Question on RAM upgrade

[i might imac]

I just ordered an imac with 16GB 2400MHz DDR4.

Am i correct in believing that it has two 8GB modules and if i want to upgrade to 32 GB I would need two more 8 GB modules to fill the remaining two slots.

Am I also correct in saying that I should NOT mix and match module sizes, say two 8GB's in two slots and two 16GB modules in the other two slots. I guess I am asking if all the modules should be the same in all four slots.

Thanks for your help but I am not a computer wiz by any stretch, sorry if this is a dumb questions. Also this is a warning, there will be more dumb questions.

 

[MCAsan]

I ordered our iMacs with 8GB. I ordered two 16GB kits made by Crucial. Booted up without error with 24GB for less cost that 16GB from Apple. Zero problem having two 8GB and two 4GB memory cards.

 

[SaSaSushi]

Am i correct in believing that it has two 8GB modules and if i want to upgrade to 32 GB I would need two more 8 GB modules to fill the remaining two slots.

You are correct, sir. (or ma'am)

Am I also correct in saying that I should NOT mix and match module sizes, say two 8GB's in two slots and two 16GB modules in the other two slots. I guess I am asking if all the modules should be the same in all four slots.

It is best to add RAM in matching sets for optimal performance (dual channel configuration).

When you pop the hood of the RAM hatch on the back of your new iMac you will see that the Apple RAM is installed in alternating slots. Just add the new RAM into the empty ones. As long as the RAM you are adding is a matching set of compatible memory it doesn't matter if it is 4GB, 8GB or 16GB modules. I added two 16GB modules to the 8GB (2x4GB) that came with my 2017 iMac and have been running 40GB with no problems.

Thanks for your help but I am not a computer wiz by any stretch, sorry if this is a dumb questions. Also this is a warning, there will be more dumb questions.

The only dumb question was the one you didn't ask.

 

[i might imac]

Thanks for the replies, both are very helpful.
[doublepost=1511576701][/doublepost]One more question on this subject.

After buying the proper memory from crucial do I just turn off the computer and install or do I need to format these new cards in some way...Hopefully crucial gives dummy instructions for dummies.

 

[enricoclaudio]

Thanks for the replies, both are very helpful.
[doublepost=1511576701][/doublepost]One more question on this subject.

After buying the proper memory from crucial do I just turn off the computer and install or do I need to format these new cards in some way...Hopefully crucial gives dummy instructions for dummies.

Just turn the iMac off and unplug the power cable from the iMac. Install the new Crucial memory and turn the iMac back ON. Sometimes takes about 30 sec for the iMac to recognize the new memory. I installed 16GB (2 x 8GB) of Crucial memory in my new 27" iMac 5K mid-2017 with 8GB base memory. I did the memory upgrade right after unpacking the iMac so from the first start the iMac is running 24GB without any issue. Thats was about 4 weeks ago.