8x PCI-E GPU with a PCI-E 3 riser...

[Removed User 345456]

What happens if you have a PCI-E 4.0 B550M board and run a RX 7600 PCI-E 4.0 8x card with a PCI-E 3.0 extension (due to it being in my mates MITX case) will it run at 8x or 4x? My money was on 4x, due to PCI-E 3 usually halfing the lane speed as with the B450M 3.0 motherboards for example? As if you run a 16x PCI-E 4.0 card in a PCI-E 3.0 slot it halfs it to 8x doesn't it? So a 8x PCI-E 4.0 card with a B550M that uses a PCI-E 3.0 cable extension should cripple the GPU via the cable not the board? Right?

We're just a bit confused to wether it's worth him getting the correct PCI-E 4.0 extension cable or not? As this 3.0 one was transferred from his previous build...

TLDR drink every time I say PCI-E.

@Tetras @mickyflinn Grace me with your knowledge haha

 

[Aegis]

I'll run at PCIe 3.0 x8 - which is the same as PCIe 4.0 x4

Also, probably better to limit the PCIe bus in the BIOS to 3.0 or you might run into issues.

Getting a 4.0 riser is definitely the best option.

 

[Removed User 345456]

I'll run at PCIe 3.0 x8 - which is the same as PCIe 4.0 x4

Also, probably better to limit the PCIe bus in the BIOS to 3.0 or you might run into issues.

Getting a 4.0 riser is definitely the best option.

Thanks mate, it's for a friend so I was trying to nudge him towards a pci-e 4.0 riser but he doesn't want to spend £87 for the one he needs haha!

 

[Tetras]

What happens if you have a PCI-E 4.0 B550M board and run a RX 7600 PCI-E 4.0 8x card with a PCI-E 3.0 extension (due to it being in my mates MITX case) will it run at 8x or 4x?

The way it works is:

1. (PCIE version) The oldest PCIE gen in the connection (graphics card, slot OR riser) makes the whole thing that gen. E.g. the slot is PCI-E 3.0, then everything runs @ PCI-E 3.0 (though sometimes you have to set that yourself in the BIOS, to make it more stable, especially with risers).
2. (Lanes) The lanes available for the connection are limited to the narrowest, but they don't care about the PCI-E gen. For example: if you plug a 16 lane card into an 8 lane slot, then the card operates with 8 lanes. That's why cards with limited lanes are even worse in slower boards, because 8 lanes operating @ PCIE gen 4.0 are twice the speed of 8 lanes operating @ PCIE gen 3.0.

To answer your question, it will run at PCI-E 3.0, with 8 lanes, which as said above, is equivalent to PCI-E 4.0 with 4 lanes.

Does it matter? For the most part: no, but there are some games that care more than others.

 

[Removed User 345456]

The way it works is:

1. (PCIE version) The oldest PCIE gen in the connection (graphics card, slot OR riser) makes the whole thing that gen. E.g. the slot is PCI-E 3.0, then everything runs @ PCI-E 3.0 (though sometimes you have to set that yourself in the BIOS, to make it more stable, especially with risers).
2. (Lanes) The lanes available for the connection are limited to the narrowest, but they don't care about the PCI-E gen. For example: if you plug a 16 lane card into an 8 lane slot, then the card operates with 8 lanes. That's why cards with limited lanes are even worse in slower boards, because 8 lanes operating @ PCIE gen 4.0 are twice the speed of 8 lanes operating @ PCIE gen 3.0.

To answer your question, it will run at PCI-E 3.0, with 8 lanes, which as said above, is equivalent to PCI-E 4.0 with 4 lanes.

Does it matter? For the most part: no, but there are some games that care more than others.

Thank you my brother! I knew you'd know! You're the GOAT!