Dual Channel vs Quad Channel?

[wagaloo123]

Could someone explain dual channel vs. quad channel? Does it affect mobo compatibility, upgrading ability later on, speed, etc.

 

Thanks!

[typographie]

X99 systems (i7-5820K and above) support quad-channel mode if all of the DIMMs are installed in matching sets of four. It is double the bandwidth of dual-channel, which is in turn double the bandwidth of a single channel. Most other systems support dual-channel, which requires all DIMMs are installed in matching pairs.

 

As far as upgrading, you just need to make sure you plan around the requirements of dual/quad-channel modes. As far as I know, motherboards always come with enough slots for the memory modes their compatible CPUs support, so it doesn't really affect that decision.

[Naeaes]

ELI5:

If you think of the data link between the CPU and the RAM as a highway, the speed of the cars on it would be your RAM speed and the number of lanes would be your RAM bandwidth. The more data you have, the more cars and so forth. 

A single car can't get there any faster no matter how many lanes there are available. It can only occupy the single lane and travel at the speed limit. But four cars can travel a four-lane road side by side just as fast as a single car on a single lane. So, while more bandwidth doesn't technically make anything move any faster, you get more data though in the same amount of time the more bandwidth you have.

[vanished]

One thing to remember is that this is separate from how many memory sticks you actually have installed.  If you fill the slots on a Z170 system (4 DIMMs), that's still only Dual Channel.

 

It also doesn't limit compatibility in any way - you can use one stick of RAM in a system that supports quad channel or use 4 sticks in a system that supports dual channel.  The only reason to consider it is to make sure you're getting the best possible performance.

[wagaloo123]

1 hour ago, Ryan_Vickers said:

One thing to remember is that this is separate from how many memory sticks you actually have installed.  If you fill the slots on a Z170 system (4 DIMMs), that's still only Dual Channel.

 

It also doesn't limit compatibility in any way - you can use one stick of RAM in a system that supports quad channel or use 4 sticks in a system that supports dual channel.  The only reason to consider it is to make sure you're getting the best possible performance.

This is super helpful, thanks!

[vanished]

2 minutes ago, wagaloo123 said:

This is super helpful, thanks!

And I should also just add on that what setup you are running depends on the CPU, motherboard, and what memory is installed.  IF you have a system that supports quad channel but you only plug in one stick of memory, that would only be running in single channel.  If you have a system that supports dual channel and you plug in four sticks of RAM, that's still only dual channel.