Capricorn was an 8-bit CPU developed in-house by Hewlett-Packard for its Series 80 machines, which included the HP-85. All its support chips were also custom-developed by HP.

It was relatively slow, running at 0.625MHz, but made up for it by including advanced software features including an impressive 64 8-bit registers, which helped to make it particularly suited to maths and scientific applications. 

It was also unusual in doing calculations in binary-coded decimal by default, with algorithms that derived from HP's years of experience producing scientific calculators. This made Capricorn's calculations demonstrably accurate to 12 digits.