Installing memory modules - at same color or next to each other?

Question

Many motherboards have 4 slots for memory DIMM modules, arranged as follows:

• Slot with plastic having color #1
• Slot with plastic having color #2
• physical space
• Slot with plastic having color #1
• Slot with plastic having color #2

_{(source: quoracdn.net)}

Now, if I got a kit of 2 DIMMs, in which of the following configurations should I install them (to reap the benefits of dual-channel access)?

• Always in adjacent slots, but with differring color
• Always in non-adjacent slots but with the same color
• Wherever I like, since it doesn't matter
• In first or the second option, but the right choice is motherboard-dependent

(I realize it's possible that the motherboard's manual has the answer, but I want to know if there's a general rule or not.)

Answer 1

As noted, check your motherboard manual.

In general though: Populate the RAM slots starting from the slot furthest from the CPU. This is your "Always in adjacent slots, but with differring color" option.

The different colours signify the channel used for the RAM in that slot - so in a Dual channel system, there are two colours, and three in a triple channel system. For performance, you should be using both channels, so if you have two dimms, this rule of thumb will result in one slot for each channel being filled first.

note: "Furthest from the CPU" comes from the motherboard manual of my recent PC build (ASUS motherboard) and may not be what is stated for all motherboards. The key point however is to fill the different memory channels equally, and this is likely provided as an 'idiot-proof' instruction, rather than instructing the user to just fill the channels equally. In practice, as long as the channels are equally filled, I believe there should be no performance or capacity limitations.