Q. Why do I have to install my RAM modules in pairs?

Q. Why do I have to install my computer memory modules in pairs?

A. Normally a motherboard addresses memory through a 64 bit data channel. When a computer motherboard is designed to use Dual Channel memory access, it can address two identical RAM modules with two 64 bit channels of data flow (or one 128 bit channel in ganged mode). This improves the memory bandwidth (by a theoretical 2 x – however the effect on real world performance is more like 5% – 8% improvement with memory intensive applications). https://en.wikipedia.org/wiki/Multi-channel_memory_architecture#Dual-channel_architecture
So installing a dual channel pair gives a small but welcome speed improvement over the same amount of memory in single channel.

Q. What happens if I do not?

A. The vast majority of consumer computers will run in Single Channel access mode, so the computer will still run. Sometimes a single module must be installed in a specific slot to be recognized, consult the user manual. A few higher end machines and servers will not run without pairs or other particular configurations of memory – check your owners manual.

Q. If the total RAM is recognized why does it matter if they are in pair or not?

A. Even if the memory is not a matched pair, most machines will recognize the full amount of RAM and run. You would just be giving up the potential speed benefit of Dual Channel memory access

Q. Do I have to buy special Dual Channel RAM modules?

A. There is no difference to the memory module, whether it is used as a single, or as a member of a dual channel pair. They are the same modules, manufacturers simply sell kits of 2 as a convenience to know you are getting a matched pair.

Q. So then, could I take any two random modules and put them in to work in Dual Channel access?

A. It’s a little more involved than that. Whether two modules can be paired as a Dual Channel set depends on the memory controller of the machine (which these days is embedded on the CPU). A few motherboards can address dissimilar modules in Dual Channel, and some motherboards are extremely restrictive in what they will recognize.

The official answer is that the two modules must match for Speed, Size and Composition. The first two are easy to determine, but Composition means how the module is made, the number and density of memory chips on it, and how those memory chips are organized in rows and columns of addresses. You don’t have an easy way to know the internal organization of the module. Although two modules from different manufacturers may match sufficiently to be a Dual Channel set in your motherboard, the easiest way to know is to install two matching model numbers from the same manufacturer as a kit.

Q. Is there higher than dual channel access?

A. Some machines implement triple- or quad-channel access. Six- and eight- channel access is usually seen only in higher end servers and workstations with two or more processors. On those machines, pay particular attention to the memory population rules in your owners manual.

Check with Canadaram for advice on the correct memory configurations for your particular machine

Q&A is a compilation of answers we have given to questions around the web

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