Installing RAM modules from different kits

[White Rabbit]

I have two sets of 2x4GB modules (for a total of four modules and 16GB of RAM), both of them are of the model number CMX8GX3M2A1333C9.

I've been running into some BSODs lately, and decided to run memtest86 on each of the four modules. Only one produced errors, and when I took it out, the BSODs stopped.

However, now I only have 12GBs of RAM, so I wish to buy a single 4GB module, CMX4GX3M1A1333C9, which for all intents and purposes is basically half of a two-module kit. I see zero difference in the specifications. But...Corsair doesn't agree:

Each kit of Corsair Memory is tested to run at its advertised settings in the configuration in which they are sold.  If you purchase a 4GB kit (2x2GB), then we can only guarantee its performance and compatibility when using it as a single kit.  To ensure the best results with more than two memory modules installed in the same system, it is best to get a kit which has been tested to run in that configuration.

While it is definitely possible that two kits would run together in the same system, there is a chance that you may need to reduce the speed of the memory due to motherboard chipset limitations when populating more than one memory module per channel on the board.  If you have problems mixing sets, it is suggested to manually lower the frequency of the memory.

Is this going to be a problem? I certainly didn't have a problem, apart from the one faulty module, when running two 2x4GB kits together. Is it too much to expect that a 2x4GB + 1x4GB + half a 2x4GB RAM configuration will work? Because as far as I can see, the numbers add up to 4x4GB...

My motherboard is an mATX MSI Z97M GAMING, and my CPU is an i7 4790K.

 

[Agazed]

Yea it will work fine.

[Clear17Mud]

do you still have a warranty on that stick? because to rma it would probably be less then another stick.

[White Rabbit]

Yea it will work fine.

Ok, but why does Corsair guarantee that a 4x4GB kit will work, but not 2x2x4GB or 4x1x4GB?

[manikyath]

the difference between buying two (identical) individual sticks, and a kit of two skicks is that the kit is factory tested to work together.

 

its not magic that makes it work, its a reassurance it'll work, other than just going on the specs being the same.

[White Rabbit]

Well, it turns out one kit is version 7.25 (bought last month), and the other version is 7.21 (bought in 2013), so they are not really the same, despite having identical model numbers. I did not even think to check before I bought the new RAM, unfortunately. Apparently this can lead to stability issues down the road, especially if I want to overclock.

I'm just going to RMA the new module, take out the remaining new module, and keep using the two old ones in 8GB dual-channel mode. If the RMA is successful, I'll have two sets of probably incompatible 2x4GB RAM, which is still fine. I'll eventually upgrade to 16GB for my main computer, and use the two sets of 2x4GB RAM in two other separate builds at a later date.

[White Rabbit]

Yea it will work fine.

That's not what I've been told on the Corsair forum.

 

This is the reply I got from a Corsair employee

http://forum.corsair.com/v3/showthread.php?p=781775#post781775

 

Ok, I know that Corsair really wants people to buy their memory sticks, but am I to understand (using an example), that if if buy a 2x4GB RAM kit today, and want to upgrade to 8GB of RAM with a second 2x4GB RAM kit a few years later, then the two are not guaranteed to be compatible? I have to buy a brand new 4x4GB RAM kit, leaving behind my old 2x4GB RAM as just dead weight???

Yes, two sets of RAM are not guaranteed to be compatible, because they are not tested together to begin with. That's pretty standard among DRAM manufacturer.  

But like what we have mentioned in our FAQ, while it is possible to combine sets of RAM, you may need to tweak settings in your MB BIOS to make it work.

 

Note that I made a typo in my post. I meant to write "upgrade to 16GB of RAM". Obviously upgrading from 8GB to 8GB makes no sense.

[Agazed]

That's not what I've been told on the Corsair forum.

 

This is the reply I got from a Corsair employee

http://forum.corsair.com/v3/showthread.php?p=781775#post781775

 

 

Note that I made a typo in my post. I meant to write "upgrade to 16GB of RAM". Obviously upgrading from 8GB to 8GB makes no sense.

 

Yes, they arent tested together but there is no reason why they wouldnt work together. As long as they are the same type and speed, they will work FINE 99.9999% of the time.