DXT5N & 3Dc(aka BC5) compression in common code & SIMD:
http://mrelusive.com/publications/papers/Real-Time-Normal-Map-Dxt-Compression.pdf
Others:
dxt1 real time compression
http://www.nvidia.com/object/real-time-ycocg-dxt-compression.html
real time compresion using SIMD & Intel TBB
https://software.intel.com/en-us/articles/fast-cpu-dxt-compression