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HELP...Z170 Pro4s 2 PCIe 3.0 x16 |
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Sovrinn 
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Joined: 17 Mar 2016 Location: Little Rock, AR Status: Offline Points: 4 |
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 Topic: HELP...Z170 Pro4s 2 PCIe 3.0 x16Posted: 17 Mar 2016 at 8:51pm |
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hi guys, i have a issue with my motherboard, when i bought this MB it was advertised that it has 2 X
2 PCie 3.0 X 16, so i bought a second fury and in the radeon software its showing 1x PCIE 3.0 X16 and 1x PCie 3.0 X4 and the performance with 2 cards is worse than just one Fury. can anyone shed some light on what i need to do Thanks
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Xaltar
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Joined: 16 May 2015 Location: Europe Status: Offline Points: 25073 |
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Posted: 17 Mar 2016 at 9:38pm |
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If you look at your manual you will note that it says 1 PCIe x16 at x16 and 1 PCIe x16 at x4, this is the case for all "pro" series and lower ASRock Z170 boards. You should not be getting worse performance with 2 GPUs though, that is not normal. I would use DDU (display driver uninstaller) and remove the drivers then reinstall them fresh.
The board supports up to 4 way crossfire X (2 dual GPU graphics cards) so you should not be having problems. Let us know if the driver reinstall helps.
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parsec
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Joined: 04 May 2015 Location: USA Status: Offline Points: 4996 |
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Posted: 17 Mar 2016 at 11:49pm |
Every and ALL Intel 100 series Skylake chipset/mother boards have only 16 PCIe 3.0 electrical lanes provided by the Skylake CPU. The number of PCIe 3.0 slots on a board, and the number of PCIe 3.0 lanes from the CPU that are connected to those slots will always be limited to the 16 PCIe 3.0 lanes provided by the CPU. Your board's two PCIe 3.0 x16 physical slots are wired electrically as: PCIE2 x16 and PCIE4 x4. But those two x16 physical slots still can only share the 16 PCIe 3.0 lanes provided by the CPU. When both of the PCIe 3.0 x16 physical slots are populated with video cards, and sharing the 16 PCIe 3.0 lanes, they become: PCIE2 x8, PCIE4 x4 electrically. So with your board, using Crossfire causes you to use only 12 of the 16 PCIe 3.0 lanes. That would explain why your performance may be worse when using two cards. |
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Xaltar
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Joined: 16 May 2015 Location: Europe Status: Offline Points: 25073 |
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Posted: 18 Mar 2016 at 12:33am |
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Parsec provided a nice detailed description of how the PCIe lanes are distributed.
Your performance should not be lower with 2 GPUs than with one however. If anything you would be losing out on about 5% - 10% of the second GPUs performance vs a more high end board with x8 + x8 for both GPUs. You should definitely see positive scaling with 2 GPUs which means there is some kind of conflict occurring or the game/benchmark you are using is not recognizing the crossfire setup. The R9 Fury does not use a crossfire bridge so the crossfire configuration occurs via the PCIe slots directly and in software. This is why I suspect your drivers may not be configured properly for crossfire.
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Sovrinn
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Joined: 17 Mar 2016 Location: Little Rock, AR Status: Offline Points: 4 |
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Posted: 18 Mar 2016 at 6:01pm |
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Thanks guys for the responces, i understand now.. needless to say i ordered me a 3 pcie lane , so will be running 3 furys, that should be enough for 2k gameing.
thanks again Sovrin |
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Xaltar
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Posted: 18 Mar 2016 at 6:21pm |
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You're welcome, good luck with the build
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Sovrinn wrote: