HP FOCUS
First commercial single-chip fully 32-bit microprocessor.
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.
- Launch year
- 1982
- Bit width
- 32-bit
- Transistor count
- 450,000 FETs
- Instruction count
- Over 220 instructions
- Microcode control store
- 9,216 by 38-bit
- Process technology
- NMOS-III
- Architecture origin
- 32-bit implementation of the 16-bit HP 3000 computer's stack architecture
Lore & Background
The FOCUS CPU was a 32-bit implementation of the 16-bit HP 3000 computer's stack architecture, featuring over 220 instructions (some 32 bits wide, some 16 bits wide), a segmented memory model, and no general purpose programmer-visible registers. Its design was richly inspired by the custom silicon on sapphire (SOS) chip design HP used in their HP 3000 series machines. The single-chip CPU was used alongside the I/O Processor (IOP), Memory Controller (MMU), Clock, and a number of 128-kilobit dynamic RAM devices as the basis of the HP 9000 system architecture.
Because of the high density of HP's NMOS-III IC process, heat dissipation was a problem. Therefore, the chips were mounted on special printed circuit boards with a ~1 mm copper sheet at its core, called "finstrates." The Focus CPU is microcoded with a 9,216 by 38-bit microcode control store, and internal data paths and registers are all 32-bit wide. The Focus CPU has a transistor count of 450,000 FETs.
Reader's Guide
The FOCUS microprocessor holds significance as the first commercial single-chip fully 32-bit microprocessor, arriving in 1982 when all 32-bit competitors such as DEC, IBM, and Prime Computer used multi-chip bit-slice-CPU designs. Single-chip designs like the Motorola 68000 were a mix of 32 and 16-bit, making FOCUS a milestone in processor integration. Its stack architecture, inherited from the HP 3000, and lack of general-purpose programmer-visible registers represented a distinctive design philosophy. The use of NMOS-III process required innovative thermal management via finstrates—copper-core circuit boards. The FOCUS CPU's microcoded control store and 32-bit internal data paths underscored its advanced design for the era. Its legacy lies in demonstrating that a full 32-bit implementation on a single chip was feasible, paving the way for later single-chip 32-bit processors in the industry.
Did You Know?
- It had no general purpose programmer-visible registers.
- The FOCUS CPU had a transistor count of 450,000 FETs.
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