Late 2015 5K iMac RAM

[TheBro72]

I'm days from ordering a Late 2015 5K iMac with 1TB SSD, 4.0GHz i7, M395X. As we all know RAM is far cheaper bought separately, so I've looked on amazon and found some RAM at a very good price.

I've read this on an earlier thread today:

"Another thing to consider which has a far less impact is using the memory bank channels properly. Never put an odd number of RAM sticks in your computer (the exception being 1 stick of RAM). If you look at where your RAM goes (say you have 4 slots like on the back of an iMac) you will see numbers listed, most of the time the order is something like 1, 3, 2, 4. This is based on dual channel memory, 1 and 2 is where your first two sticks go, 3 and 4 is where the last two sticks go. If you are going for 8 GB of memory you might use 4 GB x2 in slots 1 and 2, but if you had 4 sticks of 2 GB in all 4 slots, you'd get a slightly higher performance boost. For 16 GB you'd use 4 x 4GB and for 32 GB you should use 4 x 8 GB."

Is this correct? I'm looking 32GB of RAM for 3D rendering & video editing

 

[CWallace]

Yes, the Intel chipsets support memory interleaving so 4x8GB can provide a bit better memory performance than 2x16GB (provided all other things like timing and such are identical between the 8GB and 16GB DIMMs).

http://www.intel.com/content/www/us/en/support/boards-and-kits/000005657.html

 

[TheBro72]

Ok cool, thanks.

When I went into the apple store I told the "specialist" what my needs where. I'd already decided on a 27" iMac for many reasons, but I wanted to know if/how the additional video memory of the 395x to the 395 would benefit me and shock, he couldn't tell me because he "really didn't know".

Is it worth the extra £200?

I've always believed you should spec any machine as high as you can afford to, so you are not cursing yourself 4/5 years down the line when performance is starting to drop. My rendering work is going to get busier and apart from buying a external SSD in the future (when the prices are more reasonable), I want to try and get up to 10 years out of this machine. However are there big differences between the performance of the 395 with 2GB memory and the 395X with 4Gb memory to warrant the additional costs?