Matching SODIMM sticks

Hey guys,
was wondering, if a laptop comes with a 2GB DDR3 memory stick, can I add in a 4GB DDR3 stick from another manufacturer and have them work together for 6GB in total? I'll of course make sure the frequency/latency/timings are all matching. Would the fact that they're not identical make it impossible for the RAM to run in dual channel mode?

Thanks

 

If you are going to go with different rams, try your best to match the default timings and voltage, as well as the speed, and in the best case, your ram chips. The more of these variables that match, the better your chances of being able to run in dual-channel mode.

Though I don't think this is possible on notebooks, because it would have to be in a configuration like this to work, and this is on a desktop...
2GBx2 should be in one bank, 2GBx1 in the other bank.

Although, I don't know if Intel has implemented this in the Notebook boards because they only usually have 2 SODIMM slots, but they used to have something called "Flex Mode" that would use a portion as Dual Channel, and a portion as Single Channel.

 

I see. I don't that bank method is used for this, as, like you said, there are only two slots.

Well, how would I tell, actually? I mean if I get a chip, how do I test that it's running in dual channel mode or not?

 

CPUid should be able to tell you what mode is currently being used, under the RAM tab.

 

For dual channel mode to work, I believe you need sticks of the same size - so with a 2GB + 4GB layout, you won't get dual channel mode. Honestly, though, the performance difference is minimal, so if you need 6GB of memory, that should work fine provided the sticks have the same speed and CAS latency specs.

 

Is that right? So for general daily use, gaming, etc, I won't notice the difference between dual channel mode or not?

XGX, does that work well? I was looking at this HP with 1 + 2GB sticks, totally mismatched brands, etc, it still said dual channel.

 

None of this matters. Ram always defaults to the least common denominator, so all sticks will run at the exact same timings and voltages. If the same amount of memory is in each channel, it will run in dual channel mode.

If the memory channels don't have the same amount of memory, it will still attempt to run as much of it in dual channel as possible, the flex mode you speak of. It isn't something they used to have, it is something they do have.

Midnightsun is correct about the performance difference. Whether you run in full dual channel, partial (flex mode), or single channel, it makes little to no performance difference.

 

I thought they still had that, but wasn't sure.

 

As long as their are 2 sticks, it will run in dual channel mode. If the two sticks match it's called synchronous, otherwise it will run asynchronously. Synchronous will be better than asynchronous, which in turn will be better than single channel - but only in benchmarks. The only other time you will notice a difference is for integrated graphics.

 

Oh, I see. So the notebook I am wondering about has an HD5650 card in it. I should be able to just buy another 4GB stick and it will work fine with the 2GB one, right?

 

Have a 4GB and 2GB stick in my Sony FW - been running it without issue for over 2 months now. Works fine.

 

It should work fine, though I have to ask, why do you need more than 4GB?

 

It's like this. A laptop I'm getting (already bought, just need to pick it up) has a single 2GB stick in there. I figured I could either put a 2GB in there or a 4GB: if I put a 4GB in there then if I want to upgrade to 8GB is easier in the future, right? Hehe

 

Yes, if you need to upgrade to 8GB in the future. By the time most notebooks will have/need more than 4GB of RAM, your other components will be obsolete anyway. Just add a cheap 2GB stick, and you'll be just fine unless you have specific needs for large amounts of RAM, which it seems like you do not have.

 

Alright. Thanks~