Volume Rendering on OpenCL - 2

OK I moved the same program to a PC with GF 8800 GTX
It runs pretty fast!
12.41 ms(80.51 fps) to render a skull ( 85x96x134 voxels) and
29.19 ms(34.25 fps) with 169x192x268 voxels.
The screen size is also 500x500.

PS. the volume renderer has no lighting, no transfer function lookup.

GPU info:
  CL_DEVICE_NAME:    GeForce 8800 GTX
  CL_DEVICE_VENDOR:    NVIDIA Corporation
  CL_DRIVER_VERSION:    195.62
  CL_DEVICE_TYPE:   CL_DEVICE_TYPE_GPU
  CL_DEVICE_MAX_COMPUTE_UNITS:  16
  CL_DEVICE_MAX_WORK_ITEM_DIMENSIONS: 3
  CL_DEVICE_MAX_WORK_ITEM_SIZES: 512 / 512 / 64 
  CL_DEVICE_MAX_WORK_GROUP_SIZE: 512
  CL_DEVICE_MAX_CLOCK_FREQUENCY: 1350 MHz
  CL_DEVICE_ADDRESS_BITS:  32
  CL_DEVICE_MAX_MEM_ALLOC_SIZE:  192 MByte
  CL_DEVICE_GLOBAL_MEM_SIZE:  768 MByte
  CL_DEVICE_ERROR_CORRECTION_SUPPORT: no
  CL_DEVICE_LOCAL_MEM_TYPE:  local
  CL_DEVICE_LOCAL_MEM_SIZE:  16 KByte
  CL_DEVICE_MAX_CONSTANT_BUFFER_SIZE: 64 KByte
  CL_DEVICE_QUEUE_PROPERTIES:  CL_QUEUE_OUT_OF_ORDER_EXEC_MODE_ENABLE
  CL_DEVICE_QUEUE_PROPERTIES:  CL_QUEUE_PROFILING_ENABLE
  CL_DEVICE_IMAGE_SUPPORT:  1
  CL_DEVICE_MAX_READ_IMAGE_ARGS: 128
  CL_DEVICE_MAX_WRITE_IMAGE_ARGS: 8
  CL_DEVICE_SINGLE_FP_CONFIG:  INF-quietNaNs round-to-nearest round-to-zero round-to-inf fma 

  CL_DEVICE_IMAGE    2D_MAX_WIDTH  8192
     2D_MAX_HEIGHT  8192
     3D_MAX_WIDTH  2048
     3D_MAX_HEIGHT  2048
     3D_MAX_DEPTH  2048

  CL_DEVICE_EXTENSIONS:   cl_khr_byte_addressable_store
     cl_khr_gl_sharing
     cl_nv_compiler_options
     cl_nv_device_attribute_query


  CL_DEVICE_COMPUTE_CAPABILITY_NV: 1.0
  CL_DEVICE_REGISTERS_PER_BLOCK_NV: 8192
  CL_DEVICE_WARP_SIZE_NV:  32
  CL_DEVICE_GPU_OVERLAP_NV:  CL_FALSE
  CL_DEVICE_KERNEL_EXEC_TIMEOUT_NV: CL_FALSE
  CL_DEVICE_INTEGRATED_MEMORY_NV: CL_FALSE
  CL_DEVICE_PREFERRED_VECTOR_WIDTH_ CHAR 1, SHORT 1, INT 1, FLOAT 1, DOUBLE 1