Are different RAM Brands compatible?

[Faltri]

I have an Apacer 8GB DDR4 2133MHz RAM Stick, I want to know if it is compatible with other RAM brands like Crucial 8GB DDR4 2133MHz. I know they have different looks and it will look crap, but I have a closed case anyways.

[Septimus]

Short answer: Yes

Long answer: 

Since they're the same speed, the process will be a little bit easier, but in order to achieve a fully symmetric kit of RAM, you should set the CAS latency and stuff like that to be the same. I'm fairly certain you don't need to do that in order for it to work, but I would double-check me on that. 

[monotron]

Yes, in theory, but you lose any guarantee that the kits will work reliably together, and installing one stick might affect the capabilities of the other (i.e. it might run at a slower timing to accommodate a slower stick). If you install it, the worst that can happen is your system no longer POSTs - in that case, you simply just remove it from your system.

[vanished]

They should (might) work but you increase the chance of problems when you mix stuff

[ARikozuM]

Yes, they [should] work. 

 

Keep in mind that your slots will run at the slowest speed of the sticks in use.

Channels with run timings at the lowest values of the DIMMs in that channel, i.e. channel A's timings can be different to channel B's. 

You can have 2x4GB sticks in dual-channel, but you can also mix 4GB and 8GB in the same channel with 4GB from each DIMM acting in dual-channel and the remaining 4GB running in single-channel (known as flex-channel or -mode)

 

[STRMfrmXMN]

I've used systems with four different DIMMS in the various slots. It ran fine, albeit with looser timings and the speed of the memory was based on the slowest of the bunch.

 

It's something you can do but only if you must.