Introduction

The NVIDIA GeForce RTX 5090, powered by the Blackwell architecture, sets a new benchmark in GPU technology—not just for performance. With its adoption of the PCI-Express 5.0 x16 interface, a first for a high-end graphics card, the RTX 5090 achieves an incredible 64 GB/s of bidirectional bandwidth, a dramatic improvement over the RTX 4090's PCIe 4.0 x16 bandwidth of 32 GB/s. This substantial leap can offer significant benefits for gaming, professional workloads, and data-intensive tasks, enabling smoother performance and faster data transfers.



While PCIe 5.0 unlocks the GPU's full potential, the RTX 5090 remains backward compatible with earlier PCIe generations, such as PCIe 4.0, 3.0, and even 2.0 and 1.1. This compatibility is invaluable for users with older systems, but it also prompts an essential question: how much does the PCIe interface impact performance?

In this article, we'll explore this by testing the RTX 5090 at different PCIe speed levels and bandwidths—from the latest PCIe 5.0 down to PCIe 1.0. By analyzing the GPU's performance across various scenarios, including gaming benchmarks at different resolutions, with RT disabled and enabled, we aim to determine the real-world impact of PCIe bandwidth on this next-generation graphics card.

From a technical perspective, PCI-Express 5.0 uses the same Non-Return-to-Zero (NRZ) signaling as PCIe 4.0 but implements stricter signal integrity measures to handle its doubled data rate of 32 GT/s per lane. Enhanced equalization techniques, like Decision Feedback Equalization (DFE), help counteract signal degradation and interference at these higher speeds. Additionally, tighter timing controls reduce jitter, ensuring reliable data transfer without the need for more complex signaling methods (like PAM3 or PAM4). These improvements allow PCIe 5.0 to achieve twice the bandwidth of PCIe 4.0 while maintaining compatibility with the same physical interface.

Our tests will help answer key questions for potential upgraders: is PCIe 5.0 essential to fully leverage the RTX 5090's power, or can older systems still deliver competitive performance with this cutting-edge GPU? What's the impact when an SSD eats half your PCIe lane budget? Can you run RTX 5090 in the bottom x16 slot at decent performance? Whether you're considering upgrading your system or simply curious about how much PCIe bandwidth influences modern GPUs, this analysis will provide detailed insights.

Read on as we dive into these performance tests and uncover how the NVIDIA GeForce RTX 5090 scales with various levels of PCI-Express bandwidth available.