-mtune=cpu-type Tune to cpu-type everything applicable about the generated code, except for the ABI and the set of available instructions. The choices for cpu-type are: i386 Original Intel's i386 CPU. i486 Intel's i486 CPU. (No scheduling is implemented for this chip.) i586, pentium Intel Pentium CPU with no MMX support. pentium-mmx Intel PentiumMMX CPU based on Pentium core with MMX instruction set support. i686, pentiumpro Intel PentiumPro CPU. pentium2 Intel Pentium2 CPU based on PentiumPro core with MMX instruction set support. pentium3, pentium3m Intel Pentium3 CPU based on PentiumPro core with MMX and SSE instruction set support. pentium-m Low power version of Intel Pentium3 CPU with MMX, SSE and SSE2 instruction set support. Used by Centrino notebooks. pentium4, pentium4m Intel Pentium4 CPU with MMX, SSE and SSE2 instruction set support. prescott Improved version of Intel Pentium4 CPU with MMX, SSE, SSE2 and SSE3 instruction set support. nocona Improved version of Intel Pentium4 CPU with 64-bit extensions, MMX, SSE, SSE2 and SSE3 instruction set support. k6 AMD K6 CPU with MMX instruction set support. k6-2, k6-3 Improved versions of AMD K6 CPU with MMX and 3dNOW! instruction set support. athlon, athlon-tbird AMD Athlon CPU with MMX, 3dNOW!, enhanced 3dNOW! and SSE prefetch instructions support. athlon-4, athlon-xp, athlon-mp Improved AMD Athlon CPU with MMX, 3dNOW!, enhanced 3dNOW! and full SSE instruction set support. k8, opteron, athlon64, athlon-fx AMD K8 core based CPUs with x86-64 instruction set support. (This supersets MMX, SSE, SSE2, 3dNOW!, enhanced 3dNOW! and 64-bit instruction set extensions.) winchip-c6 IDT Winchip C6 CPU, dealt in same way as i486 with additional MMX instruction set support. winchip2 IDT Winchip2 CPU, dealt in same way as i486 with additional MMX and 3dNOW! instruction set support. c3 Via C3 CPU with MMX and 3dNOW! instruction set support. (No scheduling is implemented for this chip.) c3-2 Via C3-2 CPU with MMX and SSE instruction set support. (No scheduling is implemented for this chip.)
While picking a specific cpu-type will schedule things appropriately for that particular chip, the compiler will not generate any code that does not run on the i386 without the -march=cpu-type option being used. -march=cpu-type Generate instructions for the machine type cpu-type. The choices for cpu-type are the same as for -mtune. Moreover, specifying -march=cpu-type implies -mtune=cpu-type. -mcpu=cpu-type A deprecated synonym for -mtune.
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