Late 2010 Core i7 iMac Shutdown

I've had this same problem and I'm happy to report I've got it licked!

The key is you MUST have Samsung RAM in the "Top" two slots. The Top slots being the ones closest to the screen. I have iRAM in the other two slots and have been running 16GB happily for the last 6 months without ANY issues.

It took some digging to find out that Apple has paired slots again like the good ole' days. Just put 8GB of Samsung ram in the top slots and your other RAM should be fine in the bottom slots (towards the back of the iMac.)

Hope this helps.

After upgrading to Lion, the frequency of my shutdowns increased, so I removed one of the four 4GB sticks. I have had no problems since.

I notice that OWC is offering 8GB sticks for the late July 2010 iMac, though the price is quite steep. I shall wait for it to come down, and then possibly upgrade to 32GB. I hope that by then there will be no problems with such an upgrade.

Sam here, Mid Summer 2010 imac 27", 16 GB RAM, randomly sudden shutdowns. Brought the machina to the local Apple Provider. They found no problem, so i paid the bill and returned the mac to the office.

Next thing will be removing one of the 4 RAMs..

Crossing fingers.

I've noticed how the switch off is associated with the sudden overload of the processor. I was doing number cruching for a science project. When loading files to be processed in sequence nothing would happen. The i7 iMac could handle 8 such files (1 per core) all at once running at near 100% for days on end. But when I paused the process and then later got it going again it immediately switched off. It can't handle going from idle to max power all at once. That's the problem. It's a design flaw by apple.

Since I have such a machine I want to know if you guys have run your machines with more than 8GB after removing the memory. Was the cpu running on hyperthreatting or not. Where you running the same load after taking out or replacing the Ram with Samsung Ram ?