Browse our FAQs about RAM

General Knowledge

Can I mix different DRAM memory speeds?

You can use memory modules of different speeds as long as they are faster than those specified for your computer. It is recommended to use modules of the same speed as those already installed in your system. If you do mix speeds, the modules will all run at the speed of your slowest modules.

Can I mix DDR, DDR2 and DDR3 modules in my PC?

No. DDR3, DDR4 and DDR5 are different. You must select the correct type to match your system. DDR3, DDR4 and DDR4, DIMM and SODIMM modules have notches in different places to prevent insertion into a incompatible system

What are memory module RANKS and how are they used ?

A RANK is a 64bit (or in a case of an ECC module 72bit) data width addressable area of a memory module. Currently a module can be: SINGLE RANKED (Rank 1) DOUBLE RANKED (Rank 2)QUAD RANKED (Rank 4).OCTO RANKED (Rank 8)1 RANK = 64bit width (or 72bit with ECC). Ranks are for interleaving to make a system run faster. This is where one device or part of a device is being accessed for data whilst another device or part of a device is getting ready to deliver data.

Can I install an ECC DIMM on a Non-ECC motherboard?

Most motherboards that do not have an ECC function within the BIOS are still able to use a module with ECC, but the ECC functionality will not work.

Keep in mind, there are some cases where the motherboard will not accept an ECC module, depending on the BIOS version.

What are “unbuffered” and “registered” (reg) memory modules ?

UNBUFFERED – No buffer the memory is connected directly to the chipset controller. Memory modules that are used in desktops or notebooks are mostly unbuffered.

BUFFERED – A buffer is used to help the system control large amount of memory.

REGISTERED – Registered modules do not have a buffer but do contain a register that delays all information transferred to the module by one clock cycle, this increases reliability and the main application is for servers.

What is the difference between CL2 and CL3?

CL stands for CAS (Column Access Strobe) Latency, which is a term referring to the time that it takes to retrieve data from the module.

  • CL2 and CL3 refer to the amount of clock cycles that it takes before the initial stream of data is sent.
  • CL2 modules wait two clock cycles before sending data.
  • CL3 modules wait three clock cycles before sending data.
  • CL2 modules are faster since they only wait two clock cycles. Some systems may specify either CL2 or CL3 memory.
How do I know which is the first memory module socket?

Normally the memory module sockets (slots) are marked 0, 1, 2, 3 etc… with socket zero being the lowest. If there are no markings on the motherboard, the socket nearest to the CPU is normally considered socket zero (or the first socket).

Will additional memory speed up my computer?

In general yes it will speed up your computer.

Additional memory will not increase the speed of the CPU, however it will reduce the time a CPU spends waiting for information from the hard drive. RAM provides data to a CPU faster than a hard drive, so it will not take as long for programs to execute. If your system is running slow and you have less than the ideal amount of memory, -increasing the memory is an easy way of boosting system performance.

What is ESD?

ESD (Electrostatic Discharge) is static electricity. ESD occurs when touching an object that conducts static electricity. ESD can damage memory modules.

To protect your memory module from ESD, always store components in antistatic packaging until use. Before handling memory modules we recommend you discharge any static by touching an earthed metal object such as a nearby unpainted radiator or pipe.

ESD wrist straps can be purchased to provide additional ESD protection.

What is the difference between Physical and Virtual Memory?

Physical and Virtual memory are two different things. Virtual memory allows you to use some of your hard drive as though it were RAM. Your hard drive is up to 100 times slower than RAM. When you upgrade your RAM, you can reduce or eliminate the use of virtual memory. Upgrading RAM makes more (physical) memory available to complete tasks previously handled by virtual memory.

What is ECC (Error Correcting Code)?


This uses technology on the motherboard to test the accuracy of outgoing and incoming data by using a checksum. Some errors are automatically corrected; ECC modules are normally used in high end workstations and servers where data integrity is vital. ECC applies to DDR3, DDR4 and DDR4 modules.

ECC modules have a extra memory chip for every eight chips. e.g. 9 or 18 as opposed to 8 or 16 for a NON-ECC module.

