Sidebar Sidebar
Become a MacRumors Supporter for $50/year with no ads, ability to filter front page stories, and private forums.

iMac RAM Mixing (2x2GB + 2x4GB)

J

JimmyDThing

macrumors regular
Original poster
Aug 23, 2007
208
0
I know that this has been asked a lot, but I haven't anything that really answers my question.

I'm going to be getting an iMac 27" when they come out and just get the stock 2x2GB sticks of RAM that come with it. I want to upgrade to 8GB... but I'm doing 2x4GB so that if I ever decided I wanted to do 16GB (I don't see why, but why not at least have half of it?).

My question is, if I do this, should I leave the 2x2GB sticks in with the 2x4GB sticks? Or should I take them out?

There seems to be some conflicting ideas about what RAM to use. I know you're supposed to do it in pairs, but I don't know how the iMac handles having 4 slots.

My guess would be that it's best to use 2 or 4 sticks that are the same, I'm not sure about 1 or 3. But what about having 2 pairs that are different as noted above?

Any insight would be helpful.

Thanks!
 
Leave the RAM there. You don't have to use pairs and iMac doesn't support dual channeling so you won't even get any boost from it. 12GB is still 33% more than 8GB
 
Hellhammer said:
Leave the RAM there. You don't have to use pairs and iMac doesn't support dual channeling so you won't even get any boost from it. 12GB is still 33% more than 8GB
Click to expand...

Are you positive that the imac doesn't use dual channeling? I know its not a huge boost but this just surprises me.
 
Thanks a ton!

I saw some people saying that you get the speed of the slowest stick or pair, but I knew that couldn't be. But I did know there was some advantage to keeping things in pairs.

I want to understand it better so I can make more informed decisions when buying RAM. Why is it advantageous to keep sticks in pairs? Part of me has wondered if maybe each processor gets a stick, but I'm a total n00b when it comes to how hardware works with each other. I just know each part and it's job, no clue how they work together.
 
richprice79 said:
Are you positive that the imac doesn't use dual channeling? I know its not a huge boost but this just surprises me.
Click to expand...

Ummhh... Did I sound like I am? Actually because iMacs use Core i7 CPUs now as well, it would have to be triple channeling. Channeling wouldn't make any difference on matching unpaired chips though
 
JimmyDThing said:
Thanks a ton!

I saw some people saying that you get the speed of the slowest stick or pair, but I knew that couldn't be. But I did know there was some advantage to keeping things in pairs.

I want to understand it better so I can make more informed decisions when buying RAM. Why is it advantageous to keep sticks in pairs? Part of me has wondered if maybe each processor gets a stick, but I'm a total n00b when it comes to how hardware works with each other. I just know each part and it's job, no clue how they work together.
Click to expand...

Some older Macs can only utilize RAM which is in pairs so you couldn't mix 1GB and 2GB together, but I don't know why was that, looks like technology has developed. Anyway, unpaired chips works flawlessly in current Macs
 
Hellhammer first of all I always enjoy your input as your very helpful but this is the article was what i was basing my assumption on regarding dual channel and i7

Lynnfield Reaches Retail

Last week Intel's latest addition to its arsenal of desktop processors was released in the form of the Core i7 and Core i5 series' for the LGA1156 socket. These new cores, previously known as Lynnfield (and we will still call it as much throughout our reviews), differ from the previously available Bloomfield processors (only available as Core i7 CPUs for the LGA1366 socket) in a few ways:

Dual-channel memory controller- Lynnfield does indeed still have an integrated DDR3 memory controller but here Intel has removed one of the channels from Nehalem to make the new core dual-channel. While this is theoretically a performance drawback, in real-world testing (as you will soon see) the third channel made very little performance difference in most consumer applications. By removing one channel Intel was able to make the CPU package smaller (less pins required), lower the cost of ownership (only two DIMMs needed now) while keeping performance very high.

source http://www.pcper.com/article.php?aid=781
 
richprice79 said:
Hellhammer first of all I always enjoy your input as your very helpful but this is the article was what i was basing my assumption on regarding dual channel and i7

Lynnfield Reaches Retail

Last week Intel's latest addition to its arsenal of desktop processors was released in the form of the Core i7 and Core i5 series' for the LGA1156 socket. These new cores, previously known as Lynnfield (and we will still call it as much throughout our reviews), differ from the previously available Bloomfield processors (only available as Core i7 CPUs for the LGA1366 socket) in a few ways:

Dual-channel memory controller- Lynnfield does indeed still have an integrated DDR3 memory controller but here Intel has removed one of the channels from Nehalem to make the new core dual-channel. While this is theoretically a performance drawback, in real-world testing (as you will soon see) the third channel made very little performance difference in most consumer applications. By removing one channel Intel was able to make the CPU package smaller (less pins required), lower the cost of ownership (only two DIMMs needed now) while keeping performance very high.

source http://www.pcper.com/article.php?aid=781
Click to expand...

Hmm.. Interesting! So Lynnfield support dual-channel but not triple? By the way, would dual-channeling work in both pairs (e.g. 2x1GB & 2x2GB) or only in one pair?

Maybe Apple has blocked dual/triple-channeling with firmware because none of the iMacs support it (as far as I know) or logic board doesn't support it.
 
From my understanding of it the ram has to all be the same speed but not the same size. So if you have 2x4 and 2x2 you should be fine. As long as you have 2 sticks of equal size and speed and then 2 additional sticks of the same speed but not necessarily size you should be running in dual channel. Not all cpu's have onboard memory controllers but the the i7 has an one integrated into the cpu so this should be working on the new imac.
 
richprice79 said:
From my understanding of it the ram has to all be the same speed but not the same size. So if you have 2x4 and 2x2 you should be fine. As long as you have 2 sticks of equal size and speed and then 2 additional sticks of the same speed but not necessarily size you should be running in dual channel. Not all cpu's have onboard memory controllers but the the i7 has an one integrated into the cpu so this should be working on the new imac.
Click to expand...

Maybe, Maybe... Crucial (big RAM brand) says iMacs don't support dual-channel but MacRumors guide says yes

All Intel Core Macs support dual channel memory access if matching modules are installed. The customary estimate is that this gives a 6% - 8% real world performance benefit. The modules do not have to be the same brand. That means it is quite possible but not 100% guaranteed, that adding a 3rd party SODIMM to an Apple supplied SODIMM of the same size will make a matched pair.
Click to expand...

Anyway, extra 4GB will speed up more than dual/triple-channeling would though.
 
Manufacturer Mixing

To dig up an old thread so as to not start a new one...

I am doing the same thing as the original poster. 27" iMac w/ stock 2x2GB and then adding 2x4GB.

I have seen conflicting reports about manufacturer mixing. Some say fine. Some say don't.

I am on the fine to do camp, but I wanted to make sure. Ok to mix manufacturers?

I was thinking of either going with:

NuRAM from Owc ( http://eshop.macsales.com/item/Newer Technology/8566DDR3S8GP/ ) or

Mushkin Enhanced from Newegg ( http://www.newegg.com/Product/Product.aspx?Item=N82E16820226015 ) .... although on the summary page it says this Mushkin memory is for Apple Notebooks; but I assumed that was wrong and it is for both Notebooks and iMacs. True?

Thanks.
 
Does anyone know which of these chips apple uses in the current imac models (Apple/Micron or Apple/Hynix). Is one better then then other? All chips are not created equal?
 
You must log in or register to reply here.
Register on MacRumors! This sidebar will go away, and you'll see fewer ads.
Top Bottom
Back