Chosen Solution
Hello all I have a question about an Apple iMac 27” “Core i7” 4.0 (5K, Late 2015). https://everymac.com/systems/apple/imac/… It currently has 2 x 8GB sticks of (204 pin) 1867Mhz DDR3 RAM installed. The Everymac website doesn’t state what other RAM will work in this machine. Can anyone confirm if DDR3 (204 pin) 1600Mhz clock speed will work in this machine? I presume if it does i.e mix and match the 1600Mhz and the 1867Mhz together the logic board will clock the 1867Mhz to match the 1600Mhz? Any way of finding out the iMacs logic board memory clock speed settings or parameters? Any confirmation of this would be grateful. Thanks in advance
Using slower OS-DIMMs while possible will hold your system back. I strongly recommend sticking with what Apple recommends. The cost difference is not enough to fight over. Many people often get the next higher speed SO-DIMM’s if they can’t get the correct SO-DIMM’s. Mixing different speed OS-DIMMs can make a system unstable. While the bus clock will be at the slower speed, there is other aspects of the RAM that are not visible which can cause issues. Here’s a deeper look Memory (RAM) Timings & Latency: CAS, RAS, tCL, tRCD, tRP, tRAS Check your RAM configuration by opening: About This Mac > System Report > Memory Your RAM should be running all at the same speed bus speed.
