Question Pcix16 vs x8/x8

[Jass1989]

I'm attempting to rebuild my setup, trying to wrap my head around the pci situation. As I understand it. When you have dual PCI slots the bus will split the speed in some cases, cheaper chipsets. But when reading the specs on newegg, it gets a bit confusing.

I am attempting to replace CPU Mobo and ram.
Currently I have
2080ti pcie x16
PCI m.2 pcie x4
Pci m.2 pcie x4

I9-9900k

The specs on the board I am looking at as an example (while writing this I understand the manual says i7 but it's in a bundle on newegg with i9)

Asus prime z390
Intel® Socket 1151 for Intel® Core™ 9000 series, 8th Generation
Core™ i7 / i5 / i3, Pentium® and Celeron® processors
2 x PCIe 3.0/2.0 x16 slots (supports x16, x8/x8, x8/x4+x4,
x8+x4+x4/x0)
Intel® Z390 Chipset
3 x PCI Express 3.0/2.0 x1 slots
- PCIEX16_1 slot supports up to 3 Intel® PCIe NVME SSDs via a
Hyper M.2 X16 series Card.
- PCIEX16_2 slot supports up to 2 Intel® PCIe NVME SSDs via a
Hyper M.2 X16 series Card*
1 x PCIe 3.0 x16 slot (max. at x4 mode)

In my understanding the bottom pcix16 slot is x4 so good for an m.2
The top two slots are x16 but.... If I have a device is each one, it's throttled to x8? I wanted to put my x16 GPU and x4 m.2 in the top two. But from the sounds of it, my GPU would be throttled.

I would search for thing. But the keywords I am typing are not getting me the answers I an seeking. Someone has to point me in the correct direction, please?

 

[TJ Hooker]

That board has two M.2 slots. You don't need to use any of the PCIe slots for your SSDs, so the x16 slot would run at full bandwidth.

 

[Jass1989]

I understand that, but that doesn't answer the question. The question is is if I put something in both PCI slots, will it throttle the slots? Or will it both be at x16

That board has two M.2 slots. You don't need to use any of the PCIe slots for your SSDs, so the x16 slot would run at full bandwidth.

16?

 

[TJ Hooker]

Yes, putting anything into the 2nd x16 slot will limit the bandwidth of the 1st two x16 slots to x8/x8.