The difference really is more in the architecture than in the programming model or the instruction set. SIMT programs, such as OpenCL kernels, can indeed be acc

The difference really is more in the architecture than in the programming model or the instruction set. SIMT programs, such as OpenCL kernels, can indeed be accelerated with SSE/AVX, but it is not that efficient (in silicon utilization). Intel's cores are fat cores optimized for single threaded programs. But if you don't care about single threaded performance and optimize for throughput in SIMT programs, the fat core is not a great idea. It is more efficient to hide latency to DRAM with computation rather than through caches, super-scalar and out-of-order execution, register renaming and so on. Expand Intel's SMT (hyperthreading) from 2-threads to 1024-threads, get rid of all the stuff that's there to hide latency and use the saved silicon area to add more cores, and you're looking at something that resembles a GPU.