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Open-Source Radeon Tries Again For PCI-E 2.0

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  • Open-Source Radeon Tries Again For PCI-E 2.0

    Phoronix: Open-Source Radeon Tries Again For PCI-E 2.0

    David Airlie sent in some PCI Express 2.0 patches for the Linux kernel DRM this morning, which will hopefully allow supported Radeon graphics cards to run at PCI-E 2.0 speeds by default...

    http://www.phoronix.com/vr.php?view=MTEyNzM

  • #2
    Woo!

    Glad to see that the attempt is being made. My machines at home all work wonderfully with PCI-E 2.0, and it'll be nice to not have to set a kernel parameter to do it in the future.

    My machines:
    Phenom x3 720 on Gigabyte 780G (built-in HD3200)
    Phenom x6 1055t on Gigabyte 785G (Radeon 6850)
    Llano 3500-series w/ built-in GPU

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    • #3
      I agree, it's nice to see it going in. Hopefully they can weed out the issues popping up when it reaches the broad audiences.

      I've been running with the kernel parameter since Phoronix wrote about how to do it and I've yet to run into any issues. Also running Gigabyte mainboard with a Radeon 4850.

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      • #4
        I have a motherboard here that's not PCIe 2.0 capable (Asus M4N68T LE V2). Howev I don't have a Radeon card to test if it indeed detects that PCIe 2.0 can't be enabled.

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        • #5
          There has to be a big reason why the open source driver is doing so poorly compared to AMD's. PCI-E 2.0 will give you 1-3 fps increase. I remember when ATI made the Radeon 8500, that John Carmack found a bug on their driver that made a huge difference in performance. Can't remember what the bug was.

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          • #6
            Guys

            Guys, I hate to say it, but PCI Express 3.0 is out...

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            • #7
              radeon.pcie_gen2=0

              radeon.pcie_gen2=0

              Why, didn't they just name it radeon.pcie_gen then have it =[1,2,3] instead?

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              • #8
                Originally posted by uid313 View Post
                radeon.pcie_gen2=0

                Why, didn't they just name it radeon.pcie_gen then have it =[1,2,3] instead?
                probably will add something different later, the name is abi now and has been in the kernel for a good while now.

                Dave.

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                • #9
                  PCIE3 isn't needed for graphics yet anyway

                  Once the OpenCL code is running full speed it will become more important to get that supported, but it's not an urgent need yet. Better to focus on other performance optimizations and power management for now.

                  PCIE2 was needed badly, so this is good news.

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                  • #10
                    Originally posted by uid313 View Post
                    Guys, I hate to say it, but PCI Express 3.0 is out...
                    And it offers no gain in performance on even the fastest 16x GPUs on the market, you'll only see a difference on marginal 1x and 4x boards.

                    You can prove this your self by taping over the pins on the card to step down to 8x, 4x and even down to 1x and see how little impact it really has. No, it wont harm the card, the extra lanes don't provide the card with power, only data, all slots be they 1x or 16x supply the same amount of power.

                    only way you'll see a difference is via 3x or 4x crossfire via the PCIe lanes. But there is no Crossfire support yet, is there?
                    Last edited by Kivada; 06-27-2012, 12:43 AM.

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