thanks  Nobuyoshi Nakada. yes ,  VC6 does not supports AMD64

(1).I copy all ""C:\Program Files\Microsoft Visual Studio 8\VC\lib" 
files  to "C:/VClib"

(2).C:\ext>ruby extconf.rb --with-test-dir="C:/sdk" 
--with-test-lib="C:/VClib" --with-test-include="C:\sdk\Include\crt"

now, .manifest was created! ^_^



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