-----Original Message----- From: "Banibrata Dutta" <banibrata.dutta@xxxxxxxxx> To: gcc-help@xxxxxxxxxxx Date: Wed, 9 May 2007 00:19:42 +0530 Subject: AMD64 vs EMT64, compilation & execution Hi, My question in the scope of GCC is, is it guaranteed that Code compiled and linked on AMD64 environment (s.a. AMD Opteron) will run flawlessly in EMT64 environment (s.a. PentiumD w/EMT64), and vice-versa ? Does GCC always guarantee that the processor specific optimization is not used, but only instructions / features common to both AMD64/EMT64 are used in the final binaries ? _________________________________________________- It seems evident to me that you should choose a value of -march= which is compatible with the range of machines you intend to support. The default (omitting -march=) in gcc-4.2 and 4.3 is widely tested for satisfactory operation on both brands. Pentium-D supports sse3 instructions; should you use those (presumably intentionally), your binary would fail on AMD CPUs other than the most recent ones. For gcc-3.4 and 4.1, -march=prescott improves Intel performance without hurting AMD, and does not automatically introduce sse3. gcc x86-64 before 3.4.1 and 3.3.4 did not have satisfactory options for Intel. Tim Prince
