I was searching the MW forum for the post concerning the GPU n-body app. It is lost somewhere in there but I did find a reference to the AMD Accelerated Parallel Processing OpenCL Programming Guide. While perusing the document I discovered Appendix-A.
Here is a summary of what it contains:
AMD Accelerated Parallel Processing OpenCL Programming Guide
Date of printing: December 2010
Appendix A (page-117)
OpenCL Optional Extensions
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A.8 AMD Vendor-Specific Extensions (page-120)
This section describes the following extension:
cl_amd_fp64
cl_amd_device_attribute_query
cl_amd_event_callback
cl_amd_media_ops
cl_amd_printf
• cl_amd_fp64 — Before using double data types, double-precision floating
point operators, and/or double-precision floating point routines in OpenCL™
C kernels, include the #pragma OPENCL EXTENSION cl_amd_fp64 : enable
directive. See Table A.1 for a list of supported routines.
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A.9 Supported Functions for cl_amd_fp64 (page-124)
Table A.1 lists the functions supported by cl_amd_fp64 on three platforms...
Note: The three platforms are Evergreen(5xxx) RV770(4xxx) x86 CPU
You will see that Evergreen has support for most of the OpenCL cl_amd_fp64 functions and all RV770 support is listed as Beta (Beta = Not Working)
So it is clear that at this point in time the RV770 (HD 4xxx Series) cannot perform OpenCL Double Precision funtions. Since AMD no longer supports production of the RV770 GPU why would they continue to develop OpenCL support for it?