We aim to make everything on the Mr Memory website easy to understand, but if there is a term or abbreviation that needs explaining, you should find it here.

32-bit / 64-bit Windows

Refers to the way a Computer's processor (CPU) handles information. The 64-bit version of Windows handles large amounts of RAM more effectively than a 32-bit system.


Also known as a 'Base system', this is a partially assembled/unassembled kit of computer parts that allows more customisation than an OEM computer system. Available in most form factors and you will usually need to add RAM, storage, graphics card and external peripherals.


A number system that only uses 2 digits - 1 and 0. Computers read and convert these numbers, so all the data on your computer is stored and processed as 1s and 0s.


The 'BIOS' or 'Basic Input/Output System' is firmware used to initialise and start up a computer and provides services for the operating system and programs. The Computer’s CPU will access the BIOS before the Operating System is loaded, checking that the hardware connections are all OK.

The BIOS lives in a ROM (read-only memory) chip on the Computer's motherboard and can sometimes be updated to support new hardware including CPU's and faster memory speeds. Most people will never need to access the BIOS of their Computer, but it can be done by holding a key when the Computer is starting up. Check your manual for more on this.

Booting / Bootup

Starting up a computer. A cold or hard boot is when the power had been turned off. A warm or soft boot is restarting the computer without turning off the power.


Software that is used to browse the internet (e.g.Google Chrome, Firefox, Internet Explorer, Edge).


A unit of 8 bits that represent a single character in the Computer Memory (e.g. the word 'CAT' has 3 characters, so would be represented by 3 bytes).


The Cache (pronounced 'Cash') is an area where information that is often in use can be temporarily stored and retrieved quickly. (e.g. your Web Browser will use a cache to store URLs of recently visited Websites on your hard drive, so they don’t have to be downloaded again and again. Accessing the hard drive is much quicker than accessing the Internet).

Chip / Microchip

Tiny sliver of silicon that contains miniature electronic circuits that stores millions of bits of information.


A group of integrated circuits that are used together to serve a single function. Examples include - Intel Z170, H170, H110 and B150.

Clock Speed

The speed that a Computer processes information. Usually measured in Megahertz or Gigahertz. A 1.8GHz Processor has twice the clock speed of a 900MHz Processor.


'CompactFlash' or 'CF' Cards are a type of flash memory card used mainly for storage in high end DSLR cameras.

Due to their robust design and low power consumption they are also commonly used for industrial purposes.


This is a small text file that is stored on the Hard Drive, which relays back to a web server things about the user, their computer and computer activities. It allows a server to deliver a page tailored to the user. Also a very tasty variety of biscuit.


The CPU ('Central Processing Unit' or 'Processor') is the main microprocessor in a Computer and performs operations requested by the operating system and programs.


'DDR' (Double Data Rate), also known as DDR1, is the first generation of SDRAM, introduced to read and write 2 words of data per clock cycle. Typical DDR types are 266, 333 and 400MHz.

DDR DIMMs have 184 pins in total (92 on each side) and a single notch. DDR SODIMMs have 200 pins in total and a single notch near one side. The usual voltage is 2.5V.


'DDR2' (Double Data Rate), was introduced in 2003 as a replacement for DDR(1). DDR2 doubles the minimum read and write of data to 4 words per clock cycle.

DDR2 uses less power as it runs the internal clock at half the speed of the data bus. The best DDR2 modules are twice as fast as the best DDR(1) modules. Typical DDR2 types are 533, 667 and 800MHz.

DDR2 DIMMs have 240 pins in total and a single notch. DDR2 SODIMMs have 200 pins in total and a single notch nearer to one side. You can use higher speed DDR2 modules with lower speed modules - the motherboard controller will be bound to the limits of the lower speed modules. We would always recommend using matched modules though, to give the best performance using Dual Channel mode.


'DDR3' (Double Data Rate), was introduced in 2007 as a replacement for DDR2. DDR3 can transfer data at twice the rate of DDR2 and uses less power (1.5v or 1.35v).

