OpenGL4.3 Driver : voxel cone tracing is too slow

Hello All,

I am wondering why voxel cone tracing demo is too slow on HD7900 with AMD's openGL 4.3 driver.

I have tried following voxel cone tracing demo.

Voxel Cone Tracing Global Illumination in OpenGL 4.3 - 3D Tech News and Pixel Hacking - Geeks3D.com

Running speed is less than 1fps. I feel this is too slow comparing with nVIDIA GPU.

How can I get more FPS?

(supplement)

1) When I change voxel size from 256x256x256 to 16x16x16, fps incresed to 2.

2) According to geeks3D.com, even nvidia old card is faster.

- GTX560：11fps

  - GTX 680: 30fps

3) My environment is

- HD7900 with 3GB video memory / PCIexpress 2.0x16

- windows 7 64bit

- core i7 980@3.3GHz

- system memory 24GB

- I have installed following driver. I have tried beta1 and beta2, both result is the same.

AMD Catalyst™ OpenGL 4.3 Beta Driver

Thank you in advance.