Third PCIe slot on Z77 motherboards only works with Ivy Bridge

Posted on Tuesday, April 10 2012 @ 22:06 CEST by Thomas De Maesschalck
TechPowerUp reports the third x16 slot on high-end Z77 motherboards only works with an Ivy Bridge processor installed. Users with a Sandy Bridge processor will be unable to use three graphics cards.
This can be explained by taking a close look at the block diagram of Intel Z77 Express system. Z77, in combination with "Ivy Bridge" processors, allows the CPU root complex to drive three devices. Its single PCI-Express x16 link can be arranged in three ways: x16/NC/NC; x8/x8/NC; and x8/x4/x4. As you can see, the third long slot is taken into the configuration. Intel figured out that since PCI-Express 3.0 x4 offers bandwidth comparable to PCI-Express 1.0 x16 to gen 3-compliant graphics cards, it's wise if the third electrical x4 slot is also wired to the CPU's PCIe root complex. This renders most high-end LGA1155 motherboards with such CPU-driven third x16 (x4) slots 3-way SLI/CrossFireX-capable. Sweet.


About the Author

Thomas De Maesschalck

Thomas has been messing with computer since early childhood and firmly believes the Internet is the best thing since sliced bread. Enjoys playing with new tech, is fascinated by science, and passionate about financial markets. When not behind a computer, he can be found with running shoes on or lifting heavy weights in the weight room.



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