Series-stacked server power delivery architectures have been proposed recently that can achieve much higher energy efficiency than conventional power delivery architectures. When servers are connected in series, differential power processing (DPP) converters can be used to regulate the server voltages when the servers are consuming different amount of currents. Server-to-bus DPP architecture has unique advantages among several other DPP architectures such as being able to achieve the minimum power processed in the DPP converters, and having a higher reliability than other DPP architectures. This work presents the development of a server-to-bus DPP architecture for server power delivery. The hardware prototype is built with four 4-to-1 isolated DPP converters with GaN switches. Four 12V 120W Dell servers are used in the bench test to validate the operation of server-to-bus DPP. 98.99% efficiency is achieved while the servers are running a real-life data center computational load.