Difference Between PCI Express and PCI Express 2.0

PCI Express vs PCI Express 2.0

PCI Express usually refers to the PCI Express 1.1 specification, which was introduced by Intel in 2004 to meet the requirements of I/O platforms. However, it did not meet the bandwidth requirements of the enriched graphic-based applications. PCI Express 2.0 was launched in 2007 as an advancement to PCI Express 1.1, with all new functional enhancements. It also offered double the bandwidth when compared with PCI Express 1.1. Apart from this, the per-lane throughput of the PCI Express 2.0 was also doubled to 500MB/s, whereas, in case of PCI Express 1.1, it was only 250MB/s.

The slot format used by both PCI Express 1.1 and PCI Express 2.0 is the x16 PCIe slot. However, PCI Express 2.0 slots are subjected to sustain up to a maximum of 150 watts, and PCI Express 1.1 slots can sustain only 75 watts, which is exactly half of the PCIe 2.0 slot’s capability. Apart from this, the PCIe 2.0 standard enables slot power limits to change, in order to allow for the higher powered slots that support the latest high performance cards.

The greatest advantage of the PCI Express 2.0 standard is that it is fully backward compatible with the PCI Express 1.1. All the latest graphic cards designed for the latest version of PCI Express, i.e. PCIe 2.0, are completely backward compatible with the older motherboards of the PCI Express 1.x version, by utilizing its available bandwidth. The latest motherboards designed for the PCIe 2.0 version are also backward compatible with the older versions of PCI Express 1.x cards. Hence, the PCI Express 2.0 standard is inclusive of the PCI Express 1.x, and not vice versa.

The PCI Express 2.0 standard provides faster signaling than the previous PCI Express versions, thus doubling the bit rate from 2.5GT/s to 5GT/s. This proved useful for high bandwidth applications. Apart from this, the faster signaling feature in the PCIe 2.0 standard allows for a narrow configuration in terms of interconnect links, thus saving on costs. For example, the PCI Express 1.x uses 8 links at a maximum bit rate of 2.5GT/s to provide a total bandwidth of 4GBytes/s. The same bandwidth is achieved by the PCI Express 2.0 using just 4 links at a maximum bit rate of 5GT/s. Thus, the platform implementation cost is reduced while maintaining the same performance.

Summary:

1. PCI Express 1.1 was introduced to meet the requirements of I/O platforms, and did not support enriched graphics based applications, whereas PCI Express 2.0 supported both.

2. PCI Express 2.0 offered double the bandwidth when compared with PCI Express 1.1.

3. The per-lane throughput of the PCI Express 2.0 is 500MB/s, whereas it’s 250MB/s in the case of PCI Express 1.1.

4. PCI Express 2.0 slots can support 150 watts, while PCI Express 1.1 slots can sustain only 75 watts.

5. The PCI Express 2.0 standard enables slot power limits to change, whereas the PCI Express 1.x does not have this feature.

6. The PCI Express 2.0 standard is inclusive of all the PCI Express 1.x features, and not vice versa.

7. The PCI Express 2.0 standard provides faster signaling than the previous PCI Express versions.

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