For the record, the mid-2017 iMac 5K Memory is User Upgradeable

[CWallace]

Since there is a fair bit of confusion and misinformation (from Apple Chat discussions) about the new mid-2017 iMac 5K, here is Apple's updated Support Document for memory upgrades:

https://support.apple.com/en-us/HT201191

iMac (Retina 5K, 27-inch, 2017)
Get memory specifications for iMac (Retina 5K, 27-inch, 2017), then learn how to install memory in this model.

Memory specifications
This iMac model feature Synchronous Dynamic Random-Access Memory (SDRAM) slots near the bottom of the computer with these memory specifications:

Number of memory slots 4
Base memory 8GB (2 x 4GB DIMMs)
Maximum memory 64GB (4 x 16GB DIMMs)
Use Small Outline Dual Inline Memory Modules (SO-DIMM) that meet all of these criteria:

• PC4-2400
• Unbuffered
• Nonparity
• 260-pin
• 2400MHz DDR4 SDRAM

Further down the page is the installation instructions which clearly show the memory access door that all 27" iMacs have had.

 

[Brookzy]

Specs are still wrong though. Should read PC4-19200.

I filed a bug report and the page was revised but still wrong.

 

[macduke]

Specs are still wrong though. Should read PC4-19200.

I filed a bug report and the page was revised but still wrong.

So is this what we need? https://www.amazon.com/Crucial-PC4-19200-SODIMM-260-Pin-CT8G4SFS824A/dp/B01BIWKP58/

I'm upgrading my machine at work and figured I could just get the 16GB config and add a couple of these.

 

[Swissness]

http://uk.crucial.com/ScanListView?modelTypeDisplay=&msg=compatible-upgrade-for&urlRequestType=Base&catalogId=10153&urlLangId=&manuFacturer=Apple&langId=-1&productLine=iMacSystems&mdlName=iMac(Retina5K,27-inch,2017)&storeId=10153&modelCatId=2099009

MacDuke, I have read that it's a good idea to buy mac-specific ram but I don't know for sure.

 

[MSastre]

I always upgrade all my Macs with Crucial ram.

 

[nambuccaheadsau]

Here are OWC's specs and prices:-


https://eshop.macsales.com/item/OWC/2400DDR4S4GB/

 

[theluggage]

Since there is a fair bit of confusion and misinformation (from Apple Chat discussions) about the new mid-2017 iMac 5K, here is Apple's updated Support Document for memory upgrades:

Specs are still wrong though. Should read PC4-19200.

So, the 8GB model comes with 2x4GB and 2 free slots...
Anybody know what configuration you get with the 16GB BTO? 2x8GB (yay!) or 4x4GB (boo!)?

 

[KnoeSS]

So, the 8GB model comes with 2x4GB and 2 free slots...
Anybody know what configuration you get with the 16GB BTO? 2x8GB (yay!) or 4x4GB (boo!)?

2 x 8. It was stated somewhere in a different topic with a screenshot of the order confirmation.