Installing modules from different kits

[thenoseknows]

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.

 

[drescherjm]

Is this going to be a problem?

Most likely you will be fine.

 

[cyclone3d]

To add to what drescherjm said, although it should be fine, if they made a revision to the RAM at some point, they may have slightly different specs and/or sub-timings which could lead to issues.

What about getting your faulty stick replaced under warranty? It has a lifetime warranty.

 

[Tsumi]

The issues really only pop up when trying to get the max out of the RAM. Drop it down a notch or two, or bump the voltage, and most issues should go away.

 

[thenoseknows]

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.

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.

 

[DejaWiz]

The revisions shouldn't matter as long as the specs are the same. You have a bad DIMM.

Buying the single module will not cause any problems.

 

[larrymoencurly]

I think there's a good chance it'll work fine and in dual channel mode because that's been my experience, provided the sizes matched, including in one case when I messed up the SPD of one module, meaning the SPD of the other module was used for both. The last time mismatched memory caused trouble for me was with a late 1990s Socket 7 motherboard.

 

[thenoseknows]

This is the reply I got on the Corsair forum:
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.

 

[DejaWiz]

It's still marketing FUD. OEM's, even those with premium/performance brands (eg- Alienware), sell their modules individually. With JEDEC specs and standards being pretty tight nowadays, there is no reason why there should be any concern about buying multiple multi-module kits, let alone a bunch of individual modules.

 

[Joseph_Ocbina]

It's still marketing FUD. OEM's, even those with premium/performance brands (eg- Alienware), sell their modules individually. With JEDEC specs and standards being pretty tight nowadays, there is no reason why there should be any concern about buying multiple multi-module kits, let alone a bunch of individual modules.

Exactly my mindset before joining Corsair, but later found out that there are actually good reason why we do not recommend it. As much as we wanted to say "Yes, mixing sets of RAM is guaranteed", we just simply can't due to various technical reasons. The best thing we can say is, it may or may not - mixing sets is always going to be a hit and miss. I have mixed sets myself (same brands and different brands) and the outcome is not always the same. There are times where no matter how much tweaking I do in the BIOS, the sets would just not work together. And other times, I'd just load default settings in BIOS and system boots right away with no problem and stable as a rock.

Keep in mind that we are not condemning mixing sets of RAM, our position is simply that we cannot guarantee it because they are not tested to operate in that configuration. You are always welcome to try it, but in an event that they don't work, like what I said on that post, you probably just have to play around with some settings in BIOS to make two kits work together.

We even said it on our FAQ page:

http://www.corsair.com/en-us/support/faqs/memory

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.