Although the Battlefield 4 Mantle patch as well as the AMD Catalyst 14.1 beta driver, which actually enables AMD Mantle, are already out, Oxide Games and publisher Stardock have also decided to release a free demo based on the Nitrous Engine with support for AMD Mantle API, the Star Swarm benchmark demo.
Available at Steam, the Star Swarm Benchmark shows some features which will be coming out as soon as someone decide to use the Nitrous Engine. It is based on two fleets of starships and according to developer, you should not take results for granted as repeated runs may produce different results due to high threaded nature of the Nitrous Engine.
According to a couple of early benchmarks with Catalyst 14.1 beta Mantle driver, there are evident performance improvements and we can't wait for more games with support for AMD's Mantle API.
Source:
Steampowered.com.