Update README.md

Author: devernay

README.md

@@ -49,11 +49,11 @@ env MACOSX_DEPLOYMENT_TARGET=10.6 clang -arch i386 -arch x86_64 -mmacosx-version
 Using the older compilers 
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-Links to the compilers are installed in `/usr/bin` (or `/usr/local/bin` on OS X 10.11 El Capitan): `gcc-4.0` `g++-4.0` `gcc-4.2` `g++-4.2` `llvm-cpp-4.2` `llvm-g++-4.2` `llvm-gcc-4.2`.
+Links to the compilers are installed in `/usr/bin` (or `/usr/local/bin` on OS X 10.11 El Capitan and later): `gcc-4.0` `g++-4.0` `gcc-4.2` `g++-4.2` `llvm-cpp-4.2` `llvm-g++-4.2` `llvm-gcc-4.2`.
 
 GCC 4.0, GCC 4.2 and LLVM GCC 4.2 cannot compile for OS X 10.10 or newer.
 
-PowerPC architectures (ppc, ppc7400, ppc970, ppc64) cannot be linked for OS X 10.7 or newer.
+PowerPC architectures (ppc, ppc7400, ppc970, ppc64) cannot be linked for OS X 10.7 or newer (they would be useless anyway, since PowerPC CPUs were only supported up to 10.5).
 
 Note on Xcode versions
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