The SuperI/O is the part of the southbridge (which later became the ICH and nowadays is known as PCH) that implements the legacy ISA chips (RTC, 8042[1], 8254,

The SuperI/O is the part of the southbridge (which later became the ICH and nowadays is known as PCH) that implements the legacy ISA chips (RTC, 8042[1], 8254, 8257, 8259). It used to be separate, which was already an improvement over the separate integrated circuits of 30 years ago. [1] nowadays the 8042 is mostly emulated in SMM because it needs to convert USB to PS/2.