I have a mid 2010 13in MacBook Pro (7,1) with a 2.4GHz Intel Core 2 Duo processor running OS X 10.11.3 (El Capitan). I had 4GB of RAM (2x2GB) and I read somewhere that despite Apple's stated max of 8GB RAM (2x4GB) it will actually support 16GB (2x8GB) of RAM. So I bought Crucial RAM 16GB.
I installed both sticks in both slots and booted up, but the screen stays black and no chime. The sleep light on the front stays on (no blinking) but nothing happens after several minutes.
So I tried it with one of the new 8GB sticks and one of the old 2GB sticks and that works. Boots, starts, shows 10GB RAM (8 and 2) in the profiler.
Supposing it might be that one of the new sticks was bad, I tried every permutation of old with new and both 8GB sticks are good.
I read something about the firmware possibly being an issue, but I checked and I have the latest firmware according to this: https://support.apple.com/en-us/HT201518
Any ideas on how to get both sticks of 8GB to work together for a total of 16?
Also, if I can't get both to work, are there any reasons why I shouldn't do on of the old 2GBs and one of the new 8GBs together for 10GB?