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mention SIMD lanes and clarify a little by mentioning SWAR Tags: Mobile edit Mobile web edit Advanced mobile edit |
Array Processors do not ''have'' to have Processing Elements that are SIMD themselves. Tags: Mobile edit Mobile web edit Advanced mobile edit |
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Another key distinction in SIMT is the presence of control flow mechanisms like warps ([[Nvidia]] terminology) or wavefronts (Advanced Micro Devices ([[AMD]]) terminology). [[ILLIAC IV]] simply called them "Control Signals". These allow divergence and convergence of threads, even under shared instruction streams, thereby offering slightly more flexibility than classical [[SIMD within a register]].{{clarify|reason=Is classical SIMD one of the subcategories in Flynn's 1972 paper? If so, which subcategory?|date=July 2025}}
Each hardware element (PU, or PE in [[ILLIAC IV]] terminology) working on individual data item sometimes also referred as SIMD lane or channel, although the ILLIAC IV PE was a scalar 64-bit unit. Modern [[graphics processing unit]]s (GPUs) are often wide SIMD (typically >16 data lanes or channel) implementations.{{cn|date=July 2024}} Some newer GPUs go beyond simple SIMD and integrate mixed-precision SIMD pipelines, which allow concurrent execution of [[8-bit computing|8-bit]], [[16-bit computing|16-bit]], and [[32-bit computing|32-bit]] operations in different lanes. This is critical for applications like AI inference, where mixed precision boosts throughput.
Additionally, SIMD can exist in both fixed and scalable vector forms. Fixed-width SIMD units operate on a constant number of data points per instruction, while scalable designs, like RISC-V Vector or ARM's SVE, allow the number of data elements to vary depending on the hardware implementation. This improves forward compatibility across generations of processors.
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