1. 外围组件互连扩展(PCI-X)：
PCI-X 或外围组件互连扩展是与扩展卡一起提供的本地计算机总线。它是具有更高带宽的外围组件互连的扩展版本。它由IBM、HP、Compaq于1998年推出，具有支持更高时钟速度和热插拔的特点。它是并行设计的，宽度为64位。由于其运行缓慢，它后来被名为 PCI-E 的其他版本所取代。
2. 外围组件互连 Express (PCI-E)：
PCI-E 是 Intel、Dell HP 和 IBM 于 2003 年推出的外围组件互连扩展 (PCI-X) 的替代版本。 PCI express 是连接显卡、Wifi、硬盘和其他硬件设备的串行总线。它的工作速度比 PCI-X 快，输入和输出引脚数更少，因此比 PCI-X 工作得更好。这个版本比旧版本有很多功能。
PCI-X 和 PCI-E 的区别：
| S.NO | PCI-X | PCI-E |
|---|---|---|
| 1. | PCI-X is a computer bus that connects hardware devices and has an expansion card. | An advanced version of PCI bus that connects graphic ports, Wifi and other devices. |
| 2. | It was introduced in the year 1998 by IBM, HP and Compaq. | It was introduced in the year 2003 by Intel, Dell, HP and IBM. |
| 3. | It is a parallel bus interface | It is a serial bus interface. |
| 4. | PCI-X is the abbreviated name for Peripheral Component Interconnect eXtended. | PCI-E is the abbreviated name for PCI Express. |
| 5. | It works slower. | It works faster. |
| 6. | PCI-X provides a slower data rate | PCI Express provides faster data rate. |
| 7. | The PCI-X has longer slots | The PCI-E has shorter slots. |
| 8. | The speed of a PCI-X slot is upto 1064MB/s. | The speed of a PCI-E slot is upto 16 GB/s. |
| 9. | It has less features. | It has more features. |
| 10. | The width of PCI-X is about 64 bits. | The width of PCI-E is 1 per lane |