AMD added its R9 M400 Series of mobile GPUs on their website, with specifications.
As we can see for specs AMD R9 M400 mainstream segment mobile GPU, with 32 Compute units and offer 5.5TFLOPs of GPU performance with TDP lower than 150W, backed by 8GB GDDR5 memory clocked a 1250MHz on a 256-Bit interface.
Those specifications indicate the new R9 M400 GPU will deliver around the same compute performance as AMD’s Hawaii-based R9 290W but in half the TDP.
The other two GPU are R9 M470X and R9 M470, both entry level GPUs with 14 and 12 compute units with 4GB GDDR5 1500MHz memory on a 128-Bit interface. Which will provide decent performance for 720p laptop market.