The original PC came w/only 4G total.
I Just purchased two Mushkin 8G DDR3s for my Optiplex 790, see attached photo.

The PC uppon power up it beeps once, then short pause and beeps 3 more times, then pause and two more times, then shuts off.

As my research shows, this is a memory error, "DIMMs not being properly identified or used".

I since then, I removed CMOS battery, unplugged PC, held power down for 30+ seconds, put all back, still same.

I put back the original memory, all is well!

Any ideas? Aren't these compatible? As per my research, I can have up to 16G.

Thank you in advance for ANY help!