1. Computers
  2. Display Drivers
  3. Graphics Cards
  4. Memory
  5. Motherboards
  6. Processors
  7. Software
  8. Storage
  9. Operating Systems


Facebook RSS Twitter Twitter Google Plus


Phoronix Test Suite

OpenBenchmarking.org

Open-Source Radeon Tries Again For PCI-E 2.0

AMD

Published on 26 June 2012 11:28 AM EDT
Written by Michael Larabel in AMD
12 Comments

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.

As shown in multiple Phoronix articles, PCI Express 2.0 speeds can really boost the Radeon driver performance. With the additional bandwidth provided by PCI-E 2.0, the open-source AMD driver sees a much-needed performance boost. While the PCI Express 2.0 specification was ratified in 2007 and has been supported by most motherboard chipsets and graphics cards since then (on the Radeon side, it's been supported going back to the R600 days), it hasn't been enabled by default with the open-source Radeon driver due to alleged bugs for a small minority of users. The performance meanwhile has been painful for a majority of the ATI/AMD customers sticking to open-source code.

David Airlie began today's patch work by submitting a DRM core patch that allows for checking to see if PCI Express 2.0 5GT link speeds are supported for a given device. There is a special case within this function that explictly disables the PCI Express 2.0 checking for root ports from VIA and Serverworks since they're reportedly known to cause issues.

A second patch allows for PCI Express 2.0 to be supported by the Radeon HD 7000 "Southern Islands" graphics cards, but that patch comes down to just calling the same PCI-E 2.0 initialization path as is used by the HD 6000 "Northern Islands" series, which in turn is the HD 5000 "Evergreen" PCI-E 2.0 code-path.

The third and final patch attempts to enable PCI Express 2.0 support where possible, which comes down to using the new PCI-E 2.0 checker function along the Evergreen (the code-path that's shared with the HD 6000 and HD 7000 series too) and R600 paths. With this patch applied, PCI Express 2.0 should be on-by-default for the Radeon HD 2000 series and newer on a patched Linux kernel in conjunction with a supported PCI-E Gen2 motherboard. If there's bugs, falling back to PCI Express 1.0 is possible via the radeon.pcie_gen2=0 parameter.

Open-Source Radeon Tries Again For PCI-E 2.0 Open-Source Radeon Tries Again For PCI-E 2.0 Open-Source Radeon Tries Again For PCI-E 2.0
Intel's PCI Express 2.0 launch party back in 2007 at IDF Fall prior to the Phoronix computer beer opening event.

These patches will hopefully be merged into the Linux 3.6 kernel to provide a much-needed open-source Radeon driver performance boost. The only problem now? With the Radeon HD 7000 series hardware we're now up to PCI Express 3.0... There's no support there yet on the open-source side (Catalyst on Linux does properly handle PCI-E 2.0/3.0), besides the Gallium3D driver there still not being in a fully-functional state.

About The Author
Michael Larabel is the principal author of Phoronix.com and founded the web-site in 2004 with a focus on enriching the Linux hardware experience and being the largest web-site devoted to Linux hardware reviews, particularly for products relevant to Linux gamers and enthusiasts but also commonly reviewing servers/workstations and embedded Linux devices. Michael has written more than 10,000 articles covering the state of Linux hardware support, Linux performance, graphics hardware drivers, and other topics. Michael is also the lead developer of the Phoronix Test Suite, Phoromatic, and OpenBenchmarking.org automated testing software. He can be followed via and or contacted via .
Latest Linux Hardware Reviews
  1. MSI X99S SLI PLUS On Linux
  2. NVIDIA GeForce GTX 970 Offers Great Linux Performance
  3. CompuLab Intense-PC2: An Excellent, Fanless, Mini PC Powered By Intel's i7 Haswell
  4. From The Atom 330 To Haswell ULT: Intel Linux Performance Benchmarks
Latest Linux Articles
  1. Open-Source Radeon 2D Performance Is Better With Ubuntu 14.10
  2. RunAbove: A POWER8 Compute Cloud With Offerings Up To 176 Threads
  3. 6-Way Ubuntu 14.10 Linux Desktop Benchmarks
  4. Ubuntu 14.10 XMir System Compositor Benchmarks
Latest Linux News
  1. Dead Island GOTY Now Available On Linux/SteamOS
  2. Ubuntu 14.04 In The Power8 Cloud From RunAbove
  3. KDE With Theoretical Client-Side Decorations, Windows 10 Influence
  4. Sandusky Lee: Great Cabinets For Storing All Your Computer Gear
  5. Fedora 21 Beta & Final Release Slip Further
  6. Mesa 10.3.2 Has A Couple Bug-Fixes
  7. RadeonSI/R600g HyperZ Support Gets Turned Back On
  8. openSUSE Factory & Tumbleweed Are Merging
  9. More Fedora Delays: Fedora 21 Beta Slips
  10. Mono Brings C# To The Unreal Engine 4
Latest Forum Discussions
  1. Looking for a Open-Source AMD experienced Linux mentor
  2. Users/Developers Threatening Fork Of Debian GNU/Linux
  3. Updated and Optimized Ubuntu Free Graphics Drivers
  4. HOPE: The Ease Of Python With The Speed Of C++
  5. Use Ubuntu MATE 14.10 Make it an official distro.
  6. Debian Is Back To Discussing Init Systems, Freedom of Choice
  7. AMD Radeon VDPAU Video Performance With Gallium3D
  8. Ubuntu 16.04 Might Be The Distribution's Last 32-Bit Release