PCIe lanes

[BiotechBen]

Hey, so I was wondering, is there like a ratio of some sort for like splitting PCIe 3.0 lanes to PCIe 2.0 lanes? So like would a PCIe 3.0 1x lane split into like 2 PCIe 2.0 1x lanes or something?

[Grabhanem]

8 minutes ago, BiotechBen said:

Hey, so I was wondering, is there like a ratio of some sort for like splitting PCIe 3.0 lanes to PCIe 2.0 lanes? So like would a PCIe 3.0 1x lane split into like 2 PCIe 2.0 1x lanes or something?

AFAIK each lane is about double the bandwidth of the next step down, so 1x 4.0 = 2x 3.0 = 4x 2.0 = 8x 1.0.

However, there isn't really a good practical way to split lanes-- the chips to do it exist, but they tend to be very expensive and niche.

[Windows7ge]

Grabhanem's explanation is solid. With each generation the bandwidth doubles. Hence many devices can run off PCI_e x8 Gen 3 without a bottleneck. Even more so with Gen 4 compatibility.

 

Now are you asking about running multiple devices off a single PCI_e slot?

[BiotechBen]

So like if your mobo is running 1x slots at 2.0, what does that convert to for 3.0 lanes if that makes sense?

[Kilrah]

Doesn't really make sense, no... Just that running the full bandwidth on that slot will use half of a 3.0 lane's bandwidth.

[BiotechBen]

Just now, Kilrah said:

Doesn't really make sense, no... Just that running the full bandwidth on that slot will use half of a 3.0 lane's bandwidth.

Okay, that's as close to the answer to the question I think is possible... So two 1x 2.0 lanes would use the bandwidth of one 3.0 1x lane

 

[Windows7ge]

16 minutes ago, BiotechBen said:

Okay, that's as close to the answer to the question I think is possible... So two 1x 2.0 lanes would use the bandwidth of one 3.0 1x lane

 

You got it. Is there something in particular that you're looking to do with this information or was it just curiosity? 

[BiotechBen]

22 minutes ago, Windows7ge said:

You got it. Is there something in particular that you're looking to do with this information or was it just curiosity? 

A ryzen 5 2600 with a ASRock b450 pro4 and rx480 with nvme drive. Wanna put a network card in but don't want to deactivate or steal lanes from things like the graphics card. It says that it has 4 PCIe 2.0 1x slots. Just wanted to check that running an nvme and graphics card and 1x network/bluetooth card aren't going to be a problem.

[-rascal-]

29 minutes ago, BiotechBen said:

A ryzen 5 2600 with a ASRock b450 pro4 and rx480 with nvme drive. Wanna put a network card in but don't want to deactivate or steal lanes from things like the graphics card. It says that it has 4 PCIe 2.0 1x slots. Just wanted to check that running an nvme and graphics card and 1x network/bluetooth card aren't going to be a problem.

 

The Ryzen 2600 provides 16 + 4 lanes.

16 goes to the top PCI-E X16 slot.

4 goes to the top M.2 NVMe slot, OR bottom PCI-E X16 slot.

 

The remaining PCI-E x1 slots, and second M.2 slot is provided through the B450 chipset on the motherboard.

 

In other words, you will be fine; won't be stealing from the graphics card and/or NVMe SSD by adding a PCI-E X1 network / bluetooth card.

[BiotechBen]

1 hour ago, -rascal- said:

 

The Ryzen 2600 provides 16 + 4 lanes.

16 goes to the top PCI-E X16 slot.

4 goes to the top M.2 NVMe slot, OR bottom PCI-E X16 slot.

 

The remaining PCI-E x1 slots, and second M.2 slot is provided through the B450 chipset on the motherboard.

 

In other words, you will be fine; won't be stealing from the graphics card and/or NVMe SSD by adding a PCI-E X1 network / bluetooth card.

Sweet! Thanks man!