This paper investigates Input/Output Buffer Information Specification Algorithmic Model Interface (IBIS-AMI) model extension for 25 Gb/s PAM4 (4-level Pulse Amplitude Modulation) serial link to improve the development efficiency. By using the ADS (Advanced Design System) Channel Simulator, the effects of device package, jitter and crosstalk on the actual performance are studied at first. Then, for forward error correction (FEC) technique, the bit error rate (BER) performance and the bathtub curves are analyzed in detail. Simulation results show that device package, jitter and crosstalk can make the link performance worse. And much better performance can be obtained by using the combination of equalization and FEC techniques compared with using the equalization technique separately.