Hello,
Optiplex 790 has a Intel Q65 Express Chipset and supports Sandy Bridge (2nd Generation i3, 2nd Generation i5 and 2nd Generation i7). The system was tested and shipped with 2 kinds of i7 processors.
1. Intel Core i7 2600 / 3.40GHz.
2. Intel Core i7 2600S / 2.80GHz.
According to the system specification, I would like to say that the system should be compatible with Intel Core i7-2700K Sandy Bridge 3.5GHz (3.9GHzTurbo) LGA 1155 95W Quad-Core Desktop Processor Intel HD Graphics 3000.
Please write back if you have any further queries.