iMac 2012 27¨ upgrade RAM

[DavidJezek]

Good day,
i bought iMac 27 2012 with 8GB RAM. So I decided to add another 8GB and here's the problem. I have 2x 4GB original and 2x 4GB purchased. And when all four memories are installed, only 3 beeps sound. Interestingly, any combination of cards in the bottom two slots works (2x original, 2x purchased, 1 and 1), but as soon as I add a card to the 3rd or 4th slot, the iMac won't turn on and it doesn't matter what memory is there. Tried resetting the NVRAM, cleaning the ports with compressed air, still nothing. So I wanted to ask if anyone could think of anything.
Thank you

 

[Nguyen Duc Hieu]

Good day,
i bought iMac 27 2012 with 8GB RAM. So I decided to add another 8GB and here's the problem. I have 2x 4GB original and 2x 4GB purchased. And when all four memories are installed, only 3 beeps sound. Interestingly, any combination of cards in the bottom two slots works (2x original, 2x purchased, 1 and 1), but as soon as I add a card to the 3rd or 4th slot, the iMac won't turn on and it doesn't matter what memory is there. Tried resetting the NVRAM, cleaning the ports with compressed air, still nothing. So I wanted to ask if anyone could think of anything.
Thank you

Maybe it's new to you, but malfunctioning RAM slots is not a very rare incident in the world of personal computers.

 

[rpmurray]

Some of the later iMacs are very picky about RAM and won't work well together unless they're from the same manufacturer. Are you sure that all four have the exact same specs?

Power-On Self-Test (POST)

• Intel-based Mac computers such as the iMac rely on a combination of tones and blinking LED lights to display Power-On Self-Test (POST) error codes.
• If the computer detects out-of-specification or no Random-Access Memory (RAM), the screen will remain black but the computer will beep. This error condition may be due to physically damaged RAM, installing an incorrect type of RAM, or not having RAM installed.
• Some RAM may appear to pass POST, but still cannot be used by the operating system. In this case, the computer will display a gray screen, sound three beeps and repeat beeps until computer is turned off.
• The solution to both of these situations is to first reseat RAM and test computer again. If RAM fails POST again, remove all installed RAM and test by installing one by one each RAM module that has been verified to work correctly on another computer (“known-good” RAM, for example) or order new RAM.
• A sequence of tones heard at startup or a no video symptom may also be fixed by temporarily removing/replacing the backup battery.

If your Mac beeps during startup

 

[DavidJezek]

Yes, the parameters are identical. Even one old and one new work together without problem in slot 1 and 2. It will probably be non-functioning slots, because even if I put the original ram in slots 3 or 4, the iMac will not start.

 

[Fishrrman]

Have you tried "alternating" the RAM DIMMs?

In other words:
Slot 1 - original RAM DIMM
Slot 2 - new DIMM
Slot 3 - original DIMM
Slot 4 - new DIMM