[masraum]

Interesting
https://9to5mac.com/2019/04/05/how-to-upgrade-27-inch-5k-imac-2019-128-gb-ram-video-tutorial/

Apple’s long-awaited refresh of the iMac lineup finally happened, and it brought about incremental, but nonetheless worthwhile, enhancements to the lineup. Along with new 6-core and 8-core Intel options for faster CPU performance, new Radeon Pro Vega GPUs provide faster graphics.

In addition to the CPU and GPU, there’s another key upgrade element that got some love this year: Memory, and lots of it. For the first time, it’s now possible to upgrade the 27-inch 5K iMac with 128GB of RAM, although you’ll need to do so using third-party memory suppliers.

The good news is that even if you’re not interested in maxing out to 128GB of RAM, it’s incredibly easy to upgrade your 5K iMac’s memory, and you can save a whole lot of money in the process of doing so. Watch our video tutorial for a step-by-step 5K iMac memory upgrade guide.

Although the 2019 iMac can support up to 128GB of RAM, Apple restricts its build-to-order configurations to a maximum of 64GB of RAM. In fact, Apple notes that the machine supports a maximum of 64GB of RAM in a 4 x 16GB SO-DIMM module configuration, but it turns out that users wishing to upgrade can go beyond that number.

As initially discovered by OWC, the 2019 27-inch 5K iMac can support up to 128GB of RAM via a 4 x 32GB SO-DIMM module configuration. Hence, if you wish to upgrade your RAM, you’ll want to configure your iMac with the base 8GB amount, and buy compatible aftermarket RAM modules. OWC sells several RAM upgrade options for the 2019 5K iMac, and it was willing to send me a 128GB sample to test on video.

128GB RAM from OWC is only $650. I won't go that crazy, but I might do 64GB for $280.

Doing my own RAM upgrade saves a bundle.