Computer RAM Glossary

How to know the Capacity of a memory Module ?

Total number of available data memory cells on a module or RAM expressed in Gigabytes (GB) is the capacity of that Memory Module . For kits, listed capacity is the combined capacity of all modules in the kit. Higher capacity refers to the higher data stored on module.

What is CAS Latency ?

A standard, predetermined number of clock cycles for data read/writes to or from the memory modules and the memory controller. Once the data read/write command and the row/column addresses are loaded, CAS Latency represents the wait time until the data is ready. The lower the CAS Latency , the better the perormance of that module

What is DDR4 ?

DDR (Double Data Rate) Synchronous Dynamic Random Access Memory (SDRAM) It is fourth-generation memory technology, more commonly referred to as “DDR4 or PC4 .” DDR4 memory modules are not backward compatible with any previous generations of DDR SDRAM due to lower voltage (1.2V),Like the DDR4 will not be compatible to the DDR3 technology due to different pin configurations and incompatible memory chip technology.

What is DIMM Type , how to know it ?

UDIMM (non-ECC Unbuffered Dual In-Line Memory Module) is a long form-factor memory module with a data width of x64, most commonly used in desktop systems where error correction is not required and DIMM capacity is restricted. It refers to the desktop Memory Module

SODIMM (Small Outline Dual In-Line Memory Module) is a reduced form-factor memory module intended for smaller compute systems, such as laptops, micro servers, printers or routers. Refers to the laptop Memory Module.

Kit

A part number that includes multiple memory modules, typically in support of dual, triple, or quad channel memory architecture. For example, K2 = 2 DIMMs in the package to equal the total capacity. Like HX429S17IB2K2/16 refers to the kit of 2

How to check the Speed or Frequency

The data rate or effective clock speed that a memory module supports, measured in MHz (MegaHertz) or MT/s (Megatransfers per second). The higher the speed, the more data can be transferred per second. Like a 3200Mhz means that the data transfer rate is at a speed of 3200MT/second.

What is Latency Timing

The information below will help illustrate the various settings that can be adjusted when setting the memory timings in the motherboard BIOS for optimum performance. Please note that these settings may vary depending on motherboard make/model or BIOS firmware version.

Sample

15CL – 17tRCD – 17tRP/tRCP – 20tRA/tRD/tRAS

CAS Latency (CL): Delay between activation of a row and the reading of that row.

RAS to CAS or RAS to Column Delay (tRCD): Activates the row

Row Precharge Delay or RAS Precharge Delay (tRP/tRCP): Deactivates the row

Row Active Delay or RAS Active Delay or time to ready): Number of clock cycles between activation/deactivation of row.

Source: Google.