Wikipedia
RDRAND (previously known as Bull Mountain) is an instruction for returning random numbers from an Intel on-chip hardware random number generator. RDRAND is available in Ivy Bridge processors and is part of the Intel 64 and IA-32 instruction set architectures. AMD added support for the instruction in June 2015.
The random number generator is compliant with security and cryptographic standards such as NIST SP 800-90A, FIPS 140-2, and ANSI X9.82. Intel also requested Cryptography Research Inc. to review the random number generator in 1999 and 2012, which resulted in two published papers: The Intel Random Number Generator in 1999, and Analysis of Intel's Ivy Bridge Digital Random Number Generator in 2012.
RDSEED is similar to RDRAND and suitable for producing seed material. The RDSEED generator and processor instruction rdseed are available with Intel Broadwell CPUs and AMD Zen CPUs.