Will GPU differences in otherwise identical cards prevent Crossfire from working?

[Red Suspense]

Well, ladies and gentlemen, I’m completely stumped after a lot of Crossfire problem-solving. Even though both cards had the exact same item number on Newegg (checked my receipts), they were purchased a year apart and to my surprise, one is built with a Pitcairn GPU and one with Tahiti. They’re both XFX AMD R7870 double-dissipation 2GB, GHz edition, both PCI-e 3.0, DDR5. Does that GPU difference prevent Crossfire from working?

My new system is based on a MSI Z87-G45 gaming motherboard w 32 GB memory, and Catalyst Control Center does not display the Crossfire option in Gaming, Performance, or anywhere else. According to GPU-Z, both cards work correctly, and I’ve run the monitors through each card to verify that they work. GPU-Z describes both cards as “AMD Radeon HD 7800 series.”

Googling around, I removed and re-seated the cards, changed the crossfire ribbon cable, removed AMD drivers via Display Driver Uninstaller, reinstalled Catalyst Control Center, and nothing is different. The graphics cards are in the correct crossfire slots per the mobo’s manual (#2 and 5). I’ve got to make the return decision pretty quickly if the issue is GPU incompatibility. Your advice is appreciated.

 

[Red Suspense]

Just got a definitive answer from XFX technical support. Yes, even though both cards are XFX 7870s, a 7870 with Pitcairn processors will not Crossfire with a 7870 with a Tahiti processor. Surprisingly, though, as a win-win they offered to replace my Tahiti with a 2nd Pitcairn; I suppose that they can make more money off a refurbished Tahiti then they can over an obsolete Pitcairn. Fine with me.