parallelization techniques at the instruction level of a processing element (e.g. pipelining, SIMD processing)
advanced instruction sets that improve parallelization (e.g., AVX-512)
hybrid approaches, e.g. combining CPUs with GPUs or FPGAs
typical network topologies and architectures used for HPC systems, like fat trees based on switched fabrics using e.g. fast Ethernet (1 or 10 Gbit) or InfiniBand