There are several types of PCIe Root Complexes, including:

To address these challenges, researchers and developers are exploring new technologies, such as:

Modern root complexes (e.g., in Intel Core 12th–14th gen or AMD Ryzen) provide dedicated lanes (x16 for GPU, x4 for NVMe) directly to the CPU. This reduces contention and delivers near-theoretical PCIe 4.0/5.0 speeds.

Modern CPUs often have "dedicated" PCIe lanes (typically 16 or 20) that go straight to the primary GPU and M.2 slots, managed by the on-chip Root Complex. Summary 💡

Data doesn't have to travel across long motherboard traces to reach the CPU.