Hello, I have upgrade my iMac 5k 27 inch to 32 GB. Carefully chosen, the Other World Computing DDR3 1867 MHz was used. Actually, since I change the RAMs, iMac work and doing well EXCEPT some time it hangout and the restart spontaneously!!
iPad (3rd gen) Wi-Fi + Cellular, iOS 5.1.1
Do the Reset SMC procedure. For an Intel iMac, this is basically unplugging the Mac's power cord and reconnecting, following a specific procedure
Reset the System Management Controller (SMC) on your Mac - Apple Support
Also, look at how the iMac is connected to power. If it is on a power strip (surge suppressor) along many other peripherals, such as the power supplies for external drives and other devices, a printer, a speaker system, your desk lamp... Try connecting the iMac to its own power outlet, by itself (or with a small number of other things).
Thank you for rapid response. I am gonna try such thing and see
Sounds like maybe have a loose or partially seated module.
I would recheck to ensure that all of the modules are firmly seated in the slots.
Install memory in an iMac - Apple Support
Then if that does not help, contact OWC support and have them help you with troubleshooting and/or replacement module(s).
ram changed then the iMac 5K start restart multiple time