Common speeds of DDR3 are 1066, 1333 and 1600MHz. Faster speeds than this are usually found in machines used for gaming where speed is critical.

DDR3 DIMMs have 240 pins in total and a single notch. DDR3 SODIMMs have 204 pins in total and a single notch, closer to the centre than on 200 pin SODIMMs.

DDR3 also works in Dual Channel mode (kit of 2) and mainly benefit from Triple Channel mode (kit of 3).


'DDR4' (Double Data Rate), was introduced in 2014 as a successor to DDR3. DDR4 modules have faster clock frequencies and data rates than DDR3 modules and consume less power (1.2v compared to 1.5v for DDR3).

DDR4 DIMMs have 288 pins, which are slightly closer together than pins on older boards. DDR4 SODIMMs have 260 pins, which are also spaced closer together.


'DDR5' (Double Data Rate), was introduced in 2020 as a successor to DDR4. DDR5 modules have faster clock frequencies and data rates than DDR4 modules and consume less power (1.1v compared to 1.2v for DDR4).

DDR5 DIMMs have 288 pins just like the DDR4 predecessor. DDR5 SODIMMs have 260 pins, which is also the same as the DDR4 SODIMM predecessor.


'DIMM' (Dual In-line Memory Module) refers to the type of memory module commonly used in desktops and servers.

A DIMM is a series of DRAM integrated circuits. The modules are mounted onto a PCB (Printed Circuit Board). DIMMs are replacements to SIMMs (Single In-line Memory Module), as the most popular type of module. They have separate electrical contacts on each side of the module and a 64-bit data path.


'DRAM' stands for Dynamic Random Access Memory. This is the memory used in Desktops, Laptops, Servers and some other devices.

A computer stores quickly accessible data in the form of 0s and 1s. It is dynamic because it refreshes its capacitor charge periodically with new electricity, compared to the older SRAM (Static Random Access Memory).

Data is stored in the capacitors within an integrated circuit (also known as a Chip). DRAM memory is a volatile memory which means it loses its data very quickly once the power is removed.

Dual Channel

'Dual-Channel' is a technology which doubles the data throughput from the memory to the CPU.

For Dual-Channel mode to function, memory modules must be installed in matched pairs e.g 2 x 512MB or 2 x 1GB etc. If memory is installed in unmatched pairs e.g 512MB plus 1GB - then Dual-Channel mode is simply disabled, however the computer will still function correctly if the memory is not matched.

Dual-Channel is simply an additional function, however this is not available on all computers. If your computer accepts and utilises Dual Channel memory we ALWAYS recommend you use this as in doing so you will gain around 15% to 20% in performance of the memory.


A CPU with 2 processor cores in the same integrated circuit. Each processor has its own cache and controller, enabling it to function efficiently as a single processor. Examples include the Intel Core Duo and AMD X2.


'ECC' (Error Correction Code) is a technology used on certain kinds of RAM modules that detects data errors and corrects them. Errors occur due to electrical or magnetic interference inside the machine. This interference can corrupt the data being processed.

ECC memory is mostly used in Servers and Workstations. This is because the ECC function is able to detect and correct these errors with no input from a user - therefore increasing data reliability. This is vital because if an error occurred and was not corrected, the server would crash, causing problems for those reliant on the server and the information that it stores.

ECC modules are manufactured in different ways to allow for different functions. The most common types are: Unbuffered, Registered and Fully Buffered.


EEPROM (Electrically Erasable Programmable Read-Only Memory) is a type of memory that can be erased by exposing it to an electrical charge. EEPROM retains data even when the power is turned off, but is not as fast as RAM. An EEPROM chip is similar to Flash memory, except the data is written/erased 1 byte at a time, whereas Flash allows data to be written/read in blocks (making flash memory faster).


'Electrostatic Discharge' or 'ESD' is a tiny version of lightning. It is the release of static electricity when two objects come into contact. This can be damaging for Computer Hardware.

