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Help with HD 7870 XT Tahiti Crossfire

Question asked by planarfreak on Apr 19, 2018
Latest reply on Apr 21, 2018 by planarfreak

Hello Forum,

 

I need help with setting up Crossfire for a pair of HD 7870 XT video cards, and I'm open to all ideas and suggestions.

I've always wanted to try out Crossfire - my original card was purchased new in 2013, and I purchased the second  recently from eBay.

 

Here's the required information.

 

Describe your system:

  • AMD Graphics Card
    • Sapphire Radeon HD 7870 XT, Bios 015.030.000.002
    • PowerColor Radeon HD 7870 XT, Bios 015.032.000.000
    • They have the exact same factory default specs and settings - Tahiti architecture, 2048 MB of GDDR5 memory, 1500 MHz memory, 975 MHz clock, PCI 3 bus
    • I've tested both of them individually in the primary slot, both work fine.
    • They are currently inserted in the first and second slots, with the crossfire bridge attached. Both are detected in the settings (first as Discrete/Primary, second as Discrete)
      • Edit: "First" and "Second" as in "Primary" and "Secondary" - the slots are labeled PCIE2 and PCIE3 on my MOBO. PCIE1 is a small 1x slot.
  • Desktop or Laptop System
    • Desktop
  • Operating System
    • Windows 7 SP1, 64bit
  • Driver version installed
    • 18.2.1 Adrenaline
  • Display Devices
    • Samsung S34A350H 1920x1080 at 60Hz with HDMI
  • Motherboard + Bios Revision
    • ASROCK Z87 Extreme6 (crossfire compatible, operating at x8 in dual configuration)
  • CPU/APU
    • Intel i5-4670k
  • Power Supply Unit  Make, Model & Wattage
    • Corsair AX 850 Gold (850W)
  • RAM
    • 16GB

Describe your issue:

  • My issue is that I cannot see the crossfire option in the global settings (where I'm told it should be).
    • Both cards are detected in settings (first as Discrete/Primary, second as Discrete)
    • Both cards can be controlled with Global Overdrive (I tested this using the manual fan speed slider)
  • Any ideas?
  • Bonus question: what's a good benchmark test to use to see the improvement?

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