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PetrifiedPenguin88

Graphics Card PCIe Confusion

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Posted · Original PosterOP

I'm a little stumped on some inconsistencies with the Crosshair VI Hero motherboard. The manual (if I'm reading it right) seems to indicate that there is a PCIe 3.0 x16 slot, a PCIe 3.0 x8 slot and a PCIe 2.0 x4 slot. But the advertisement states there's two PCIe 3.0 x16 a 2.0 16x slot and three PCIE 3.0 x1 slots.

 

I am assuming that because the supposed two PCIe 3.0 x16 slots share lanes that the second will only ever utilise 8 lanes and therefor have been marketed as x16 but in reality are x8. Is that correct?

The other question I have is, is the last lane an 2.0 x4 or is it an 2.0 x16 as advertised? 

 

Sstill trying my head around some of the basics so any help is much appreciated.

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9 minutes ago, PetrifiedPenguin88 said:

I'm a little stumped on some inconsistencies with the Crosshair VI Hero motherboard. The manual (if I'm reading it right) seems to indicate that there is a PCIe 3.0 x16 slot, a PCIe 3.0 x8 slot and a PCIe 2.0 x4 slot. But the advertisement states there's two PCIe 3.0 x16 a 2.0 16x slot and three PCIE 3.0 x1 slots.

 

I am assuming that because the supposed two PCIe 3.0 x16 slots share lanes that the second will only ever utilise 8 lanes and therefor have been marketed as x16 but in reality are x8. Is that correct?

The other question I have is, is the last lane an 2.0 x4 or is it an 2.0 x16 as advertised? 

 

Sstill trying my head around some of the basics so any help is much appreciated.

 

On Consumer MB's the top most PCIe x16 slot is electrically connected to 16 lanes, the second one is always 8 lanes, and if a third one exists it's 4 lanes. You can not get "two" x16 slots on any consumer motherboard because no CPU offers more than 24 lanes in order to do so. So it's usually 16 lanes for the GPU, 8 lanes for the second PCIe slot, and then 4 lanes that hang off the PCH chip, that are also shared with the SATA and USB ports.

 

If you put ANYTHING in the x8 slot, it will take 8 lanes from the x16 slot, so you end up with 8x 8x rather than 16x 0x

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Posted · Original PosterOP

Ah ok so basically it's just how they market the product? 

Does that mean that the x4 at the bottom of the card being advertised as x16 is just straight up incorrect? The x4 at the bottom isn't sharing lanes with the two other PCIe slots is it?

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11 minutes ago, PetrifiedPenguin88 said:

Ah ok so basically it's just how they market the product? 

Does that mean that the x4 at the bottom of the card being advertised as x16 is just straight up incorrect? The x4 at the bottom isn't sharing lanes with the two other PCIe slots is it?

It'll be x4 no matter what. It's a x16 slot shape so you can put a x16 card (Eg another GPU) in there, but a SLI/Crossfire configuration like this is usually pointless. Since it's listed as PCIe2.0 I'm kinda wondering if that's true though. Like for my MB:

clip1.png.16c4fc56bb2c5c8ddfaf79ed19687e55.png

Note how it says "3 PCIE Express" but then specifies beside it that 1 at x16 , or 2 at x8 x8 or 3 at 8x 4x x4

 

All other PCIe slots are 2.0 x1.

 

On the Ryzen boards, from the same vendor they're like this:

AMD Ryzen series CPUs (Matisse)
- 3 x PCI Express 4.0 x16 Slots (PCIE1 / PCIE4 / PCIE6: single at x16 (PCIE1); dual at x8 (PCIE1) / x8 (PCIE4); triple at x8 (PCIE1) / x8 (PCIE4) / x4 (PCIE6))*

 

AMD Ryzen series CPUs (Pinnacle Ridge)
- 3 x PCI Express x16 Slots (PCIE1 / PCIE4 / PCIE6: single at Gen3x16 (PCIE1); dual at Gen3x8 (PCIE1) / Gen3x8 (PCIE4); triple at Gen3x8 (PCIE1) / Gen3x8 (PCIE4) / Gen4x4 (PCIE6))*

 

AMD Ryzen series CPUs (Picasso)
- 1 x PCI Express x16 Slot (single at Gen3x8 (PCIE1) or Gen4x4 (PCIE6))*

 

So you can get a 8x 8x 4x configuration on the Ryzen 2xxx and 3xxx chips. At least as far as I can tell. 

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Posted · Original PosterOP
1 minute ago, Kisai said:

It'll be x4 no matter what. It's a x16 slot shape so you can put a x16 card (Eg another GPU) in there, but a SLI/Crossfire configuration like this is usually pointless. Since it's listed as PCIe2.0 I'm kinda wondering if that's true though. Like for my MB:

clip1.png.16c4fc56bb2c5c8ddfaf79ed19687e55.png

Note how it says "3 PCIE Express" but then specifies beside it that 1 at x16 , or 2 at x8 x8 or 3 at 8x 4x x4

 

All other PCIe slots are 2.0 x1.

Ah ok so basically it's x16 size port with x4 lanes available for use. 

 

Ok that makes sense. Bascially if I understand this right, it looks like on your board that 3rd PCIe port does share lanes with the second (being x8 x4 x4 as you said) but that may not be the case for the crosshair and I COULD be looking at x8 x8 x4. 

 

Having said that, looking at the third picture I attached of the graph in my original post it kind of looks to me like it's taking half the lanes from PCIe port 1 (making it x8) but only using the available x4 on the third PCIe port? Does that sound right? If that's the case I'd imagine the crosshair would probably run x8 x4 x4 when using all three ports as well.

 

Either way you've answered the question I was after so thanks very much for all your help. It is much appreciated.

 

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