To prevent ESD you could use a special anti-static wrist strap or earthing mat. If you do not have access to these things, simple things like touching a radiator or baking tray can actually ground you.

Top Tips:

  • Remove all cables from the back of the computer (power, keyboard etc).
  • Avoid clothing that causes static, such as a wooly jumper.
  • Sitting on a chair can generate static, so best to stand if possible, whilst upgrading.

Flash Memory

'Flash Memory' is non-volatile storage. This means that it retains data even if it is non-powered and it can be electrically erased and reprogrammed. In comparison, RAM is volatile, which means it loses anything it contains when the power is lost.

Invented by Dr. Fujio Masuko of Toshiba in the 1980s. It was called “Flash” because the process of erasing the data reminded Dr Masuko’s colleague of the flash of a camera.

Flash memory is widely used for Camera, Phone and Tablet Storage.

Form Factor

The physical size and shape of a device. Memory form factors include SODIMM (smaller for Laptops and All-in-Ones) and DIMM (larger for Desktops).

Fully Buffered

'Fully Buffered' Memory (FB DIMM) takes some of the functions of the memory controller and puts it on the memory module. It has an advanced memory buffer, enabling an increase to the width of the module but keeping the pin count of the memory controller at a reasonable level.

These are only available for DDR2 memory, however the notch on the FB DIMM is in a different location compared to a standard DDR2 DIMM, preventing incorrect installation.


1GB or 1 Gigabyte is the equivalent of 1,073,741,824 Bytes OR 1,048,576 Kilobytes OR 1,024 Megabytes.

Hard Drives and SSDs are normally measured in Gigabytes or Terabytes. 'Giga' comes from the greek 'gigas', which means giant.


A 'Hard Disk Drive' or HDD is a magnetic storage device for permanent data for computers. Modern drives often contain several GBs or TBs of data. Most computers will have 1 or more internal hard drives, but you can also add an external hard drive to a computer for expansion, backing-up or making your data mobile.

SSDs have become a popular alternative to HDDs in recent years - as they provide many advantages over HDDs including significantly faster performance, improved reliability and lower power consumption.


A Heatsink is made to reduce and spread heat emitted from certain computer components including CPU and RAM chips. The majority of memory modules do not need a Heatsink, as they do not usually generate enough heat, however some Apple or Overclocked machines will benefit from Heatsinks.

If your Computer requires Memory modules with Heatsinks you will find them listed against your Computer on the Mr Memory website.

Hot Swappable

'Hot' means 'active' or 'powered on'. A hot swappable device is a component that can be removed/added whilst the computer is running. Common examples are Server hard drives and USB devices. RAM is generally NOT hot-swappable.


'Integrated Drive Electronics' or 'IDE' was a widely used internal drive interface for connecting mass storage devices such as hard drives and optical drives. Also known as 'ATA', in 2003 IDE was superseded by the now common place 'SATA' interface.


'JEDEC' (The Joint Electron Device Engineering Council) is an independent organisation, which develops standards for the microelectronics industry.

JEDEC committees developed the standards for specifications of DRAM memory and flash components. All memory supplied by Mr Memory is JEDEC compliant and our Memory Experts are fully familiar with all their standards requirements.


'Latency' is the delay between transmitting data between the CPU (Central Processing Unit) and SDRAM. It is measured in memory bus clock cycles.

SDRAM access has 4 main clock cycles (t stands for time):

  • tCAS - the number of clock cycles required to read a column of data on the SDRAM module (Column Access Strobe)
  • tRCD - the delay between the Row Address Strobe (RAS) and the CAS. Represents the delay between CPU defining the row and column of the memory block and the actual read or write to that row and column
  • tRP - Row Pre-charge time. The number of clock cycles needed to terminate access on a given row, and to open access on the next row
  • tRAS - Active to Pre-charge delay (Row Active Time). The number of clock cycles between the data request and pre-charge command of a given row inside a memory block

The JEDEC Standard defines that each row must be refreshed every 64ms or less. Refresh logic is provided in the DRAM Controller, which ensures that the Data Bus is never required for a read and a write at the same time.


