Maintaining microprocessor compatibility across process generations

This paper presents two approaches that have been used to maintain socket compatibility between a pair of microprocessors operating at different supply voltages. A current balancing scheme to keep independent regulators within their specified operating range when shorted through the microprocessor socket is presented. Using a network of termination resistors in the microprocessor's package, an operating scheme was developed such that minimum regulation current requirements could be met and a balanced current environment could be achieved inside two different switching regulators operating at different frequencies. The design and the implementation details of the current balancing method in the microprocessor is described and compared with measured data.