X11 is a chained hashing algorithm approach, taking 11 hashing algorithms from the sphlib. Created by Evan Duffield, X11 consists of blake, bmw, groestl, jh, keccak, skein, luffa, cubehash, shavite, simd, and echo.
NIST5 is more efficient than X11 with GPU. And for now is ASIC restirant, and X11 no.