There is a relation to the GPU with the processor, but in processing load, there isn't any significant dependence (as you put it).
A CPU has a specific set of PCIe lanes that can be used to have information sent along it - the GPU tends to use 16 of these lanes although they can work on fewer lanes (such as 8 lanes) (this does not affect the final performance of the processor).
It really depends on a motherboard and the CPU, though. Some motherboards can provide a total number of lanes and can split them accordingly while limited by the maximum capacity of a CPU.
ingtar33 :
the cpu sets the max.
the motherboard sets how they're used. you can tell how many pci-e lanes are used at each pci-e access point by the x16/x8/x4/x1 after it. The number tells you the max number of lanes that point will take.
So if you have a cpu with 24 pci-e lanes max and a motherboard with 3 pci-e 3.0x16 connections, you know that only 1 of those will run in full pci-e3.0x16 with that cpu.
(https://goo.gl/2C8zp4)