The compatibility of a processor is determined by the motherboard on your system due to the following:
Their testing requires the use of our processors (not vice-versa). The board must be validated for the power and thermal specifications of the processor. The system builder must release a BIOS update for the board with explicit support for the stepping and frequency of the processor. They should also provide any configuration changes or updates specific to the board.
Due to this, we recommend contacting Dell* and consult whether you have upgrade options or not, on your Dell* system.
Compatibility information between Intel(R) motherboards and processors can be found here: http://processormatch.intel.com/