HP Series 80

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A running HP-85 with a BASIC listing on its screen

The Hewlett-Packard Series 80 of small scientific desktop computers was introduced in 1980, beginning with the popular HP-85 targeted at engineering and control applications. They provided the capability of the HP 9800 series desktop computers with an integrated monitor in a smaller package including storage and printer, at half the price.


HP-86B with 9121 dual diskette drive

The first model of the Series 80 was the HP-85, introduced in January 1980.[1] BYTE wrote "we were impressed with the performance ... the graphics alone make this an attractive, albeit not inexpensive, alternate to existing small systems on the market ... it is our guess that many personal computer experimenters and hackers will want this machine."[2]

In a typewriter-style desktop case, the US$3,250 (equivalent to $12,000 in 2023) HP-85 contains the CPU and keyboard, with a ROM-based operating system (like the 9800 series), 16 KB dynamic RAM, a 5-inch CRT screen (16 lines of 32 characters, or 256×192 pixels), a tape drive for DC-100 cartridges (210 KB capacity, 650 B/s transfer), and a thermal printer. Both the screen and printer display graphics in addition to text, and the printer can copy anything shown on the screen. The chassis includes four module slots in the back for expansion which can hold memory modules, ROM extensions, or interfaces such as RS-232 and GPIB.[2] All components were designed at the Hewlett-Packard Personal Computer Division in Corvallis, Oregon, including the processor and core chipset.[1]

Later models offered variations such as different or external displays, built-in interfaces or a rack-mountable enclosure (see table below for details).

The machines were built around an HP-proprietary CPU code-named Capricorn running at 625 kHz (0.625 MHz) and had a BASIC interpreter in ROM (32 KB).[3] Programs could be stored on DC-100 cartridge tapes or on external disk/tape units.

Despite the comparatively low processor clock frequency, the machines were quite advanced compared to other desktop computers of the time,[4] in particular regarding software features relevant to technical and scientific use. The standard number representation was a floating point format with a 12-digit (decimal) mantissa and exponents up to ±499. The interpreter supported a full set of scientific functions (trigonometric functions, logarithm etc.) at this accuracy. The language supported two-dimensional arrays, and a ROM extension made high-level functions such as matrix multiplication and inversion available.

For the larger HP-86 and HP-87 series, HP also offered a plug-in CP/M processor card with a separate Zilog Z80 processor.

Historical context[edit]

The late 1970s saw the development of inexpensive home computers such as the Apple II and TRS-80. Steve Wozniak, while working at HP, had developed the Apple computer in his spare time, with the idea of a computer that worked in BASIC when it was turned on. He offered HP rights to the Apple computer, but was turned down and was given a legal release. In an interview he did note that soon after that, the calculator division was starting an 8-bit computer project called Capricorn, and he wasn't allowed to work on that project.[5] Ultimately, the market for desktop computing would go to IBM PC compatible personal computers with a floppy disk drive based operating system, and an industry standard Intel 8088 processor (the IBM PC was announced shortly after the 80 series).



Model Year Price Remarks
HP-85A 1980 $3,250[6] 16 K RAM, 32 K ROM; 5" CRT, 32×16 text or 256×192 graphics; tape drive, printer
HP-83 1981 $2,250[7] same as HP-85 without printer and tape drive
HP-86A 1982 $1,795[8] external composite monitor, no tape drive or printer;
two interfaces for 9130 floppy and one Centronics printer port built in; 64 K RAM
HP-87 1982 $2,495 9" 80×16 (256×128) display, no printer, no tape, built-in HPIB; 32 K RAM
HP-85B 1983 $2,995[9] update to HP-85A; 64 K RAM (32 K program/variables, 32 K RAM disk;
I/O, EDISK, and Mass Storage ROM built in
HP-86B 1983 $1,595[10] update to HP-86; built-in HPIB instead of diskette and Centronics ports; 128 K RAM; EDISK ROM built-in
HP-87XM 1983 $2,995[11] update to HP-87; built-in HPIB; 128 K RAM
HP-9915A/B 1980 $1,675[12] industrial rack-mount version of HP-85A/B without screen or keyboard, I/O ROM and Program Development ROM built in

ROM extensions[edit]

82936A drawer with three ROM modules

Note: The HP-86/87 series used different ROMs (yellow labelling) from the 85/83 models (white labelling).

