3-way SLi with Only 16 PCIe Lanes?

How to extend the number of PCIe lanes available from your CPU using PLX

Steve Smith talks about PLX, a technology that extends the number of usable PCIe lanes.

Episode #6-06 released on October 11, 2015

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A mainboard has a set limit of PCIe lanes, as I have talked about before, consumer boards currently have 16 to 20 PCIe lanes available from the processor, but what if you needed more?

The feature is PLX, and what is does is amazing when you want a third GPU, or more hardware than your processor would normally support. Your mainboard would typically only be able to connect devices with connections up to 16 to 20 PCIe lanes, unless your using a X99-3 Processor, or similar. This means that consumer mainboards would only be able to connect 2 GPU cards from Nvidia in SLi at any given time, but wait a minute, aren't there mainboards that claim higher on the same consumer platforms?

The answer is yes, there are other mainboards that can for some reason connect more than 2 graphics cards under SLi, and they use PLX to be able to achieve this, by multiplexing the PCIe lanes. This can double the available number of PCIe lanes available to the mainboard, while using a CPU that has fewer than needed PCIe connections built within.

However, this feature can only be found on a small set of mainboards available to the general public, so what are you supposed to do?

Well, if you are anything like me, you like to upgrade and maintain your computer, you have some expectation that you will be keeping your tower for a relatively long time, and you may add more cards, so if you are the type to upgrade with new technology, then the answer is easy. Buy a mainboard that supports PLX now, that way you can always upgrade in the future. Now, these mainboards can be upwards of three hundred dollars, or more, so only people who do a lot of upgrading should be buying a mainboard of this price, and only to avoid having to replace the mainboard in the future.

Wondering how PLX works, exactly, well apparently that is kept secret, but we could always guess that because it multiplexes the PCIe lanes to imitate double the lanes, that it acts like a telephone switching system, which introduces some processing overhead, but the increase bandwidth available to all the hardware will significantly compensate for the overhead.

Some mainboards from Asus that support include the Z97-PRO WIFI AC, and Z97-WS. There are mainboards some other manufactures, as well. To confirm if a mainboard has PLX support, you simply need to look at the specifications of the mainboard, more specifically for PLX, and multi GPU support beyond 2-way, and Quad SLi.

Host : Steve Smith | Music : Jonny Lee Hart | Editor : Steve Smith | Producer : Zed Axis Productions

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