'LRDIMM' (Load Reduced Dual Inline Memory Module) are a type of DIMM that replace the register on an ECC Registered Module with an Isolation Memory Buffer component. They also deliver higher speeds at higher capacities.

Many modern DDR3 and DDR4 servers will take LRDIMM modules, but please check your model specs for more information.

Matched Pair or Kit

A 'Matched Pair' or 'Matched Kit' of memory modules is a kit of 2 or more identical modules, guaranteed to work together in the same system and at the same speed.

Maximum Memory

The 'Maximum Memory' refers to the maximum amount of Memory (RAM) that your computer can physically support. This is divided by the number of 'Memory Slots' in the computer.

For example, if you have 2 slots and a maximum memory of 8GB, you would need to install 2 x 4GB modules to reach the maximum. If you wish to install the maximum memory, please note that you may need to remove and replace some or all of the existing modules.

The maximum amount of memory supported by your operating system may be lower than the computers 'Maximum Memory' (e.g 32-bit versions of MS Windows). Please see the support section for details of Windows memory limitations.


The 'megabyte' or 'MB' is a measure of memory/storage capacity. There are 1,024 megabytes in a Gigabyte.

Memory Slot

A 'Memory Slot' is soldered to your computer or laptop motherboard and is where the computer memory (RAM) is connected.

Most computers have at least 2 slots and often will have spare slots for upgrading. However, depending on the size of the installed modules you may need to replace all or some of the existing modules in order to increase the overall amount of RAM.

Each generation of RAM (e.g. DDR2, DDR3 etc) has a unique slot design to prevent installation of the wrong type of memory.

We know exactly which type of slot your computer has, so when you find your computer model on the Mr Memory website you can be assured that the memory upgrades offered will be fully compatible.


A Computer’s Microprocessor speed is measured in 'Megahertz' or 'MHz'. 1MHz represents 1 million clock cycles per second.

Micro SD / Micro SDHC / Micro SDXC

A 'Micro SD Card' is a smaller version of the SD Card (Secure Digital), also utilising flash memory.

Commonly used in mobile devices such as Smart Phones, Cameras, Sat Navs and Tablets, the first generation was available in sizes up to 2GB.

Micro SDHC (Secure Digital High Capacity) is the next generation of Micro SD Card providing higher read and write speeds and capacities up to 32GB.

Micro SDXC (Secure Digital Extended Capacity) is the latest generation of Micro SD Card, providing further speed improvements and capacities above 64GB.

Older generations of Micro SD Card can be used in newer devices, however you will not be able to use a newer generation in an older device. Please check your manual for compatibility or find your device on the Mr Memory website.


A 'Module' aka. 'Board' or 'Stick' refers to a printed circuit board where DRAM integrated circuits are mounted.


A 'Motherboard' aka 'Mainboard', 'Base Board', 'System Board' or 'Logic Board' is a printed circuit board which allocates power and allows communication to vital Computer Hardware components - such as the Memory and CPU. It also provides connectors for other peripherals.


'Network attached storage' or 'NAS' is a storage device connected to a network that allows storage and data retrieval from a centralised location. These devices typically do not have a keyboard or display and are configured through a browser-based program.


A cut-out section along the bottom of a memory module is know as a 'Notch'. By matching the notch to the notch in the memory slot on the computer, you can be sure you have installed memory with the correct form factor and in the correct orientation as each DDR type has a different notch position.


'Non-volatile Random Access Memory' or 'NVRAM' is a type of RAM that retains data after the Computer’s power is turned off. NVRAM is faster than Volatile Memory for reading/writing. Example - the EEPROM is NVRAM, used for the BIOS in many computers.


The 'petabyte' or 'PB' is a measure of memory/storage capacity. 1PB is equivalent to 1,048,576GB or 1,024TB.


