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jinyoungkim7

macrumors regular
Original poster
Apr 14, 2010
119
8
Maryland, USA
To those of you who opted to get the Late 2015 5k iMac with 8gb and decided to upgrade the RAM themselves. Which RAM sticks did you buy and from where?
 
Kingston Technology HyperX Impact Black 8GB 2133MHz DDR3L 1.35V Laptop Memory (HX321LS11IB2/8)

Bought from Amazon, was only a few dollars more than the type that came with the computer. I have had no issues, and have just liked having the extra memory occasionally.
 
I went with Crucial. Got the 16GB upgrade kit (2 x 8GB) to add to my 8GB iMac.
 
Crucial caused the sleep mode on my 5K to fail. Switched to OWC and had no issues. If you read the comments on Amazon regarding the crucial you will see plenty of issues when mixing Apple and Crucial.
 
Could I steal this thread for a moment regarding RAM for iMacs. I've been searching the internet but I can't really find anything definitive. I'm trying to figure out if it matters which banks/DIMM you put the RAM in in order for it to run dual channel.

Some say you should run your identical twin RAM modules in the same BANK others same DIMM pair.


I upgraded my iMac from 8GB(2x4) to 16GB (2x8) and when I opened the backside the factory sent 2x4GB RAM were placed in slot 2 and 4 and when looking at "about this mac" and "memory", they are top next to each other. And when looking in the sys. info, it says:
BANK0/DIMM0 4GB
BANK1/DIMM0 4GB
BANK0/DIMM1 empty
BANK1/DIMM1 empty

So what I get from this is that the "DIMM0" is paired and not the "BANKS", I don't know...

I simply don't get it really, does it all matter, dual channel or not, pairing or not? Can't find anything about it from Apple themselves...

some help please :)
 
I got mine from OWC and have had no issues at all.
+1 I bought my 27 inch late 2015 (3.3 GHz i5, 2TB Fusion) with 8GB RAM and installed an additional 16GB of OWC RAM. No problems at all, runs great!
 
Could I steal this thread for a moment regarding RAM for iMacs. I've been searching the internet but I can't really find anything definitive. I'm trying to figure out if it matters which banks/DIMM you put the RAM in in order for it to run dual channel.

Some say you should run your identical twin RAM modules in the same BANK others same DIMM pair.


I upgraded my iMac from 8GB(2x4) to 16GB (2x8) and when I opened the backside the factory sent 2x4GB RAM were placed in slot 2 and 4 and when looking at "about this mac" and "memory", they are top next to each other. And when looking in the sys. info, it says:
BANK0/DIMM0 4GB
BANK1/DIMM0 4GB
BANK0/DIMM1 empty
BANK1/DIMM1 empty

So what I get from this is that the "DIMM0" is paired and not the "BANKS", I don't know...

I simply don't get it really, does it all matter, dual channel or not, pairing or not? Can't find anything about it from Apple themselves...

some help please :)
Here is my setup
Screen Shot 2016-01-29 at 6.07.02 PM.png
 
I just received my 32GB of 2133 Kingston HyperX tonight. So I'll be putting it through it's paces of the next week or two to see how the system does.
In my 2013 I have 32GB of Crucial Ballistix and 1 stick ended up going bad a little over a year. I contacted Crucial and they told me to send it back and I received the replacement stick last week with a little over a week turn around from shipping to receiving.
IMG_0858.jpg
Screen Shot 2016-02-07 at 6.51.26 PM.png
 
Could I steal this thread for a moment regarding RAM for iMacs. I've been searching the internet but I can't really find anything definitive. I'm trying to figure out if it matters which banks/DIMM you put the RAM in in order for it to run dual channel.

Some say you should run your identical twin RAM modules in the same BANK others same DIMM pair.


I upgraded my iMac from 8GB(2x4) to 16GB (2x8) and when I opened the backside the factory sent 2x4GB RAM were placed in slot 2 and 4 and when looking at "about this mac" and "memory", they are top next to each other. And when looking in the sys. info, it says:
BANK0/DIMM0 4GB
BANK1/DIMM0 4GB
BANK0/DIMM1 empty
BANK1/DIMM1 empty

So what I get from this is that the "DIMM0" is paired and not the "BANKS", I don't know...

I simply don't get it really, does it all matter, dual channel or not, pairing or not? Can't find anything about it from Apple themselves...

some help please :)

I think you're right, it's the DIMM0/1 slots that must be paired, not the banks. Mine came with the stock 8GB placed like yours. I just upgraded to my 2x8GB Kingston HyperX 2133 and placed them in the same Bank (lower 2 slots...ended up being BANK1). I ran Geekbench and was surprised to see lower scores than with the stock RAM, pulled down by the memory scores (which across the board were 1000 points, or ~33%, lower than initially). I suspect I'm not getting dual channel and will reinsert in the same configuration as factory (i.e. slots 1 and 3 or 2 and 4).

EDIT: Confirmed, the dual-channel is between DIMM#, not Bank#. Swapped my RAM around and got the expected boost in Geekbench above my factory specs. FYI, from top to bottom as you look at the physical compartment, the RAM slots are:

BANK0/DIMM1 [top]
BANK0/DIMM0
BANK1/DIMM1
BANK1/DIMM0 [bottom]

Not what I would have expected, but there it is.
 
Last edited:
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