Prior to release of the Nvidia GTX 660 Ti, AMD countered with a BIOS update for the Radeon HD 7950 to increase performance.
In preparation to the Nvidia GeForce GTX 660 Ti release, AMD prepared to update the specifications of its Radeon HD 7950 GPU to make it more competitive at its price point. This is a similar move that AMD made after the release of the Nvidia GeForce GTX 670 to make the Radeon HD 7970 more competitive with the release of the HD 7970 1GHz version. With the HD 7950, AMD is updating the HD 7950 similarly to how it handled the Radeon HD 7750: it received a core frequency increase through a specifications update.
AMD has released a new BIOS ROM image file, which works on all AMD reference design Radeon HD 7950 graphics cards that implements the new specifications. The specifications increase the core frequency to 850 MHz (from 800 MHz), and introduces PowerTune with Boost, which sends the clock speed up to 925 MHz (when applications demand it). The other specifications remained the same for the HD 7950, including the memory frequency, stream processor, TMU, and ROP counts. Any Radeon HD 7950 graphics cards manufactured from mid-August and thereafter will feature the new specifications, with no planned price change.
techPowerUp has provided a link to where you can download the updated BIOS, that only works for AMD reference designed Radeon HD 7950's. AMD Radeon HD 7950 Specifications Update BIOS