First of all, the AMD Radeon HD 7950 graphics card packs 1792 Stream processors, 112 texture units, 32 ROPs, 800MHz core clock, 1.25GHz memory clock, abd 3GB of GDDR5 memory on a 384-bit bus. This graphics card with 4.31 billion transistors has a power limit of 200 Watts and like the Radeon HD 7970 it's core is manufactured on a 28nm TSMC process. These specs are slightly reduced compared to the flagship Radeon HD 7970, but ahead of the Radeon HD 6970 and comes with a $100 price-drop over the current flagship card, which puts its MSRP at around $450 USD. The hardware sounds interesting, but the Linux support for the Radeon HD 7000 series may be questionable.
I've been talking about the Radeon HD 7000 series on Linux for months, but AMD has yet to ship out any Radeon HD 7950/7970 samples for Linux testing. As a result, the Linux information concerning the latest-generation Southern Islands hardware is limited. One of AMD's PR representatives had said he would send out their forthcoming hardware back when at CES earlier this month, but no Radeon HD 7950 3GB card has yet to arrive.
As reported in the earlier Radeon HD 7000 series Linux articles, there was supposed to be Radeon HD 7000 series "launch day" Linux support, but it looks like in reality that didn't happen. Based upon reports in the Phoronix Forums the publicly available drivers at the time considered Southern Islands to be unsupported hardware.
It appears that the recently released Catalyst 12.1 for Linux will work with the Radeon HD 7970, but that OpenCL support is broken. Then there was a special driver release for the Radeon HD 7000 series that's a mix between Catalyst 11.12 and 12.1 that should have OpenCL support, but it isn't the latest upstream release.
In terms of open-source support, there's nothing publicly available yet. The code hasn't been published for the Radeon Linux kernel DRM driver, the corresponding xf86-video-ati DDX changes, or the new Gallium3D driver that's being worked on internally. The "R600g" driver support is being ended with the Radeon HD 6900 series due to significant architectural changes with Southern Islands and a new Gallium3D user-space driver is being written, but is based upon a stripped-down R600g snapshot.
AMD hasn't expressed any timeline for when the Radeon HD 7000 series will actually make it into the upstream repositories, which even at that point will still be a while before most Linux desktop users see it "out of the box" in their distribution. Radeon HD 7000 series support is already out of the question for Ubuntu 12.04 LTS. When the code is also ready for publishing, it still needs to clear AMD's notorious legal review process that can sometimes be lengthy.
The only good news at the moment is that the Radeon VM work and some other prerequisites have landed for the Linux 3.3 kernel, but that by itself isn't for making end-users happy.
That first-cut support will still share the existing open-source Radeon driver limitations: no UVD2 video acceleration (it's still being investigated), there isn't OpenCL support quite yet, and Mesa/Gallium3D is still stuck around OpenGL 3.0. Power management in the open-source Radeon stack is also limited and remains a mess.
In summary, it looks like your mileage may vary right now with the AMD Catalyst Linux driver for the Radeon HD 7900 series and the open-source driver support is still M.I.A. Hopefully soon I'll have some Southern Islands hardware to be able to dig a bit deeper. For those wanting to know how the new Radeon HD 7950 runs under Windows, there's a number of Radeon HD 7950 reviews found by OpenBenchmarking.org and its Cekora engine.