Dual channel memory question.

fcdwn777

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Sep 4, 2010
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Hello. First a little background. I have a asrock z77 mobo that had 8 gb of ram in the form of 4, 2 gb sticks. Last night my computer turned off suddenly and when it tried to reboot I got error 55, which is a memory error. It would turn off and turn back on, and then turn off again a few seconds later. If I let this happen enough times it would eventually boot fine, and then anywhere between 15 mins to an hour later it would shut down again, give me error 55 and turn off and on every few seconds.

Through troubleshooting (taking all the ram out and putting it in one stick at a time) it seems that I have found the culprit, one of the sticks has gone bad, even though memtest said everything was fine. Now, since my mobo only supports dual channel, not only did I have to take out the offending stick of ram, but also another to keep the dual channel setup. So now I am down to a sad 4gb of ram which is just not ok.

Finally, here is my question. For a dual channel setup, all 4 sticks don't have to match, right? Only the sticks in A1 and B1 have to match, and the sticks in A2 and B2 have to match. Is this correct? If so my plan is to purchase another 8gb of ram in the form of 2, 4gb sticks for a total of 12gb ram and put them in my currently empty A2 and B2 slots. Before I hit purchase on Newegg I want to make sure that the research I did was correct. Thanks.
 
Solution
Memory timing is a tricky thing and way more complex than what could be answered in a post here. In general you want the same timing parameters on all the RAM. Theoretically, if you can match those parameters they shoudl work fine. Theoretically. Which leads me to my favorite saying, "In theory, there is no difference between theory and practice. In practice, there is."

So you need to get as close as possible in all of the RAM timings as possible if you are going to use different ones. What I'm talking about is the four numbers usually stated somewhere on the ram like 9-9-9-24. Here's a link if you want to dig deeper:
Understanding RAM timings

Also be aware that different manufacturers' sticks may react differently to their...

InvalidError

Titan
Moderator
Ideally you want four matching DIMMs. Most of the time though, should be able to get away with two different pairs of matching DIMMs installed in a symmetrical channel arrangement.

The fewer variables there are, the less likely you are to run into issues.
 

fcdwn777

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I see. I don't like running into issues. So then, from what I see most 12gb ram come in 3 sticks which would not work for my dual channel mobo, so my options are to either 8gb ram or 16 gb ram? 16 seems like such overkill to me, but I don't know if 12gb ram is achievable with a dual channel mobo.
 
Memory timing is a tricky thing and way more complex than what could be answered in a post here. In general you want the same timing parameters on all the RAM. Theoretically, if you can match those parameters they shoudl work fine. Theoretically. Which leads me to my favorite saying, "In theory, there is no difference between theory and practice. In practice, there is."

So you need to get as close as possible in all of the RAM timings as possible if you are going to use different ones. What I'm talking about is the four numbers usually stated somewhere on the ram like 9-9-9-24. Here's a link if you want to dig deeper:
Understanding RAM timings

Also be aware that different manufacturers' sticks may react differently to their environment, mostly heat. That's true even for different batches from the same manufacturer because the production facilities have wear and tear and the end products vary somewhat.

The bottom line is that you may or may not get them to work together and it's almost a sure thing they won't work together at their maximum speeds but 12GB should be better than 8GB. Worst case, you pitch the two 2GB sticks and still have 8GB. Since one of the 2GB sticks has already failed the others may not be far behind.
 
Solution