|Sun System Handbook - ISO 3.4 June 2011 Internal/Partner Edition
Solution Type Technical Instruction Sure
Solution 1003507.1 : Sun Fire[TM] Servers: Differences Between PCI-X and PCI Express I/O Technologies
This document discusses the differences between PCI-X and PCI Express I/O
technologies. Sun currently ships PCI and PCI-X based systems and, in the
near future, will be shipping PCI Express based systems.
Steps to Follow
PCI, PCI-X and PCI Express are industry-standard I/O technologies.
PCI supports 33MHz, 66MHz clock speeds and operates in 64/32bit mode. PCI supports 5V as well as 3.3 volt signaling. PCI-X supports 66MHz, 133MHz, 266MHz, and 533MHz clock speeds and is 64-bits wide. PCI-X 66MHz, 133MHz, 266MHz and 533MHz clock speeds provide the following throughput respectively: 4Gbit/sec, 8Gbit/sec, 17Gbit/sec, 34Gbit/sec. PCI-X cards are backward compatible to the "old regular" PCI-based systems. PCI-X supports only 3.3 volt signaling. Due to this, PCI-X adapter cards are only backward compatible with previous generation 3.3V PCI systems. PCI Express is a serial interconnect, point-to-point link, not a parallel multidrop bus as is PCI/PCI-X. PCI Express can run on many lanes: x1,x2, x4,x8, and x16. Each lane gives 250Mbit/sec in single direction and 500Mbit/sec in duplex mode. The x16 lane gives 16Gbyte/sec(128Gbit/sec) throughput. PCI express is similar to Infiniband; they both have serial interconnects and can be used for interconnecting servers and clustering. PCI-X is a shared bus. For example, all the devices on the bus share a single set of data lines and signal lines. PCI-Express is a switched bus, which should allow much more efficient use of the bandwidth between the devices and the system bus. Physically, PCI-X and PCI Express are very different. PCI Express requires a different hardware connection, causing old PCI cards not to work in PCI Express slots. But from software perspective or from a driver/writers perspective they are identical, which is what makes PCI Express so attractive. This allows companies to re-use the PCI-X/PCI software for PCI Express.
Sun Fire E25K Server
Sun Fire E20K Server
Sun Fire 15K Server
Sun Fire 12K Server
Audited/updated 12/03/09 [email protected], Entry Level SPARC Content Team Member
PCI, PCI-X, PCI Express
Previously Published As
User Name: C149439
Comment: Added product trademark. Corrected measurement abbreviations. Edited text.
User Name: C149439
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