Your board's chipset only supports PCIe 2.0, so operation is negotiated down to there.
I knew that much, but what about the card being identified as x8? Would the negotiation include staying in x8 to save power?
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The board has the following add-in card connectors:
• PCI Express 2.0 x16: one PCI Express 2.0 x16 connector supporting simultaneous transfer speeds up to 8 GB/s of peak bandwidth per direction and up to 16 GB/s concurrent bandwidth.
• PCI Express 2.0 x1: two PCI Express 2.0 x1 connectors. The x1 interface supports simultaneous transfer speeds up to 2.5 Gb/s of peak bandwidth per direction and up to 5.0 Gb/s concurrent bandwidth.
After checking specifications of the XFX Radeon R7 240, this is up to x8.
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Well, since your graphics card is plugged into the (one and only) PCIe x16 slot, I would have thought that the negotiated interface would have ended up being PCIe 2.0 x16.
Try displaying the information using a (smarter?) tool like AIDA64 and see what it says the interface actually is...
I'm so ticked. I read that webpage before I posted my question, but I only looked at SPECS, the logical place for a technical tidbit like that. But on the FEATURES page, it clearly states "PCI Express 3.0 x8 bus interface." So PCIe negotiation only works between PCIe 2.0 and PCIe 3.0. Thanks for the homework.
I tried AIDA64 Extreme and now I know why you recommend it. It's an encyclopedia of PC data. It verified that the board slot is x16, but I did not see any place where the card width was specified, but then again my eyes glazed over after reading a few thousand lines.