What RAM works with other RAM?

Hello... Yes, you can do 12gb, they must be put in the proper memory slots in your future MB, read the manual section on that motherboard for information... You also need a 64 bit OS for them to be used... Samsung is a great memory chip company, But you could use another well reviewed brand... I would get similar timing sticks, either 1333 or 1600 will work.

As I mentioned earlier, first, you determine the speed of your controller.

You can also struggle that all channels have the same amount of memory. Because, you know, when one channel has all the memory, say 100 GB of memory, while others are loaded only with symbolic amount, say 1 KB of memory, you effectively have only one channel. Just because all memory accesses will access only the first channel and other channels will have no effect.

Everybody will tell you that memories must have identical timing. This is bullshit. Faster memory (1666MHz) can work at lower rate (1333MHz). Fuck them. This is a religous sect. They do not understand the technology and broadcast misconceptions. Some of them keep you on the safe side (e.g. use only memory kits). Others are bullshit, like "use the same timing everywhere". Actually, the logic suggests that it is better to have mismatched timing, e.g. 2100 MHz + 1333 MHz than two low-timing memories. As I explained in superuser, unganged memory controllers operate memories independently. So, if you replace two channels, ch1:1333 + ch2:1333, with ch1:1333 +ch2:2100. Unganged controller will access the second channel twice faster. You can install twice much memory there for balancing the load.

It is even more bullshit in cases like yours, where you add more sticks (in to the channels wich already have some sticks attached). Look at my 7-7-7 vs. 8-8-8 problem. The timings degrade because channels are parallel -- the memory sticks in parallel channels are peer-to-peer physically connected only to the memory controller respective channel. When memory or controller drives a logic 1 or 0 to the peer, this takes some time because the transisor at the other end has capacity and charging a capacitor takes time. If you plug another stick into the same slot, you'll have two receiving capacitors, driven by the same old memory or controller transistor. This means that swtching (communication speed) can drop significantly. The 1333 memories are slow. This means that they have larger capasistance. It is better to combine two 1666 memories to one 1333 controller (channel). It is even better to combine 1333 with 2100. Combinging 1333 memories with some faster memories is more likely to operate at 1333. When you combine 1333 with "matching" 1333, you have more chance of timings degradation. I mean that 1333 controller is sorta intended to operate at 1333 mhz with 1333 memories with the timings, memory specified latencies, e.g. 8-8-8. However, when you have multiple 1333 memories in one channel, the performance is not guaranteed. You'll either to degrade the frequency or increase latencies. Combinding slow memory with fast, you have higher chance that no degradation occurs.

I say that taking faster memory favours the lower performance degradation. I cannot say how much is the effects. I may also overlook something, but, those who claim that it is better to combine 1333 with other 1333, do not have clue at all.

Mixing DRAM can definitely be problematic, yo are taking a good approach though, getting the 8GB you want and need, once you have them go ahead and try your other DRAM with it, there's no guarantee they even play together, but if any problems, give me a shout, can often get them to play with minor voltage/timing adjustments