The 'X' Factor: PCI-Express Lanes
PCI-Express is designed to eventually replace both PCI and AGP. At first glance, this seems like a tall order. PCI in its 32-bit/33MHz desktop form transfers data at 133MBps, while the latest AGP 8x design transfers data at 2,133MBps. How can a single bus design be used to replace both types of expansion slots?
The answer lies in the modular nature of the PCI-Express design. PCI-Express uses a full-duplex (sends/receives data simultaneously) design. Each signal pair is referred to as a "lane", and each lane has a throughput of 250MBps (almost twice the throughput of PCI). In PCI-Express nomenclature, each lane is referred to as 'x'. By combining multiple lanes into a single expansion slot, PCI-Express can be used in place of both PCI and AGP slots.