According to Adobe's AF5.5 New Features document, "After Effects 5.5 introduces important performance improvements, including Pentium 4 optimizations and faster parsing of expressions.", nowhere do they mention Altivec in the 5.5 documents (at least in what's available on the web). However, Altivec support has been present since AF version 4.*, and one would assume that it has been maintained since then...
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According to Adobe's AF5.5 New Features document, "After Effects 5.5 introduces important performance improvements, including Pentium 4 optimizations and faster parsing of expressions.", nowhere do they mention Altivec in the 5.5 documents (at least in what's available on the web). However, Altivec support has been present since AF version 4.*, and one would assume that it has been maintained since then...