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The HP 9000 Computer

The HP 9000 Series 520 was introduced in 1982, and described in the August 1983 Hewlett-Packard Journal as "the new HP 9000 Computer, a mainframe on a desktop for individual engineers and scientists." It could run either HP BASIC, a single-user BASIC environment, or HP-UX, a multiuser UNIX operating system with a full UNIX development environment, including C and FORTRAN 77 compilers.

But was it really the first HP 9000? That depends on your point of view. The HP 9000 Series 236 was available earlier, but was being sold as the HP 9836 (with BASIC, HPL, and Pascal operating systems) and was only later adopted into the HP 9000 product line as the HP 9000 Series 236.

The Hardware

HP 9000 CPU

HP 9000 Series 500 computers were based on a processor architecture called FOCUS, comprising five NMOS-III ICs: a 32-bit segmented stack-architecture CPU (very like the classic 16-bit HP 3000 CPU), an I/O processor (IOP), a memory controller, a 16Kx8 dynamic RAM, and a clock driver. HP's NMOS-III IC process allowed sufficient density and speed that heat dissipation was a problem, and so the ICs are mounted on special printed-circuit boards called "finstrates" -- the printed-circuit board has a 1mm copper sheet at its core, and the IC substrate is epoxied directly to this.

The result of this were three finstrates: CPU, IOP, and 256KB RAM. These were installed in a 12-slot Memory/Processor Module (which is built into the left rear of the Series 520). This permitted configurations of up to 2.5 megabytes of RAM, and also permitted substitutions of memory cards to construct multiprocessor systems -- up to three CPUs and two IOPs could work together in a single system. The Memory/Processor Module generated a 36MHz master clock that was used to drive an 18MHz clock for the CPU; this was sufficient for each CPU to execute one million instructions per second.

Each IOP drove an HP Channel Input-Output (CIO) bus that could support as many as eight I/O devices. This was the first implementation of this bus, but it was later used to support I/O in the early HP 9000 Series 800 and HP 3000 Series 900 systems. Supported I/O devices included HP-IB interfaces, asynchronous serial interfaces, and IEEE 802.3 local area network interfaces. On the Series 520, this bus is built into the right rear of the base cabinet.

The HP 9000 Series 520 also had several built-in I/O devices: a display, which could be either color or monochrome; a keyboard; a floppy-disk drive; an optional internal thermal printer mounted below the display; and an internal hard disk.

Plugging a 27110A/B HP-IB interface into the HP 9000 Series 500 granted access to an array of other devices: most of the HP-IB disk, tape, and disk/tape drives from the HP 79xx family, as well as the HP 9144 cartridge tape drive; some of the HP-IB disk drives from the HP 912x and 913x families; printers such as the HP 2934; and plotters including the HP 74xx family. Similarly, an asynchronous serial interface granted access to just about anything with a serial port, including terminals, modems, printers, and plotters.

Later, a Commercial Memory Controller was developed, along with a one-megabyte Commercial Memory finstrate. This expanded the maximum memory configuration for the HP 9000 Series 500 to 10 megabytes, but also required a new version of the system boot code to properly manage Commercial Memory.

The Software

HP provided a choice of operating systems for the HP 9000 Series 520: BASIC or HP-UX. Both of these were built on top of a common operating system kernel, called the SUN OS (no relation to Sun Microsystems), which provided primitives for the basic allocation and management of memory, processor, and I/O resources. The SUN OS was not intended to be visible to the customer, though.

HP-UX for the HP 9000 Series 500 has the distinction of being the first commercial UNIX supporting a multi-processor system, and by the late 1980s it had become substantially similar to UNIX System V Release 2.

HP-UX provided the HP-IB interfaces with various levels of software. For example, disk and tape drives had corresponding disk and tape drivers, as did printers. But it also exposed the ability to construct device files that could be used to communicate with arbitrary HP-IB devices, and provided a library of C-callable functions for this purpose; this allowed the system to be used for communication with HP-IB-attached test equipment.

© Frank McConnell,

Pictures taken from CHIP 3/1983