A memory module is a narrow 'Printed Circuit Board' or 'PCB' that contains RAM chips - normally green in colour. This board is made up of several layers that contain traces and circuitry to control the movement of data.


'Peripheral Component Interconnect Express' aka 'PCI Express' or 'PCIe' is a high-speed serial computer expansion bus standard used commonly for connecting peripherals to a computer motherboard such as graphics cards, WLAN cards, and SSDs. Performance is measured in data throughput speeds such as x8 and x16.


An external device that provides input and output for the Computer is known as a 'Peripheral'. Examples include your mouse and keyboard (input) and printers and monitors (output).

Plug and Play

A 'Plug and Play' or 'PnP' device works with a computer system as soon as it is connected. No user intervention or physical device configuration is required, the Computer just simply recognises the device.


A CPU with 4 processor cores in the same integrated circuit. Each processor has its own cache and controller, enabling it to function efficiently as a single processor. Examples include the Intel Core i7 and AMD Phenom X4


A 'Redundant Array of Independent Disks' or 'RAID' is a method of spreading information across several disks that have been set up to work as a unit. By placing data on multiple disks, input/output (I/O) operations can overlap in a balanced way - improving performance. There are several different RAID configurations that can provide a mix of improved performance and redundancy by mirroring data to multiple drives.


'RAM' is an abbreviation for Random Access Memory. A computer uses RAM to hold temporary instructions and data needed to complete tasks. This enables the computer's CPU (Central Processing Unit) to access instructions and data stored in memory very quickly.

Ranks and Banks

A 'Rank' is a 64-bit (72-bit on ECC) area of data that is created using all or some of the memory chips on the module.

A 'Bank' is a sub-unit of a single memory chip.

Memory modules are available as either Single Rank (1R), Dual Rank (2R) or Quad Rank (4R). It is not necessarily the amount of chips on a module that determines its rank, it can depend on how the chips are engineered. A module with chips on both sides could still be any of the above ranks.

The number of Ranks is often combined with the number of Banks to indicate the geometry of the module (for example a module labelled as 2Rx8 is dual rank with 8 banks per chip).

Some machines, especially servers and workstations will only work with a specific rank/bank combination. At Mr Memory we have a great understanding of the different rankings used in server configurations, so we will always supply the correct modules for your machine.


'Registered' is a type of ECC memory with buffers for a better flow of data. This increases data reliability when compared to Unbuffered memory. They place less electrical load on the memory controller, allowing systems to be stable with more memory modules in.

Registered modules have 2 extra chips, compared to a standard non-ECC module. Modern Servers are equipped to deal with either DDR3 Unbuffered or Registered memory. However, they cannot accept mixed, it must be one or the other.

Retina Display

The term 'Retina Display' was introduced by Apple to describe a display with a resolution of over 300 PPI (pixels per inch). At a normal viewing distance it is not possible to identify the individual pixels on a Retina Display.


'Read Only Memory' or 'ROM' is a type of memory chip that retains pre-recorded data even when there is no power (unlike RAM). Commonly used for storing 'Firmware', in most cases it is not possible to change the data stored on a ROM chip.


'Serial Advanced Technology Attachment' aka 'Serial ATA' or 'SATA' is an interface used to connect ATA drives to a Computer’s motherboard.


'Small Computer System Interface' or 'SCSI' (pronounced "Scuzzy") is a Computer interface, used for high-speed hard drives. SCSI supports faster data transfer than IDE and is more commonly used in high-end servers.


'SD Cards' were the first generation of Secure Digital Memory Card. Utilising flash memory up to 2GB in size, SD Cards are used in many digital devices such as cameras and tablets.

SDHC (Secure Digital High Capacity) is the next generation of SD Card providing higher read and write speeds and capacities up to 32GB.

SDXC (Secure Digital Extended Capacity) is the latest generation of SD Card, providing further speed improvements and capacities above 64GB.

