I had 2x4GB stick of Corsair left over from a Dell shell that I utilized for another build, confirmed working, and I decided to put it in my workplace workstation. The office desktop is a Optiplex 7010, my boss bought it around eight years ago, it came with 4GB Crucial, I added another stick of 4GB Hynix three years later. When I went to add the Corsair to bring it up to 16GB, it won't boot. I tried reseating the sticks, with the Corsair in 1 and 3 instead of 2 and 4, same effect. If I take the Corsair out, and leave in the original sticks, it boots fine. If I take out the original sticks, and leave in the Corsair, it boots fine. But why would there be an issue?