Apple released a document for developers to assist them in building and modifying their Mac OS X applications to run as universal binaries that will run native on Mac computers with PowerPC or Intel processors.
This document is designed to help developers determine exactly how much work needs to be done and provides useful tips for general as well as specific code modification scenarios. It is intended to be used as a reference and not to be read cover to cover. It describes the prerequisites for building code as a universal binary and shows how to do so using Xcode. It also discusses the differences between the Intel and PowerPC architectures that can affect code behavior and provides guidelines for ensuring that your universal binary code builds correctly.