PCIe发展史：从插槽到NVMe再到CXL

## PCIe Speed Progression

| Generation | Year | Per-Lane Speed | x16 Total |
|---|---|---|---|
| PCIe 1.0 | 2003 | 250 MB/s | 4 GB/s |
| PCIe 2.0 | 2007 | 500 MB/s | 8 GB/s |
| PCIe 3.0 | 2010 | ~1 GB/s | 16 GB/s |
| PCIe 4.0 | 2017 | ~2 GB/s | 32 GB/s |
| PCIe 5.0 | 2019 | ~4 GB/s | 64 GB/s |
| PCIe 6.0 | 2022 | ~8 GB/s | 128 GB/s |

## Why PCIe Matters for Cables

PCIe isn't just an internal slot — it's the foundation for:
- **Thunderbolt** (PCIe tunneled over USB-C)
- **NVMe SSDs** (PCIe x4 for storage)
- **External GPUs** (PCIe over Thunderbolt)
- **M.2 connectors** (PCIe physical interface)

## NVMe Speed by PCIe Gen

- PCIe 3.0 x4 NVMe: ~3.5 GB/s (Samsung 970 EVO)
- PCIe 4.0 x4 NVMe: ~7 GB/s (Samsung 980 PRO)
- PCIe 5.0 x4 NVMe: ~12 GB/s (Samsung 990 EVO Plus)