422
edits
Changes
GPU
,→Hardware Model
A common scheme on GPUs with unified shader architecture is to run multiple threads in [https://en.wikipedia.org/wiki/Single_instruction,_multiple_threads SIMT] fashion and a multitude of SIMT waves on the same [https://en.wikipedia.org/wiki/SIMD SIMD] unit to hide memory latencies. Multiple processing elements (GPU cores) are members of a SIMD unit, multiple SIMD units are coupled to a compute unit, with up to hundreds of compute units present on a discrete GPU. The actual SIMD units may have architecture dependent different numbers of cores (SIMD8, SIMD16, SIMD32), and different computation abilities - floating-point and/or integer with specific bit-width of the FPU/ALU and registers. There is a difference between a vector-processor with variable bit-width and SIMD units with fix bit-width cores. Different architecture white papers from different vendors leave room for speculation about the concrete underlying hardware implementation and the concrete classification as [https://en.wikipedia.org/wiki/Flynn%27s_taxonomy hardware architecture]. Scalar units present in the compute unit perform special functions the SIMD units are not capable of and MMAC units (matrix-multiply-accumulate units) are used to speed up neural networks further.
{| class="wikitable" style="margin:auto"
|+ Vendor Terminology
|-
! AMD Terminology !! Nvidia Terminology
|-
| Compute Unit || Streaming Multiprocessor
|-
| Stream Core || CUDA Core
|-
| Wavefront || Warp
|}
===Hardware Examples===
* 16 SMs - Streaming Multiprocessors
* organized in 2x16 CUDA cores per SM
* Warp size of 32 threads (number of SIMT threads)
AMD Radeon HD 7970 ([https://en.wikipedia.org/wiki/Graphics_Core_Next GCN)]<ref>[https://en.wikipedia.org/wiki/Graphics_Core_Next Graphics Core Next on Wikipedia]</ref><ref>[https://en.wikipedia.org/wiki/List_of_AMD_graphics_processing_units#Radeon_HD_7000_series Radeon HD 7000 series on Wikipedia]</ref>
* 2048 stream Stream cores @0.925GHz
* 32 Compute Units
* organized in 4xSIMD16/, each SIMT4 , per Compute Unit* Wavefront size of 64 work-items (number ===Wavefront and Warp===Generalized the definition of the Wavefront and Warp size is the amount of threads executed in SIMT threads)fashion on a GPU with unified shader architecture.
=Programming Model=
