Which RAM Slot to Use? – Does it Matter?

Yes, it does matter what RAM slot you use. When building a new PC, there is a ton of do’s and don’ts that you need to be aware of. One such big caveat is when installing RAM sticks on your motherboard. So which RAM slot to use first?

Well, essentially, it all depends upon what motherboard you have and how many RAM sticks you have. If you have a single RAM stick, then it wouldn’t matter which one you use first. However, with two or more sticks, the slots do start to matter due to Dual Channel technology.

I explain below in detail which slots to use. But, TL:DR; a general rule is that, if you have a motherboard with four RAM slots, use 2nd slot , then 4th slot if you have another stick, then 1st and then 3rd. 

But in reality, motherboard’s manual is your best friend here to determine the exact slots that would enable dual channel. For Dual Channel technology to work, the RAM sticks have to be plugged into the right slots.

If you have two RAM slots, it doesn’t matter which slot you use for your RAM, but if you have four or more, then it does matter.

Dual Channel is essentially a technique that makes accessing the RAM modules by the CPU faster.

In the following text, I explain in detail which RAM slot to use and would it matter which RAM slot you use for your modules. 

What is Dual Channel RAM Technology?

Dual-Channel basically falls under the larger umbrella term of Multi-Channel memory technology.

Dual Channel, as the name suggests, is the technology through which the CPU can access memory through two independent 64-bit buses – or information highways in simple terms.

Dual Channel memory, as such, allows for a faster transfer of data between the CPU as compared to a Single Channel memory.

There are also triple and quad channel RAM technologies. However, as far as the commercial PCs are concerned, almost all of them support dual channel memory only.

In order for Dual Channel technology to work, you need to

  1. Have TWO DDR, DDR2, DDR3, DDR4, or DDR5 RAM sticks.
  2. Have a CPU that Supports Dual Channel technology
  3. Have a Motherboard that supports Dual Channel technology

Single vs Dual Channel Memory Performance Comparison

As far as the performance goes, Dual Channel RAM does NOT give you double the performance benefit as compared to a single channel RAM.

However, GamersNexus.net had a done a comprehensive study on this. The graph below shows the single and dual channel RAM performance testing on MaxxMem, which is a benchmark that tests the memory bandwidth, memory write, read and copy speeds.

Single and Dual Channel Memory
Single and Dual Channel Memory Performance Benchmark. Source: GamersNexus.net

I recommend watching the entire video where GamersNexus.net benchmarks Single vs Dual Channel RAM. 

But from the MaxxMem results, there is almost a 30% improvement in the performance when using Dual Channel memory when compared to Single Channel, so it would a shame to not utilize the Dual Channel memory if both your motherboard and the CPU support it.

Of course, the performance difference varies depending upon the application and the task you run and it won’t always be an optimistic 30% improvement, but the important point is that leveraging Dual Channel WOULD NOT HAVE TO COST YOU AN EXTRA PENNY.

All you need to do is have two RAM sticks plugged into the right slots!

Also Read: How to Check if RAM is Dual Chanel?

So Does It Matter Which RAM Slot To Use?

Yes it does matter.

For Dual Channel technology to work, you have to plug the RAM modules in the right slots.

There are two ways to figure out which slots to use for your RAM.

1. Use the Motherboard Manual to Determine Which RAM Slots To Use First

This is by far the most definitive way to find out which RAM slots to use for your modules.

the following image shows an excerpt from the ASUS ROG Crosshair VII Hero motherboard’s manual.

ROG Crosshair VII Hero
Memory Configuration for ROG Crosshair VII Hero. Source: ASUS

You can see here that this motherboard recommends the following:

  • If you have one RAM stick – use DIMM_A2 slot (4th slot)
  • If you have two RAM sticks – use DIMM_A2 and DIMM_B2 (2nd and 4th slots) – THIS WOULD ENABLE DUAL CHANNEL
  • If you have four RAM sticks – Occupy the rest of slots. – This would enable TWO SETS of dual channel.

