RAM Memory: DDR, DDR2, DDR3, DDR4

The information you need to be able to choose the right type and capacities of RAM memory for a desktop or laptop PC

A pair of DDR3 Corsair RAM DIMMS with heatspreaders in their slots on a motherboard

A pair of DDR3 Corsair RAM DIMM modules with heatspreaders in their slots on a motherboard

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This section of this website provides information on the different types of Random Access Memory – the RAM memory used in desktop and laptop PCs since 1997 when SDRAM was first made available to the present reign of DDR4 SDRAM memory. There were earlier types of memory, such as EDO RAM, but, as is the case with SDRAM, they are no longer being used. I only come across computers running DDR to DDR4 memory now.

The problems caused by faulty RAM memory

Since RAM memory is a crucial component, it must function 100% correctly all the time, otherwise it is responsible for a wide range of problems, some of the symptoms of which may appear to be caused by other components. The main problems are system crashes (sudden crashes, Blue Screens of Death (BSOD), etc) and freezes. Other symptoms are random restarts, file corruption that appears to be a software problem and the system issuing a BIOS beep code at startup.

If a relatively few memory addresses in the billions of such addresses go bad, which is usually the case, those bad addresses won’t cause problems until they are used – old old data is removed from addresses and new data is stored in them. RAM is an acronym that stands for Random Access Memory. The memory is used randomly by the system, so faulty addresses might not be used for a long time or might be used regularly, taking unused data out and put new data into them. Therefore, the fault can cause random system problems that are often unpredictable or irregular.

Memory diagnostic tools

1. – The Windows Memory Diagnostics Tool available in Windows 7 to Windows 10. Use this tool first. It works quickly, taking about half an hour to check 3GB of memory on a 32-bit version of Windows 7. The tool is under Administrative Tools in the Control Panel. It restarts the computer to run its tests and reports the result in the Notification Area when the system restarts. You need to be at the computer to read it because it comes up briefly and then disappears forever. The tool does not keep the report.

Bring up a link to it by entering the word memory in the Win7/10 Search box. If the computer cannot boot, use the Windows Repair media (disc for Win7 or flash drive for Win10) that can be created on any Windows 7/10 computer. The version in Win10 provides three levels of tests – Basic, Standard and Extended. The standard test is run by default, which detects most memory problems.

2. – Memtest86 is a free stand-alone, industry-standard tool that can be downloaded from https://www.memtest86.com/. It launches from a USB flash drive and provides a much more exhaustive set of diagnostic tests. It tests the memory independently of the operating system so it can be used on a computer running any version of Windows from Windows XP to Windows 10, or any other operating system.

Overclocking RAM

There are many articles and YouTube videos devoted to overclocking memory in order to improve performance for activities such as game-playing frame rates.. The video linked to below is a good one that illustrates how to use free software tools to obtain the settings to overclock DDR4 memory – for systems using AMD Ryzen processors – that are then entered into the system’s UEFI BIOS.

Setting XMP memory profiles

XMP Memory Profiles as Fast As Possible –

What You Should Know About XMP BEFORE you enable it –



Scroll down this single page or click the heading links to go directly to that information.

1. – Virtual memory and third-party memory managers
2. – RAM memory problems || How to install memory || How much memory do you need || SSDs & USB flash drives
4. – A fail-safe way to get the correct RAM memory
5. – Multi-channel memory architecture: Dual-channel DDR3 and quad-channel DDR4 memory
6. – Direct Memory Access – DMA
7. – RAM does not need a device driver
8. – Laptop SODIMM memory modules
9. – How much memory do the 32-bit and 64-bit versions of Windows Vista / 7 / 8.1 / 10 need
10. – RAM memory that is not recognized or only half or a quarter of it is recognised
11. – Low quality RAM and mixing brands can often cause problems
12. – Registered and ECC RAM memory
13. – UEFI/BIOS RAM memory settings taken from the BIOS section of motherboard’s user manual

POST: Strange RAM problem – memory not recognized by Windows 7 but identified in a Crucial scan

POST: Missing memory – Four good RAM modules, four good motherboard DIMM slots, only 8GB of 16GB shows in UEFI BIOS and Windows 10

POST: Under-used RAM: Windows 7 PC is only using 2.7GB of its 4GB RAM memory

POST: Memory limits – Why can my 64-bit Windows 10 PC only use 4GB of RAM memory?

POST: The causes of RAM memory problems and how to diagnose, troubleshoot and fix them

Virtual memory and third-party memory managers

Note well that regardless of whichever version of Windows a computer is running, its memory manager will manage the memory best. Windows also uses virtual memory – really disk space – when it runs out of real memory. You can set the virtual-memory swap file that Windows uses on the hard disk manually, but you should know what you are doing. An SSD should not make use of virtual memory at all – it should have been disabled automatically by Windows 7/8.1/10 when the computer runs from an SSD. It’s advisable to allow Windows to manage the real memory and the virtual memory. There are third-party memory managers that defragment the memory, but these are not necessary and can cause problems with the system that vary in their seriousness. They should not be used.

Memory management – https://en.wikipedia.org/wiki/Memory_management

The following video provides information on the virtual memory settings in Windows 10, but they are much the same in any version of Windows since Windows XP.

Windows 10 – Optimize Performance – Virtual Memory – Advanced System Settings – Speed Up Windows 10 –

RAM memory problems || How to install memory  || How much memory do you need || SSDs & USB flash drives

RAM is an acronym for Random Access Memory that is also known as volatile memory, because the data it holds is lost when the desktop PC or laptop/notebook computer using it is switched off. Briefly, RAM memory is used by the system to store data, drawn from the main data-storage hard-disk and SSD drive(s), in the form of files for processing by a computer’s central processing unit (CPU), also known as the processor.

RAM memory problems

The RAM Memory Problems section of this website deals with them.

How to install RAM memory

For installation instructions, visit the How to install DDR/DDR2/DDR3/DDR4 RAM memory that is part of the Build Your Own PC section of this website.

If you have the user manual that came with a motherboard you bought or which can be downloaded from its manufacturer’s website, it provides all of the information about that particular model, such as how to install RAM memory, drives, processor, connect the motherboard to the power supply unit, etc. Some motherboards provide onboard diagnostic LED lights that indicate if a component is not working.

Asus Sabertooth X99 motherboard's button that indicates if the RAM memory is compatible

Asus Sabertooth X99 motherboard’s button that indicates if the RAM memory is compatible. Click the image to view its full size

Some motherboards provide a button on the board that when pressed indicates if the memory is compatible. The diagram below is taken from the user manual of the Asus Sabertooth X99 motherboard, showing its MemOK! button. Press the button after installing the memory. The LED lights up to indicate if the memory is compatible or not.How much memory do you need

Computer memory requirements: How much memory do you need?


SSD and flash drives use flash memory<%2