83/85 86/87 Function Description ID[13]
00085-15003 00087-15003 I/O Access GPIB, serial and parallel (GPIO) interfaces 192
00085-15001 built-in Mass storage Access "Amigo" compatible diskette/disk drives on GPIB. Built into 85B and all 86/87 models. 208
00085-15002 00087-15002 Printer / plotter Support for external printer/plotter (on 86/87 needed for plotter only) 240
00085-15005 00087-15005 Advanced programming Extended Basic commands 232,231
00087-15012 Electronic disk Use part of RAM as a disk drive, built into 85B, 86B. 209
00085-15004 00087-15004 Matrix Mathematical matrix operations including inversion (solving linear equation systems) 176
00087-15004 Matrix 2 Additional matrix operations 177
00085-15007 00087-15007 Assembler Edit and assemble Series 80 assembler source 40
00087-15011 MIKSAM Indexed file record management 14
00085-15013 00087-15013 EMS Extended Mass Storage, access to SS-80 compatible mass storage 207
00085-60952 00087-60912 Service - system Diagnostic routines for service/maintenance 224
? 00087-60913 Service - HPIB Diagnostic routines for service/maintenance 225
98151A Program development Support HP-9915 front panel, or to emulate it on an 83/85 8
AKSO-Sysext Sysext System-Extension: structured programming, self modifying code, low level programmierung, made by Andre Koppel Software[14] 56

Hardware extensions[edit]

Rear of an HP-85B showing the four extension slots
82936A ROM drawer for up to six of the above ROMs (max one per unit)
82903A 16 K memory module, for HP-85A only (max one per unit) Note: *Do not use with HP-85B, may cause damage*
82908A 64 K memory module, for HP-85B or HP-86/87
82909A 128 K memory module, for HP-85B or HP-86/87
82900A CP/M System (for HP-86/87 only). Contains a Zilog Z80 microprocessor and 64 kilobytes dedicated RAM.
82928A System monitor for assembly development. Sets break-points for debugging.
82929A Programmable ROM drawer for standard EPROMs


82940A GPIO Interface, enclosure removed

The interface modules for the Series 80 were built around a proprietary bus interface chip connecting a standard Intel 8049 microcontroller to the main bus. Interface functions such as handshaking were offloaded to the 8049 firmware.[15]

82937A HP-IB Interface (GPIB, IEEE-488, IEC625)
82938A HP-IL Interface
82939A RS-232 Serial interface
82940A GPIO interface (general-purpose 4 × 8-bit parallel)
82941A BCD interface (parallel, 11 binary coded decimal digits + sign)
82949A Printer interface (Centronics parallel interface)
82950A Modem (110/300 bit/s, Bell 103/113)
82966A Data Link Interface (to connect to HP1000/3000 hosts)
82967A Speech synthesis module, 1500-word vocabulary using a Texas Instruments TMS5220 synthesizer chip[16]


  1. ^ a b Lynch, Todd R. (July 1980). "A New World of Personal/Professional Computation" (PDF). Hewlett-Packard Journal. 31 (7): 3–7.
  2. ^ a b Morgan, Christopher P (March 1980). "Hewlett-Packard's New Personal Computer". BYTE. p. 60. Retrieved 18 October 2013.
  3. ^ Lynch, Todd R. (August 1980). "A Custom LSI Approach to a Personal Compute" (PDF). Hewlett-Packard Journal. 31 (8): 16–22.
  4. ^ e.g. Apple II (1977), Tandy TRS-80 (1977), CBM 2001 (1977), Zenith Z89 (1980)
  5. ^ Byte Interview with Steve Wozniak
  6. ^ US$3,250 (equivalent to $12,000 in 2023) (see Inflation Conversion Factors for Dollars Archived 2007-12-30 at the Wayback Machine)
  7. ^ US$2,250 (equivalent to $7,500 in 2023) (ibid.)
  8. ^ US$1,795 (equivalent to $5,700 in 2023) (ibid.)
  9. ^ "Series 80 Personal Computer Price List, July 1, 1983". Retrieved 2010-02-12.
  10. ^ "Series 80 Personal Computer Price List, July 1, 1983". Retrieved 2010-02-12.
  11. ^ US$2,995 (equivalent to $9,200 in 2023) (ibid.)
  12. ^ "HP 9915A Pricing Information, December 1980". Retrieved 2010-02-12.
  13. ^ "ID" refers to the internal ROM identification, i.e. the base address, which needs to be unique in the system.
  14. ^ "SYSEXT-ROM-Manual (german)" (PDF). Retrieved 2016-04-27.
  15. ^ Nairn, John H.; Mikkelsen, Tim I.; Sweetser, David J. (July 1980). "Adding I/O Capability to the HP-85" (PDF). Hewlett-Packard Journal. 31 (7): 7–13.
  16. ^ "HP Computer Museum: 82967A". Retrieved 2010-02-12.

External links[edit]