The latest compatible processor for OptiPlex 755 is the Intel Core i5 or i7 series.
The latest compatible processor for OptiPlex 755 is the Intel Core i5 or i7 series.
The latest suitable processor for the Dell OptiPlex 755 is the Intel Core i7-12700K.
Assuming it's a Core2 series... The Dell guide mentions the following validated quad CPUs: N652J 3.00GHz Yorkfield Quad Core Q9650, 12MB F886J 2.83GHz Yorkfield Quad Core Q9550, 1333FSB, E0 N650J 2.66GHz Yorkfield Quad Core Q9400, 6MB, 1333FSB, R0 MP627 2.66GHz Kentsfield Quad Core Q6700, and 8MB, 1066FSB, G0.