New RAM in iMac 27 2011 - using dual channel ?!?

[CHSeifert]

I was lazy and kept using my then new iMac from June 2011 with the built in 2x4 GB factory ram and kept the extra 2x4 Corsair laptop ram, I bought, in my drawer until I felt the need for more ram.

Now I've started using Photoshop, Dreamweaver, illustrator and some video editing and need my 8 extra GB of RAM.

But I want to make sure my 2 x 4 Gb ram from Corsair is installed so that they are in the same channel and the 2 x 4 Gb ram from Apple are in their channel. This because I've heard this will make the chances of everything running smoothly larger.

Is this rubbish and should I just open the ram door and install my 2 new block in the 2 empty ram slots and turn it on. Or can I optimise my chances of everything running smoothly by placing my 2 Corsair in either the 2 left/right slots or in the 2 upper/lower slots ?

Thanks in advance.

I did a search, but for some reason didn't find any answers to this exact situation.

 

[The-Pro]

the apple instructions for upgrading the ram dosnt specify.
Also the difference in performance for dual channel to not dual channel is like 5%.
I think if you have one or three modules then dual channel would not be used. 2 or 4 modules will work in dual channel. As long as the new ram is the same spec as the original the performance of the ram wont change

 

[CHSeifert]

the apple instructions for upgrading the ram dosnt specify.
Also the difference in performance for dual channel to not dual channel is like 5%.
I think if you have one or three modules then dual channel would not be used. 2 or 4 modules will work in dual channel. As long as the new ram is the same spec as the original the performance of the ram wont change

But I want my Corsair in the 'same' channel and the 'Apple' factory ram, which probably are Samsung ram, in their channel to optimise chances of everything running instead of having to reinstall the ram several times....

 

[The-Pro]

Nothing to worry about. Just pop them in, unless the RAM is incompatible or defective then it will work. You wont need to reinstall them several times.
So many people on these forums have installed RAM in their iMac, they all just popped them into the free slots, and I have yet to see someone (with compatible, and not defective RAM) write it dosnt work.

 

[NMF]

You're confused by how the dual channel stuff works. Your 2x4gb Apple sticks are dual channel with each other. The only thing you need to worry about is making sure your 2 new sticks are also a pair. You can have two different "pairs" of sticks. For example, in my iMac I have the 2x2gb Apple sticks and then 2x4gb Corsair sticks for a total of 12gb. I'm running dual channel.

The stock Apple RAM is installed in the correct slots. Do you really think Apple would install it in the wrong place? When you open your RAM compartment you'll have two empty slots. Stick the Corsair RAM in there.

 

[CHSeifert]

You're confused by how the dual channel stuff works. Your 2x4gb Apple sticks are dual channel with each other. The only thing you need to worry about is making sure your 2 new sticks are also a pair. You can have two different "pairs" of sticks. For example, in my iMac I have the 2x2gb Apple sticks and then 2x4gb Corsair sticks for a total of 12gb. I'm running dual channel.

The stock Apple RAM is installed in the correct slots. Do you really think Apple would install it in the wrong place? When you open your RAM compartment you'll have two empty slots. Stick the Corsair RAM in there.

Of course Apple know how to install Ram.
It just happen so that in order to use dual channel with 2 sticks of ram, you install 1 stick in each channel.

When you install 4 sticks, I would think the logic and most safe thing wad to install the two Apple installed ram in the same channel and my corsair in the other channel.

That's all

I'm probably overthinking this but as a former PC builder for several years, I know it does play a role where you place your ram if you have 2 sticks from one oem and 2 other sticks from a second oem.

 

[lexar]

Is there some test or utility that can tell you if you are running in dual channel or not?

 

[leman]

Please note that unforeseen incompatibilities may arise. My iMac suffered random crashes when I had 2x original Apple (Samsung) sticks + 2x Corsair sticks in it; I removed the Apple RAM and now it runs stable. Other users didn't have this problem. So its also a question of luck in some regard...

As to dual-channel: the RAM sticks in parallel slots are paired and will work in dual-channel mode. That is, when looking at the ram slots from above, the pairs are:

--1-- --1--
--2-- --2--

So just arrange the matching sticks horizontally and not vertically.

 

[CHSeifert]

Please note that unforeseen incompatibilities may arise. My iMac suffered random crashes when I had 2x original Apple (Samsung) sticks + 2x Corsair sticks in it; I removed the Apple RAM and now it runs stable. Other users didn't have this problem. So its also a question of luck in some regard...

As to dual-channel: the RAM sticks in parallel slots are paired and will work in dual-channel mode. That is, when looking at the ram slots from above, the pairs are:

--1-- --1--
--2-- --2--

So just arrange the matching sticks horizontally and not vertically.

THANKS A BUNCH !!!!!

Exactly the information I was looking for

Not stories about Apple installing their ram correctly - but a tip from a guy, who actually knows what ram channels are and that they need to be arranged accordingly !