Hewlett-Packard 9820A  
Written by Accutron on 2017-02-28  

Devices included in this entry:

Hewlett-Packard 9820A programmable calculator (pictured in thumbnail)
Hewlett-Packard 11220A Peripheral Control I ROM cartridge
Hewlett-Packard 11221A Mathematics ROM cartridge
Hewlett-Packard 11223A Cassette Memory / Special Programs ROM cartridge
Hewlett-Packard 9820A to 9866A Printer interface

Introduced in 1972, the 9820A is Hewlett-Packard's first algebraic calculator. After the success of the 9100A desktop calculator, HP sought to migrate to a more scalable architecture with their follow-up products, and chose to implement a serialized version of their HP 2100 series minicomputer architecture with added BCD functionality. This approach resulted in the 9810A, introduced in 1971. From a user standpoint, the 9810A was much like the 9100A: a stack-based RPN machine, with key-per-function input and a three line display. Internally, the 9810A was completely different. Instead of using discrete diode and transistor logic with core memory and a CRT display, The 9810A was built from MSI TTL and semiconductor RAM, and had a numeric LED display. The 9810A also introduced the concept of interchangeable ROMs to HP's emerging line of desktop calculators. While the 9100A was an all-in-one machine hardwired to execute trigonometric functions, the 9810A had three ROM cartridge slots above the display, which allowed a user to configure the machine to meet their specific requirements.

After the introduction of the 9810A, HP announced the 9820A and 9830A in the December 1972 issue of HP Journal. The 9820A and 9830A were to become the standard bearers for two new technologies which had recently been developed at HP: NMOS ROM fabrication and alphanumeric dot matrix LED displays. The combination of cheap ROMs and an alphanumeric readout allowed for the implementation of high level language capabilities on both the 9820A and 9830A.

The 9820A is explicitly an upgraded 9810A, with an alphanumeric readout, a larger internal ROM and more RAM. Instead of being a simple RPN machine, the 9820A is programmed in a proprietary high level language. This language would later evolve into HPL on the successor 9825A system. The 9830A is even further removed from the original 9100A concept, with a QWERTY keyboard, 32-line alphanumeric display and BASIC programming.

With the introduction of both the 9830A and HP-35 in 1972, HP's desktop products and calculator products began to diverge. The 9830A was definitively a general purpose computer, and the HP-35 redefined key-per-function scientific calculation as the domain of relatively low-performance handheld devices. To this day, the 9820A stands as the most powerful key-per-function desktop calculator ever built by HP.

The 9820A pictured here was used internally at HP Loveland, and began its life as a 9810A in early 1972. Nearly a year later, it was converted into a 9820A by installing an upgrade kit which replaced the memory components, keyboard and display module. IC date codes on the original 9810A components range from late 1971 to early 1972, while the date codes on the 9820A upgrade components are from late 1972. As this machine was an internal use system, it lacks a traditional serial number placard, and has a nonstandard number placard and a 'NOT CAPITAL ASSET' sticker below the ROM function keys.

9820A Operating & Programming (PDF)
9810A / 9820A Calculator Service Manual (PDF)
9820A Brochure: "Meet the Conversational Calculator" (PDF)
9820A Calculator - Technical Data December 1972 (PDF)
Series 9800 Pricing Information (PDF)

Hewlett-Packard 9820A programmable desktop calculator with Option 001, 429 total registers.

The 9820A readout is constructed from four horizontally stacked Hewlett-Packard 5082-7101 four-digit alphanumeric LED displays.

9820A calculator, card cage. The 9810A / 9820A processor consists of four PCAs installed in the primary backplane, and two additional 'M' and 'T' register PCAs included in the memory subsystem - 128 ICs in total. The entire memory subsystem is housed in an aluminum box, mounted on a daughter backplane (far left.)

09810-69513 'Micro Processor' card. Note the TI SN71450N 16:1 multiplexer, and six Intel 3301A 256x4-bit static ROMs. Some of the ROMs have Intel branding and dual part numbers, while others only have HP markings.

The 9820A memory subsystem is a separate card cage which sockets into the main backplane.

9820A RAM card. There are two such cards in the memory subsystem, each with 16 Intel 1103 1kbit dynamic RAM ICs.

9820A ROM assembly.

9820A ROM cartridges: 11220A Peripheral Control I, 11221A Mathematics and 11223A Cassette Memory / Special Programs. Note the dark grey housings of the 11220A and 11221A, which may indicate that they are production prototypes. No other examples of 9820A ROMs in this color are currently known.

11221A and 11223A ROM PCAs. These ICs were manufactured by HP, using their first-generation NMOS fabrication process.

Hewlett-Packard 9820A to 9866A Printer interface, formerly the property of HP engineer Leo Miller, who designed the 9810A and 9820A displays as well as the power supply for the 9866A printer.

9820A to 9866A interface, internal construction.

HP Computer & Calculator Products (1966-1976)

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

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