The PCI-Express interconnect is the dominant interconnection technology within a single computer node that is used for connecting off-chip devices such as network interface cards (NICs) and GPUs to the processor chip. The PCI-Express bandwidth and latency are often the bottleneck in the processor, memory and device interactions and impacts the overall performance of the connected devices. Architecture simulators often focus on modeling the performance of processor and memory and lack a performance model for the I/O devices and interconnections. In this work, we implement a flexible and detailed model for the PCI-Express interconnect in a widely known architecture simulator. We also implement a PCI-Express device model that is configured by a PCI-Express device driver. We validate our PCI-Express interconnect performance against a physical Gen 2 PCI-Express link. Our evaluation results show that the PCI-Express model bandwidth is within 19.0% of the physical setup. We use our model to evaluate different PCI-Express link widths and latency and show its impact on the overall I/O performance of an I/O intensive application.