In most cases you can install a ECC module into a NON-ECC system but generally a ECC system will require a ECC module. Please check your PC manual.

What is Parity?

Parity is a method of checking for data corruption in memory. One check-bit is added to each byte (8 bits). Errors are detected, but not corrected.

Can I visually see if the modules have ECC?

In general yes, count the total number of memory chips on the module. If the number of data chips can be divided by 3 then the module has ECC. (i.e. ECC will have an odd number of data chips)

What is the difference between a SIMM and a DIMM?

A SIMM (Single In-Line Memory Module) has a single line of connectors. Connectors on each side of the Board are the same. SIMMs are now obsolete.

A DIMM (Dual In-Line Memory Module) has 2 lines of connectors. Connectors on each side of the board are not connected. DIMMs and SoDIMMs are supported in DDR3, DDR4 and DDR5

What is JEDEC?

Jedec is the Joint-Electron-Device-Engineering-Council, an important body that sets the standards in the memory industry.

Areas like the dimensions and functionality of DIMMS are set by JEDEC. This ensures compatibility.

What is Dual-Channel Memory?

The phrase Dual-Channel memory is incorrect. The true statement is Memory in Dual-Channel mode. This refers to a machine utilising a pair of modules processing the data more efficiently and reducing system latencies (interleaving). If your machine is Dual-Channel mode compatible then you will see the benefit when using compatible memory in pairs.

What is SDRAM?

SDRAM (Synchronous Dynamic Random Access Memory) is the term used for all memory that run with timing cycles that are synchronous to the Motherboard. Prior to SDRAM, memory ran in its own clock cycle which caused waiting time for the CPU.

SDRAM was introduced at the same time as the 133Mhz Pentium Processor.

What is the difference between SDRAM and DDR?

Single Data Rate (SDR) SDRAM has been superseded by faster Double Data Rate (DDR RAM)
DDR RAM with a Double Data Rate is achieved this by “double pumping” (transferring data on both the rising and falling edges of the clock signal), hence double the data rate. The other differences include : number of pins, voltage, speed and latency.

SDRAM will not fit or work in a DDR system and vice-versa.

What is an SPD?

The SPD (Serial Presence Detect) chip on a memory module is an additional chip holding 128Hex bytes of information about the module.

This identifies the module to the BIOS during POST so the Motherboard knows its characteristics and timings that can be used. This was introduced at the same time as SDRAM.

What is POST?

POST (Power On Self Test) occurs as the computer is turned on. The BIOS checks each necessary component is responding and reads info for access timings. In the case of memory modules, it will read the SPD (Serial Presence Detect) to check compatibility and access timings. If the wrong type of memory is installed or if the memory has become faulty – there may be a POST error reported, sometimes with beeps.

Why does my computer need memory modules installed in pairs?

The most common reason is that the machine is designed to work in Dual Channel Mode where the memory controller utilises a pair of modules in turn (interleaving) so that it can reduce the time that it waits whilst the memory is read giving a better performance.

What is a NanoSecond?

A nanosecond (ns) is one billionth of a second (10-9 s).

They are used to show the length of time a memory chip takes to complete a single read/write cycle.

What is CAS Latency ?

CAS Latency (CL) stands for Column Address Strobe. This is the number of clock cycles that pass from when an instruction is given for a particular column and the moment the data is available.


How can I tell how much memory is installed in my printer?

Normally the amount of installed memory will show when you print a status page. Please refer to your device’s handbook for instructions on how to do this.

Cisco UCS Manager is showing that servers with Integral memory modules have “Invalid FRU” DIMMs installed. What does this mean?

The Cisco UCS Manager uses a catalogue system to identify DIMMs. In some situations, for example where the UCS Catalogue in service is not the most recent, or if the Integral components are not recognised, then these messages will be reported for servers with Integral memory installed.

However, there is absolutely no impact on the memory performance and these messages can be safely ignored.

If the FAQs cannot answer your support question, please complete and submit the support form below and a member of our Technical Support team will be in touch. We take pride in our highly rated customer service.