Intel 64 and IA-32 Architectures Software Developers Manual Volume 2A, Instruction Set Reference, A-M

Vol. 2 3-695
INSTRUCTION SET REFERENCE, A-M
If CR4.OSFXSR[bit 9] = 0.
If CPUID.01H:EDX.SSE[bit 25] = 0.
#AC(0) If alignment checking is enabled and an unaligned memory
reference is made while the current privilege level is 3.