Here are some updated benchmarks of the AMD Radeon HD 7950 "Southern Islands" graphics card under Linux with the proprietary Catalyst driver.
Since publishing the first Radeon HD 7950 Linux benchmarks earlier this month, the GCN graphics card has become "officially supported" via the publicly available Catalyst driver, which means there is no longer any "unsupported hardware" watermark in the lower right hand corner of the display. Additionally, since the unsupported hardware limitations are gone, the aticonfig/amdconfig utility can be used for enabling OverDrive and manipulating the clock-speeds of this high-end graphics card.
With the Catalyst support situation cleared up, there's new OpenGL Linux benchmarks of the Radeon HD 7950 compared to the Radeon HD 6950 while running the Southern Islands graphics card at different clock speeds using the fglrx 8.95.3 / OpenGL 4.2.11554 driver.
The Radeon HD 7950 testing is being done from the XFX Radeon HD 7950 Black 3GB (XFX FX-795A-TNBC), which has the factory overclock set at 900/1375MHz. With now being able to manipulate the clock-speeds, the Radeon HD 7950 was also tested at AMD's reference HD 7950 speeds of 800MHz for the core and 1250MHz for the GDDR5 memory. Additionally, the XFX Radeon HD 7950 was then overclocked further to a 1025MHz core and 1450MHz on the GDDR5 video memory.