The CPUs that are based on x86-64 architecture feature XMM registers (128-bit), recently extended to 256-bit (YMM) and 512-bit (ZMM) for greater capacity. Beyond number crunching, the large registers (YMM and ZMM) are employed in various scenarios, including standard C library functions such as:-  strcmp memcpy strlen Tavis Ormandy, a Google security researcher, found a fresh AMD Zen2 CPU vulnerability enabling data theft at 30KB/sec per core, risking passwords and encryption keys.

Source: GBHackers