more speed is better.

Voltage is how much power the module consumes. Higher voltages mean the system uses more energy and can also lead to higher system temperatures, which can negatively affect your system’s health.

The total amount of data, not just speed, the module is able to process at once. The higher the bandwidth, the better.

The time delay between when a command (action) is entered and executed. In general, the lower the latency, the better. There are three numbers in the latency description. An example of this is a DDR4 module with 16-17-17 latency has a CAS latency timing of 16, a tRCD timing of 17, and a tRP timing of 17. Although CAS latency ratings are the most common latency rating, it’s best measured in nanoseconds. This is called true latency.

Buffered, also known as registered, memory is designed for server applications and has a safeguard, or intermediary, between the module and data to lighten the electrical load and ensure data integrity by verifying that each piece of information sent to the memory is correct.

A module’s memory technology must match your system’s memory technology to be compatible. Memory is available in several generations of technology. For example, DDR, DDR2, DDR3, and DDR4. In addition, “upgrading your memory” usually refers to adding more GBs of RAM to the system. This does not mean adding DDR4 memory to a DDR3 system because the modules are physically different from one memory technology to the next and won’t fit in the memory slot. To verify compatibility in just a few clicks, use our Crucial® System Scanner or Crucial® Advisor™ tool.

This is also known as the memory rank, which indicates how the chips (the black components on the module) are engineered to process data. A higher numbered component configuration means the module is able to handle more data for more intense workloads, but some systems have a limit on how many ranks they’re compatible with.

This adds an extra level of data integrity that’s preferred for some server and workstation applications. Most desktop and laptop memory modules don’t need ECC.