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*''{{vanchor|[[SIMD]] instruction|SIMD instruction}}s'', a single instruction performing an operation on many homogeneous values in parallel, possibly in dedicated [[SIMD register]]s
*performing an atomic [[test-and-set]] instruction or other [[read–modify–write]] [[atomic instruction]]
*instructions that perform [[arithmetic logic unit|ALU]] operations with an operand from memory rather than a register: exceptions to this rule being architectures that were designed as memory-based from the ground up, such as the [[CDC STAR-100]] and to an extent Accumulator-based machines such as [[Atmel]] [[PIC microcontrollers]].
Complex instructions are more common in CISC instruction sets than in RISC instruction sets, but RISC instruction sets may include them as well. RISC instruction sets generally do not include ALU operations with memory operands, or instructions to move large blocks of memory, but most RISC instruction sets include [[Single instruction, multiple data|SIMD]] or [[vector processing|vector]] instructions that perform the same arithmetic operation on multiple pieces of data at the same time. SIMD instructions have the ability of manipulating large vectors and matrices in minimal time. SIMD instructions allow easy [[parallelization]] of algorithms commonly involved in sound, image, and video processing. Various SIMD implementations have been brought to market under trade names such as [[MMX (instruction set)|MMX]], [[3DNow!]], and [[AltiVec]].
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