Plx chip? Whas exactly does it do

[Andrew Storlie]

So i keep hearing stuff about "plx chip" that basicly allows a motherboard to run more lanes then the cpu has available or something like that. 

 

Can Linus to a tech quicky on plx chips?

 

Can someone here explain what there are and exactly how they work? 

[Glenwing]

14 minutes ago, Andrew Storlie said:

So i keep hearing stuff about "plx chip" that basicly allows a motherboard to run more lanes then the cpu has available or something like that. 

 

Can Linus to a tech quicky on plx chips?

 

Can someone here explain what there are and exactly how they work? 

 

The generic term is a PCI Express Switch; PLX is a company that makes these chips. The number of PCI Express lanes is limited by what the CPU provides, there is no way to get around that. A PCIe switch allows more slots on the motherboard to be wired with lanes, maybe with a 16-lane CPU, a switch would allow you to have 32 lanes active at the same time. However, the switch itself is only connected back to the CPU through the 16 lanes that the CPU provides. So the total amount of PCIe bandwidth isn't increased by a PCIe switch. But switches can be used to circumvent lane restrictions; for example NVIDIA SLI requires at least 8 lanes on each GPU for no reason, and a PCIe switch can be used to fool 3 or 4 GPUs into thinking they're all running on x8 slots, even though only 16 lanes are available in total.