Can I mix Dual channel and Single channel RAM?

[poortechnic]

I upgraded my Alienware 17 R3 laptop with a 1x 16GB DDR4 Crucial 2133mhz Dual Channel RAM from a 2x 4GB 2133mhz ram.


The computer clerk guy removed the two 2x 4GB DDR4 Hynix 2133mhz Single Channel RAM and leaving one ram slot unused. I tried putting in 1x 4GB on the remaining slot because i have nowhere to store it and to my surprise, it worked

The thing is many are saying that i shouldn't mix to different channel rams as there are consequences for that configuration. Can you give me more info about this. Thanks

 

[CountMike]

I think that somebody mixed terms Single/double Channel and single/double sided memory.
Single/double Channel is BIOS function and is rarely found option in laptops. It requires two exactly same memory modules in the same channel of processors IMC (integrated Memory Controller).

 

[madmatt30]

There is no such thing as single or dual channel ram on a physical level.
Ram is ram.

Its the motherboard that configured ram as single or dual.

To run dual channel you need 2 matching (identical in size) sticks in each slot

Your 2 x4gb would have been running dual channel.
A single 16gb stick will run single channel
A 16gb + 4gb stick will run single channel.

There's a 5-10% performance drop off going from dual channel to single channel depending on use.

You 'should' have gone for 2 x 8gb sticks for optimal performance really if possible.

If you want to keep the 4gb stick in there for 20gb total you can do, there aren't really any negatives doing so.