2. Using RAM Slot Color Codes (Older Motherboards)

Some motherboards, particularly the older motherboards, supporting Dual Channel have the RAM slots color coded.

As such, if you have two RAM modules, place them in slots with the same color.

which ram slot to use featured
RAM slots color coded to indicate dual channel. Gigabyte GA-P67A-UD3

On the motherboard above, for instance, you would occupy slot 1 and 3 for dual channel and then slot 2 and 4 for two sets of dual channel memory.

This technique, however, works only for older motherboards since most of the newer motherboards have all of their RAM slots colored in black for “visual appeal”.

Also Read: Which Motherboards Support DDR5 RAM?

RAM Slot DOES Matter When You Have TWO RAM Modules

Pay attention when you have two RAM modules. You have to make sure that you plug the RAM modules in the correctly indicated slots for dual channel memory to work.

Would Installing Four RAM Sticks Make It Quad Channel?

No, if you have 4 x RAM slots and you occupy all of them, you will NOT have quad-channel memory, instead you will have TWO sets of Dual Channel RAM.

Quad Channel memory require specialized CPU and motherboards. Commercial PCs do not support quad channel RAM.

What if You Only Have a Single RAM Stick?

If you only have a single RAM stick, you can essentially use any slot you want and it wouldn’t matter much because in the end, no matter which slot you plug the RAM stick in, it will conform to single channel only.

What if You Only Have Two RAM Slots?

If you have two RAM slots then it does not matter which one you use.

Essentially, a motherboard with four RAM slots has two sets of dual channel memory. A motherboard with two RAM slots has one set of dual channel memory.

Also Read: What to Do After Upgrading RAM?

Pro Tip: Plan the Capacity of the RAM Sticks to Leverage Dual Channel

When building a PC and when choosing RAM in particular, make sure you leverage the dual channel technology of your motherboard.

So if you plan to install 16 GB of RAM on your PC, then instead of going for a single 16 GB module, get 2 x 8 GB RAM modules.


Does it Matter Which RAM Slot You Use?

Yes, in order to leverage Dual Channel technology, the RAM slot does matter.

Which RAM Slot to Use?

To determine which slot to use first, refer to the motherboard’s manual.

Generally, you should first plug the slot in the second RAM slot, then fourth, then first and then third.

How Do I Know if My RAM is Dual-Channel?

RAM modules do not determine whether they are dual channel or not. Motherboard and the CPU determines whether they support dual, triple or even quad channel.

Any RAM stick can conform to single, dual, triple or quad channel if the motherboard supports the technology.

Also Read: Intel vs AMD RAM – Are RAMs for Intel and AMD CPUs Different?

What if You Have Three RAM Sticks?

As a rule of thumb, a good PC builder should avoid building a PC with an odd number of memory sticks.

Now if you have three RAM sticks, you should have no issues with running them, however, there is a possibility that you two of the RAMs may not leverage the Dual Channel technology.

It all depends upon how good the motherboard is with utilizing the FLEX Mode whereby you have an asymmetrical memory arrangement.

Modern motherboards and CPUs should have no issues dealing with this arrangement. So in Flex mode, two of your memory sticks will run in Dual Channel mode, while the third would work in single channel.

Can I Use Memory Sticks with Different Capacity for Dual Channel?

Say for instance you have a 16 GB and an 8 GB RAM.

You can most certainly use these together for Dual Channel, however, only the common amount of RAM on both sticks will run in Dual Channel.

So for instance, only 8+8 GB of RAM will work in dual channel (partial dual channel), while the rest will work in single channel.

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Atif Qazi
Atif Qazi is the founder of PCGuide101 and an expert in the computer peripheral industry with over two decades of experience. He has worked as a consultant for major companies and has a deep understanding of the inner workings of computer peripherals. He has a degree in Electrical Engineering and has served as a product manager and technical consultant. He is passionate about testing and evaluating the latest products to provide readers with reliable information.

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