One of the most common mistakes users make when purchasing a new computer or upgrading memory in their systems is to install the modules in the wrong memory slots. In this case, different situations can be encountered depending on the system or motherboard. The system may not boot, may not see the memory capacity correctly, or may not work with the full capacity of the memory modules. Users will rightfully think that there is a problem with the RAM modules.
In order to understand why this situation occurs, it would be correct to learn how the processor (CPU) accesses the memory (RAM).
In systems with DDR2 and later memory technologies, processors/CPUs support dual channel, triple channel, quad channel, and eight channel memory configurations in server systems. It is recommended that all channels be filled for best memory performance. If a RAM module is installed on only one channel in a dual-channel system or only two channels in a triple-channel system, the memory and system performance will be limited.
To give an example with the most general scenario:
A user with a two-module memory kit and a dual-channel motherboard should install the modules in one channel each. The order in which they should be installed and in which slots is specified by the motherboard or system manufacturer in the user manuals or on the diagrams on the system case.
Which slots should the RAM be installed in?
Current consumer motherboard models typically have four memory slots. They are configured to hold two memory modules per channel.
There are also models with 8 memory slots in motherboards for high-end gaming or workstation systems. Motherboards with DDR4 and DDR5 slots, which are the most commonly used memory technologies today, usually have 4 memory slots.
These memory slots are usually named A1, A2, B1 and B2, starting from the one closest to the processor. A1 and A2 indicate the 2 slots on channel A, B1 and B2 indicate the 2 slots on channel B. The images above show the memory slot names of MSI (DDR5) and Asus ( DDR4 ) motherboards.
Motherboard and system manufacturers recommend using both channels for best performance. This requires installing a memory module on each channel. Users should install the 2 RAM modules they have in slots A1 + B1 or A2 + B2, depending on the information provided by the system or motherboard manufacturer. Below are the installation diagrams for DDR4 and DDR5 motherboards offered by Asus and MSI according to the different RAM module counts.
For memory configurations recommended by the motherboard or system manufacturer, user manuals or product support pages on manufacturer websites should be reviewed. If new memory has not yet been purchased, users can easily find and purchase memory modules compatible with their systems with the Memory Search engine on our site.
If there is only one RAM module
Users can use their systems without any problems with a single module. However, for high performance with dual channels ; it is recommended to purchase another memory module with the same speed, capacity and latency values ​​and use it together. Of course, this is not a must.
There are two other RAM configurations for 4 memory slots:
The first is the configuration with 2 kits of different capacities. A user with 2 different kits of 2 x 4GB and 2 x 8GB modules should install the kits in separate channels for best performance. That is, it is recommended to use 8GB modules in slots A1 and B1, and 4GB modules in slots A2 and B2. For detailed memory configurations recommended by the motherboard or system manufacturer, please refer to the user manuals or product support pages on the manufacturer’s websites.
The second configuration option is to use 4 modules of the same speed and capacity. In this case, since all the memories have the same speed and capacity values, the order or which module is installed in which slot does not matter. Since all the slots and channels are full, the memories will operate in dual channels and provide the highest performance.
We also recommend you to watch the video below which shows how to install RAM in a desktop system.