How does PCI-E lane division work?

[mwmorph]

I understand new Z77s have 16 lanes, but if I have a PCI-E 1x sound card and I want to go for SLI GTX670s, does that means I'll have 1 card run at 8x, 1 at 4x and the damn sound card run at 1x, bottlenecking my GTX670s?

Is the only way around this getting a PLX chip equipped motherboard?

 

[lopri]

Check the boards' manuals. There should be block diagrams showing how PCIe lanes are configured. If you want to reserve the PCIe lanes from CPU for video cards, you can use the PCIe lanes rooted in south bridge.

 

[ericloewe]

No, the sound card should run off the chipset's x4 2.0 lanes, while the GPUs run off the processor's x16 3.0 lanes

 

[mwmorph]

Ahh, thanks for the replies, I had no idea the chipset still had PCI-E lanes. I assumed all PCI-E was shifted to the CPU and a system had only 16 lanes total.

 

[lopri]

Of course the chipset still has PCIe lanes. That's how they communicate with the CPU as well! LGA1155/1156 CPUs actually have 22 (maybe 24, not sure exactly how many but more than 16) PCIe lanes, with 4 reserved for DMI.