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Crossfire & PCIe lanes

BelgianNoise
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Go to solution Solved by airdeano,

the x370 tomahawk lane assignments are shortened: 3 x PCIe 3.0 x16 slots (support x16/x4/x1)

so only the first x16 runs x16 the second x16 slot will only run in x4 not a normal x8 (hence the terrible performance in crossfire)

only real way to correct is a better laid out board.

 

Posted

So I have an RX 580 and an RX 480 in my system. 
The RX 480 I only use for Folding atm.
Everytime I update my radeon software it enables CroosFire again, but the games run slower in crossfire then just on the RX 580.
Somewhere I found that the 580 is running on PCIe x16 and the RX 480 on PCIe x4. I dont recall where I found it in some settings menu. probably in the amd software.

Now, I wanna try and run them in CrossFire but the PCIe x4 on the 480 gives me terrible FPS.
Can i do something about this? or is it PCIe lane bound?
Im using the 8700K on a MSI Z370 TOMAHAWK.

 

I am here to learn, please correct me if im wrong or you see me putting bs on your screen!

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it could be PCIe lane bound. Is the RX 480 on the second X16 slot?

CPU: i7-2600K 4751MHz 1.44V (software) --> 1.47V at the back of the socket Motherboard: Asrock Z77 Extreme4 (BCLK: 103.3MHz) CPU Cooler: Noctua NH-D15 RAM: Adata XPG 2x8GB DDR3 (XMP: 2133MHz 10-11-11-30 CR2, custom: 2203MHz 10-11-10-26 CR1 tRFC:230 tREFI:14000) GPU: Asus GTX 1070 Dual (Super Jetstream vbios, +70(2025-2088MHz)/+400(8.8Gbps)) SSD: Samsung 840 Pro 256GB (main boot drive), Transcend SSD370 128GB PSU: Seasonic X-660 80+ Gold Case: Antec P110 Silent, 5 intakes 1 exhaust Monitor: AOC G2460PF 1080p 144Hz (150Hz max w/ DP, 121Hz max w/ HDMI) TN panel Keyboard: Logitech G610 Orion (Cherry MX Blue) with SteelSeries Apex M260 keycaps Mouse: BenQ Zowie FK1

 

Model: HP Omen 17 17-an110ca CPU: i7-8750H (0.125V core & cache, 50mV SA undervolt) GPU: GTX 1060 6GB Mobile (+80/+450, 1650MHz~1750MHz 0.78V~0.85V) RAM: 8+8GB DDR4-2400 18-17-17-39 2T Storage: HP EX920 1TB PCIe x4 M.2 SSD + Crucial MX500 1TB 2.5" SATA SSD, 128GB Toshiba PCIe x2 M.2 SSD (KBG30ZMV128G) gone cooking externally, 1TB Seagate 7200RPM 2.5" HDD (ST1000LM049-2GH172) left outside Monitor: 1080p 126Hz IPS G-sync

 

Desktop benching:

Cinebench R15 Single thread:168 Multi-thread: 833 

SuperPi (v1.5 from Techpowerup, PI value output) 16K: 0.100s 1M: 8.255s 32M: 7m 45.93s

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  • Solution

the x370 tomahawk lane assignments are shortened: 3 x PCIe 3.0 x16 slots (support x16/x4/x1)

so only the first x16 runs x16 the second x16 slot will only run in x4 not a normal x8 (hence the terrible performance in crossfire)

only real way to correct is a better laid out board.

 

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