Computer Components

Pci Express

PCI Express – What's Happening & Why Do I Care?

It's pretty clear to me that given the number of PCI Express plug-in cards available on the market today that PCI Express has won the high-bandwidth, serial interconnect wars of a few years ago.  No doubt, there are specific application niches were InfiniBand, RapidIO or HyperTransport work the best.  However, given the ever-expanding volume and types of PCI Express COTS boards available, you have to admit that PCI Express is the clear victor.  Maybe you disagree, but next time you're searching on-line or in your local Fry's for a plug-in board let me know how many non-PCI Express high-bandwidth, serial interconnect boards you manage to find.  I'm guessing that the number will be very small.

That brings us to a discussion on all the flavors of PCI Express that are now popping up. Does it matter that the interface is PCI Express version 1.1, 2.0, 2.1 or even the latest and greatest 3.0?  From the strictly, "Will the cards work?" standpoint the answer is "Yes", because the basic interconnect functionality is not affected by the PCIe version.  The PCI-SIG (Peripheral Component Interconnect Special Interest Group) did a smart thing when PCI Express 1.1 was first developed because they built the basic PCIe interconnect in such a manner as to ensure both scalability and backwards compatibility.  This critical specification feature enables the computer hardware to operate fine with just about any PCI Express card regardless of the board's interface version.  So, if that's the case why do I care about the various types of PCI Express interfaces?

Increased system performance is the primary reason you care about the specific PCI Express interface.  A PCI Express 2.0 COTS board installed in an industrial computer will send its data over to the system host board (SHB) twice as fast as older PCI Express 1.1 boards.  Of course, this assumes that the systems' SHB has PCIe 2.0 interfaces.  The same scenario plays out in an embedded motherboard.  If the motherboard is equipped with PCIe 2.0 card slots then any PCIe 2.0 card placed into one of these slots will send it's data to the board's CPUs twice as fast as in a PCIe 1.1 system.  This speed advantage is cumulative and can be critical in high-performance computing applications. 

PCIe 2.1 uses many of the interface architecture improvements developed for PCIe 3.0, but communicates at the same interface speeds used in PCIe 2.0.  PCIe 3.0 achieves twice the communication speeds of PCIe 2.0 through various architecture and protocol management improvements.  PCIe 3.0 silicon will start becoming readily available in 2011.

Further information can be found at Trenton Technology or the Trenton Blog.

About the Author

Jim Renehan is the Director of Marketing for Trenton Technology. Jim has held various marketing and application engineering positions in the embedded computing, industrial automation, and automatic identification industries. Jim holds a BS in Industrial Technology from Iowa State University of Science and Technology in Ames, Iowa.  For further information, please visit Trenton Technology.

What is the difference between PCI bus and PCI Express?

I'm getting a new graphics card but i wondered what these terms meant. If i have a PCI bus but the graphics card says PCI Express, can i run it?

To directly answer your question: No, you definately need a PCI-E x16 slot to install a PCI-E x16 videocard. If you have a PCI-slot buy a PCI legacy card or a new computer.

Modern internal videocards mostly come with a PCI-E x16 2.0 or 2.1 interface-connector for connection to the motherboard.

Personally im not sure if a PCI-E x16 2.1 videocard would work in an version 2.0 slot on the motherboard, might very wel work, but a version 2.0 videocard should be compatible with a version 1.x slot on the motherboard. So if i had a version 1.x PCI-E x16 slot i would buy a version 2.0 videocard, but if 1 had a version 2.1 interfaceslot i'd go for a version 2.1 videocard just to be on the safe side, although a version 2.0 videocard might also work, not sure.

example of a pci 2.0 card:

http://www.tigerdirect.com/applications/SearchTools/item-details.asp?EdpNo=6976278&CatId=3669

(use with a PCI-E x16 version 2.0 or 1.x interfaceslot on the motherboard)

example of a pci 2.1 card:

http://www.newegg.com/Product/Product.aspx?Item=N82E16814102932

example of a pci card:

http://www.newegg.com/Product/Product.aspx?Item=N82E16814139054

benchmark listing of videocards to compare performance:

http://www.videocardbenchmark.net/

Win 7 on OCZ Revo PCI Express x4 SSD Part 1 of 5 (for nOObs)