HP FOCUS

In 1982, Hewlett-Packard released the FOCUS microprocessor, the first commercially available single-chip CPU that was fully 32-bit. At the time, competitors like DEC, IBM, and Prime Computer relied on multi-chip bit-slice designs, while single-chip offerings such as the Motorola 68000 mixed 32-bit and 16-bit architectures. The FOCUS powered HP’s HP 9000 Series 500 workstations and servers—initially sold as the HP 9020 and sometimes referred to unofficially as the HP 9000 Series 600.

This single-chip CPU worked alongside an I/O Processor (IOP), a Memory Controller (MMU), a clock chip, and multiple 128-kilobit dynamic RAM chips to form the HP 9000 system architecture. It implemented a 32-bit version of the stack architecture found in the 16-bit HP 3000 computer, featuring over 220 instructions (some 16 bits wide, others 32 bits wide), a segmented memory model, and no general-purpose registers visible to the programmer. The FOCUS design drew heavily from HP’s earlier custom silicon-on-sapphire (SOS) chip designs used in the HP 3000 series.

Because HP’s dense NMOS-III process generated significant heat, the chips were mounted on special circuit boards with a roughly 1 mm copper core, called “finstrates.” The FOCUS CPU used microcode stored in a 9,216 by 38-bit control store. All internal data paths and registers were 32 bits wide, and the chip contained 450,000 FETs.