When making highly sensitive measurements on high-speed digital boards, there is little room for error. Rambus® memory architecture produces extremely fast signals (250-picosecond risetime) on computer mother- boards and memory boards and thus requires special measurement tools. The challenge is even greater for the digital design engineer when faced with Rambus traces that are only 1-2” in physical length. Smaller form factor printed circuit boards for new laptop applications and mother- boards are creating a need for more precise measurement techniques. By using a test procedure called Time Domain Reflectometry (TDR) normal- ization, high-speed oscilloscopes can accurately measure the character- istic impedance of these short traces by removing sources of error. This application note will describe the test equipment and general method- ology that is recommended to make these signal integrity measurements.