Hewlett-Packard 9825A & 9825B  
Written by Accutron on 2016-04-05  

Devices included in this entry:

Hewlett-Packard 9825A programmable calculator (pictured in thumbnail)
Hewlett-Packard 9825B programmable calculator
Hewlett-Packard 98034A HP-IB Interface
Hewlett-Packard 98036A RS-232C Interface
Hewlett-Packard 98210A String - Advanced Programming ROM
Hewlett-Packard 98216A 9872A Plotter - General I/O - Extended I/O ROM
Hewlett-Packard 98224A Systems Programming ROM

Despite its relative obscurity, the Hewlett-Packard 9825A programmable calculator is the world's first 16-bit microcomputer, and one of the single greatest leaps in computer technology since the invention of the transistor. Introduced in January 1976, more than a year before the first consumer 8-bit personal computers, the 9825A is built around HP's proprietary 16-bit NMOS hybrid microprocessor, providing the 9825A with fast minicomputer-class processing power. The 9825A has an integrated magnetic cassette drive and thermal printer, as well as a wide range of expansion and interfacing options.

The 9825's three-chip hybrid microprocessor consists of the Binary Processor Chip (BPC), Extended Math Chip (EMC) and Input-Output Controller (IOC). The BPC is a single-chip implementation of the core ISA used in the early HP 2100 series minicomputers. The EMC is a floating point processor which executes BCD arithmetic instructions derived from the earlier 9810/20/30 calculators, and the IOC implements I/O, DMA and other related instructions. Together, the three chips are the approximate equivalent of a fully loaded HP 2116 minicomputer CPU with added mathematical functionality.

The 9825A runs HPL (High Performance Language), a proprietary high-level programming language with similarities to APL and BASIC. HPL is an expanded implementation of the programming language used on the 9820A, optimized for calculation and instrument control, and was a personal favorite of HP Labs founder Barney Oliver.

Although it was originally intended as a replacement for the proto-HPL 9820A calculator, the 9825A had evolved to incorporate features from the more computer-like 9830A BASIC system, including the 32-character alphanumeric display, tape drive and QWERTY keyboard. In 1978, HP introduced the 9831A, a renumbered 9825A which omits the HPL interpreter in favor of 9830A BASIC.

In 1980, HP introduced the 9825B, with a revised hybrid microprocessor, full travel keyboard, 23.2K RAM standard, and integrated String, Advanced Programming, Plotter, General I/O and Extended I/O ROMs.While the 9825A retains the multi-level indirect addressing capability of the early HP 2100 series minicomputers, the revised microprocessor in the 9825B abandons multi-level indirect addressing in favor of being able to address up to 64K of memory.

The 9825 had several competitors at the time of its introduction, namely the IBM 5100, Wang PCS II, Tektronix 4051 and Olivetti P6060. The 9825 was faster, lighter and more affordable than any of these competing machines. In particular, the 9825A is nearly 15 times faster than the IBM 5100, released only four months earlier. Although both machines are built upon a 16-bit architecture and are capable of addressing up to 64KB of memory, the IBM 5100 utilizes the board-level PALM (Put All Logic in Microcode) processor. PALM is built from 13 discrete bipolar gate arrays, operating at 1.9MHz. In sharp contrast, the CPU of the 9825A is a three-chip (plus four bidirectional interface buffers) NMOS design mounted on a single leadless carrier, operating at 10MHz. Beyond its raw power, the 9825A also has a superior feature set and range of interfacing options.

Despite its relatively wide adoption, groundbreaking technology and nearly supernatural capabilities, the 9825A has been mostly ignored in the mainstream pantheon of computer history. While the 9825A was eminently affordable to corporate and government entities, it was well outside the price range of consumer hardware which might garner attention from amateur users' groups and mass media. Although the IBM 5100 was in a similar position to the 9825, it has been retroactively deified by computer historians due to its status of being IBM's first 'personal' computer, as well as it having the rather dubious distinction of playing a key role in the John Titor time traveler internet folk tale.

HP also made the marketing mistake of intermittently referring to the 9825A as a calculator or instrument controller, emphasizing its HPL programming language and BCD arithmetic rather than its general purpose capabilities. The original patent for the 9825A refers to it as a calculator, and the codename for the 9825A is 'Keeper', a reference to the key-per-function calculator keyboard originally specified. Feature creep during development eventually outgrew the capacity of a key-per-function interface, and the 9825A was redesigned around a QWERTY keyboard. The vestiges of the original key-per-function keyboard can be seen in the 9825A, which uses a chiclet-style keyboard with metal dome switches, similar to HP's handheld calculators. This keyboard was highly reviled by touch typists, and was replaced with a full-travel Cherry switch keyboard in the 9825B.

9825A-B Operating & Programming Reference (PDF)
9825A System Test Booklet (PDF)
9825A General IO Programming (PDF)
9825A Extended IO Programming (PDF)
HP 9825A-B Service Manual (PDF)
9825A-B CE Handbook (PDF)
98032A-98033A-98034A Interface Cards - Technical Data (PDF)
Calculator Users' Club - Introductory Package (PDF)
US Patent 4075679: Programmable Calculator (PDF)
Nanoprocessor User's Guide (PDF)

Hewlett-Packard 9825A calculator, serial number 1622A07755.

9825A calculator, closeup of display. The 9825A has a single-line 32-character display, built from eight HDSP-2000 alphanumeric bitmap LEDs.

9825A calculator, front-facing ROM slots.

Hewlett-Packard 98210A, 98216A and 98224A ROM cartridges for the 9825A. The ROMs contained on these cartridges are integrated into the 9825B.

9825A calculator, line selector and equipped options.

9825A calculator, view of card cage.

Hewlett-Packard 98036A RS-232C Interface and two 98034A HP-IB interfaces, installed in a 9825B.

Hewlett-Packard 9825B calculator, interface backplane.

9825B calculator, expanded card cage. Note the hybrid microprocessor heatsink in the lower left.

9825B calculator, Keyboard/Display/Printer (KDP) chip.

9825B calculator, display assembly. While the 9825A uses LED displays sealed in red glass, the 9825B uses a similar display sealed in clear glass.

98034A HP-IB Interface, printed circuit assemblies. The heart of the 98034A is HP's proprietary 1820-1691 Nanoprocessor, an 8-bit microprocessor optimized for real-time control.

98036A RS-232C Interface, printed circuit assemblies.

HP Computer & Calculator Products (1966-1976)

This article is part of the [Electronic Calculators] exhibit.

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