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Video card bandwidth in PCIE3 slot of X570 Taichi?

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foxx1337 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote foxx1337 Quote  Post ReplyReply Direct Link To This Post Posted: 17 Aug 2019 at 4:38am
My Vega56 is plugged into PCI3. This is what hwinfo64 says:


and also 8 GT/s in the Sensor Monitoring window. Looks like PCIe 3 x16 to me.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote ksquared Quote  Post ReplyReply Direct Link To This Post Posted: 16 Aug 2019 at 11:27pm
Originally posted by gizmic gizmic wrote:

Quads are done with 2 dual gpus = pcie1 @ x8 pcie3 @ x8
...
dont know where you get x1 it wont drop that low with all slots populated



OK, now I understand much better. My definition of "all slots" included PCIE2 or PCIE4, since I was thinking there would have to be four graphics cards for "quad."

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Post Options Post Options   Thanks (0) Thanks(0)   Quote gizmic Quote  Post ReplyReply Direct Link To This Post Posted: 16 Aug 2019 at 10:27am
Quads are done with 2 dual gpus = pcie1 @ x8 pcie3 @ x8
3-way = triple at pcie1 @ x8 pcie3 @ x8 pcie5 @ x4

dont know where you get x1 it wont drop that low with all slots populated

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Post Options Post Options   Thanks (0) Thanks(0)   Quote ksquared Quote  Post ReplyReply Direct Link To This Post Posted: 16 Aug 2019 at 5:07am
OK, with the help from everybody here, I am beginning to understand.

Now, what I'm confused about is the specifications state it supports AMD Quad CrossFireX, 3-Way CrossFireX, and CrossFireX. I can understand the CrossFireX with two graphics cards, then both are going at x8 in PICE1 and PCI3.

So how do you do the Quad CrossFireX and the 3-Way CrossFireX? And what will the cards be going at? They all can't go at x8, so maybe with the 3-Way the cards drop to x4? But is the Quad CrossFireX then at x1 for all four cards? Doesn't that somewhat defeat the concept of CrossFireX, especially if everything drops back to x1?

Note: I'm not actually wanting to do any more than one graphics card, but it would be appreciated if I could get to understand it.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Ray62 Quote  Post ReplyReply Direct Link To This Post Posted: 16 Aug 2019 at 4:43am
Originally posted by shmerl shmerl wrote:

Actually, looking closer at that picture, you can see that it's indeed half the width for PCIE3 and quarter of it for PCIE5:
So I suppose this confirms, that PCIE3 is x8 only.


   A picture says more than thousand words.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Xaltar Quote  Post ReplyReply Direct Link To This Post Posted: 15 Aug 2019 at 10:24pm
Yes, it looks like PCIe3 is wired as an X8, x16 is wired across the whole length of the slot.

There shouldn't be any issues using PCIe3 for your GPU, even PCIe 3.0 x4 offers plenty of bandwidth for most modern GPUs. PCIe 4.0 x8 has roughly the same bandwidth as PCIe 3.0 x16 (the bandwidth roughly doubles with each new generation). Similarly, even the bottom x4 slot should be fine as it will perform roughly on par with PCIe 3.0 x8.

I hope this helps ;)
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Post Options Post Options   Thanks (0) Thanks(0)   Quote shmerl Quote  Post ReplyReply Direct Link To This Post Posted: 15 Aug 2019 at 10:14pm
Actually, looking closer at that picture, you can see that it's indeed half the width for PCIE3 and quarter of it for PCIE5:



So I suppose this confirms, that PCIE3 is x8 only.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote shmerl Quote  Post ReplyReply Direct Link To This Post Posted: 15 Aug 2019 at 10:11pm
I guess if the width of the wiring on PCIE5 slot is x4, then PCIE3 is x8 only?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote shmerl Quote  Post ReplyReply Direct Link To This Post Posted: 15 Aug 2019 at 10:09pm
Originally posted by gizmic gizmic wrote:

flip the board around you'll see the pins are different on pcie1 and pcie3. if it only reaches half way its only wired for x8


Heh, I already installed the board. So what exactly do you see on the above picture? The PCIE1 slot wiring is half covered by the shield. Is it the same as PCIE3 or more?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote gizmic Quote  Post ReplyReply Direct Link To This Post Posted: 15 Aug 2019 at 5:40pm
why are you worried on the slot speed you shouldnt have anything that could use it unless its some multi raid card

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