Older generations of SD Card can be used in newer devices, however you will not be able to use a newer generation of SD Card in an older device. Please check your manual for compatibility or find your device on the Mr Memory website.


'SDRAM' (Synchronous Dynamic Random Access Memory) is memory that is synchronised with the System Bus (which connects all the major components of a computer system). Unlike DRAM, SDRAM waits for a clock signal before responding to control inputs.


A 'Server' is a computer that provides data and computing resources to other computers on the same network. They are often dedicated, meaning that they perform no other tasks beside their server tasks.


'SODIMM' (Small Outline Dual-Inline Memory Module) refers to the type of memory module commonly used in laptops, notebooks, printers, iMacs and other all-in-one machines.

A SODIMM is a series of DRAM integrated circuits. They are smaller in design to DIMMs and have 4 or 8 chips on each side of the board.


'Serial Presence Detect' or 'SPD' is information stored in a read-only memory chip (EEPROM) on an SDRAM memory module. This tells the BIOS the module’s size, speed, data width and voltage. Without SPD, the computer is unlikely to boot, or may boot with issues.


'SSDs' (Solid State Drives) are a modern replacement to Hard Disk Drives. SSDs have many benefits over traditional Hard Drives including speed, weight and energy savings.

SSDs are up to 20 times faster than traditional Hard Drives. They also consume far less power and are virtually silent.

Installation is fairly straightforward and our Memory Experts can provide full detailed advice and support if and when needed. SSDs supplied by Mr Memory also come with installation kits and instructions. Installation of SSDs for Apple Computers is more tricky but Mr Memory Experts are fully trained and on hand to assist in any cases of confusion.


The 'terabyte' or 'TB' is a measure of memory/storage capacity. 1TB is equivalent to 1,0246GB or 1,048,576MB.

Thin Client

A 'Thin Client' or 'Network Computer' is a small desktop PC that often uses flash memory instead of a hard drive to store the operating system. Applications and data are stored and accessed directly from a server.

Triple Channel

'Triple-Channel' is a technology which increases the data throughput from the memory to the CPU.

For Triple-Channel mode to function, you must install matched memory modules in multiples of 3 (e.g 3 x 1GB or 6 x 2GB). If memory is installed in unmatched pairs e.g 1GB plus 2GB - then Triple-Channel mode is simply disabled, however the computer will still function correctly if the memory is not matched.

Triple-Channel is simply an additional function, however this is not available on all computers. If your computer accepts and utilises Triple Channel memory we ALWAYS recommend you use this to get the best performance from the memory.

Unbuffered (UDIMM)

'Unbuffered' is a type of ECC memory that does not include any buffers. It is the most commonly used type of ECC memory and has a lower maximum capacity than Registered.

The standard memory used for Laptops and Desktops is also called Unbuffered memory, but it is the Non-ECC type. ECC Unbuffered modules will have nine chips on one or both sides of the module as opposed to 8 on a standard Non-ECC module. The ninth chip is the ECC chip.

USB Flash Drive

'USB Flash Drives' are now the most popular media for storing and transporting personal files such as photos, videos, music and documents. Utilising flash memory USB drives are available in a wide range of styles and capacities. There are currently 3 generations of USB drive, USB 2.0 and USB 3.0 provide huge speed improvements over the previous generation.

USB Flash Drives are also a great way to backup your important files.

Virtual Memory

'Virtual Memory' is a feature of the operating system that lets a computer borrow some space on the hard drive when all of the RAM is in use.

The read/write speed of a hard drive is much slower than RAM, so if your system is relying heavily on virtual memory, it will drop in performance. To solve this, make sure you have enough RAM to handle all your work.

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Americanino Limited T/A Mr Memory
D3 Yeoman Gate, Yeoman Way
Worthing, West Sussex
BN13 3QZ

Registered in England & Wales - Company Registration No: 02012072.
UK VAT No: GB 641 1660 65.

The trademark Mr Memory is the exclusive property of Americanino Limited and is protected by UK Trademark Registration No: 2616298.

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