The PA-8000 (PCX-U), code-named Onyx, is a microprocessor developed and fabricated by Hewlett-Packard (HP) that implemented the PA-RISC 2.0 instruction set architecture (ISA). It was a completely new design with no circuitry derived from previous PA-RISC microprocessors. The PA-8000 was introduced on 2 November 1995 when shipments began to members of the Precision RISC Organization (PRO). It was used exclusively by PRO members and was not sold on the merchant market. All follow-on PA-8x00 processors (PA-8200 to PA-8900, described further below) are based on the basic PA-8000 processor core.