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Hewlett Packard 9830A Programmable Calculator

Updated 5/2/2024

The 9830A was yet another model in the continuum of the 9800-series. The term continuum is probably a bit misleading, as HP pulled a 'blitzkrieg' on the high-end desktop calculator market by announcing the next generation (after the history-making 9100A & 9100B machines) 9810, 9820, and the 9830 all at nearly the same time in late 1972. The 9830 strayed a bit from the 9810 and 9820, in that it more closely resembles a computer in functionality, while the 9810 and 9820 fall more in the classification of high-end programmable calculators. Though the 9830 can act as a powerful algebraic-entry calculator, the computer-like capabilities become apparent when the powerful programming capabilities of the built-in BASIC programming language are leveraged. In many ways, the HP 9830 is one of, if not the first true Personal Desktop Computers ever marketed. While the 9830 shares many design similarities with the 9810 and 9820 calculators, it is somewhat larger and significantly heavier than its siblings, mostly due to the increased complexity of the machine. The 9830 gains some size and weight as opposed to the 9810 and 9820 by virtue of the larger amounts of ROM, RAM, and support circuitry necessary to provide the function of what, prior to the 9830, used to exist only on large and expensive mini-computer systems. The 9830 is also significantly more expandable than the 9810/9820, with five user-accessible ROM cartridge slots, four internal slots for additional ROM firmware, and four external interface slots. While the 9830 does not have a printer built in like the 9810 and 9820, a port on the back exists for plugging in an external 80-column thermal printer (Model 9866A) that mounts on top of the 9830's cabinet.

HP 9830 with Top Cover Removed (Keyboard toward bottom of photo)

The 9830 shares the same mini-computer-derived 4-board CPU used in the 9810 and 9820 calculators. The CPU board set creates a 16-bit, bit-serial, microprogrammed processor that has a selection of 75 instructions. The architecture of the processor is very similar to that of the 2100-series minicomputers that HP was successfully marketing at the time, with additions to help support performing arithmetic operations in BCD (Binary Coded Decimal) numeric representation. The processor operates operates on data serially, one bit at a time versus the 16-bit parallel operation of the 2100-series minicomputers, making it considerably slower than its minicomputer counterparts, but plenty fast for a desktop computing machine, which was HP's intent for marketing the 9830A, although it in the end, it really was more of a computer than a calculator.

Main ROM Card with Firmware for HP9830 Calculator/Computer

The "operating system" code for the CPU is contained on a ROM card plugged into the backplane of the machine, and can be augmented by the addition of user-added ROM cartridges or internally added ROM boards. The maximum total ROM the machine can contain when fully expanded is 31K of 16-bit words. User-installable ROM modules were available that added additional functionality to the BASIC programming environment, including additional character string handling functions, array and matrix handling functions, enhanced Input/Output facilities, and a special ROM cartridge which turned the 9830 into essentially a computer terminal for use in connecting to larger mini and mainframe computers. With the terminal ROM cartridge, programs for the larger computers could be composed and edited offline using the RAM on the 9830 as a text editor storage area, and when the program was ready, it could be uploaded to the larger computer for execution.

ROM Plug-In Module Compartment (with 3 of 5 ROM slots full)

RAM is used for working data for the machine's overhead needs, as well as for storing user variables, programs, and program state information. Standard RAM is 2048 16-bit words. RAM is expandable to 7616 words. While this seems a very small amount of RAM compared to today's computers, remember that back in those days, memory was quite expensive, and as a result, programs were written to use memory in a much more efficient fashion that we're accustomed to today. The designers at Hewlett Packard that wrote the program that makes the 9830 operate worked very hard to make the code extremely efficient. As a result, it's quite possible for the user to write fairly complex BASIC programs and have them fit within the confines of the limited (as compared to today) memory resources of the 9830. To address the expanding needs for more memory, some third party manufacturers sprung up that provided new, higher-density memory cards for the 9830. HP responded by introducing a follow-on machine, the 9830B, that had more standard RAM to help counter the competition created by these third party memory board manufacturers.

Standard Memory Card for HP9830A

An obvious change from the earlier machines in the 9800-series is the full QWERTY-style keyboard found on the 9830. The keyboard design of the 9830 uses traditional key-switch modules versus the more complex transformer field-sense switch design of the 9810 and 9820 calculators. Because the 9830 has so many more keys than its stable-mates, the cost of implementing the field-sense style keyboard of the 9810/9820 was likely too high to duplicate on the 9830. A full keyboard was needed because in the BASIC language, spelled-out keywords describe the operations to be performed rather than single key presses. The 9810 and 9820 have a dedicated square root key, that, when pressed, causes the square root of the number in the display register to be calculated. For example, to calculate the square root of 1234 on the 9810, the user would key in 1234, then press the [√] key to have the result calculated and displayed. On the 9830, there is no key for the square root function. Instead, the user types out:


and presses the [EXECUTE] key to have the result displayed. "SQR" invokes the square root function, with the argument for the function following inside parentheses. This method involves more key presses, but makes the machine much more general in nature, without having to have a bunch of dedicated or special function keys on the keyboard. There are many different functions provided for mathematical and character string manipulations.

The LED Display Circuit Board of the 9830A

The same 4-character 5X7 dot-matrix LED display modules as those used in the HP 9820 are used for the display on the 9830, however, the number of characters that can be displayed is doubled to 32 characters versus the 16-character display of the 9820. The display on the 9830 will scroll horizontally to handle lines up to 80 characters in length. The 9830 also dispenses with the magnetic card reader used for program and data storage on the 9810 and 9820, in favor of a digital magnetic cassette drive. This drive uses cassettes like those used in old cassette audio tape recorders for storing programs and data. The cassette drive was deemed necessary because of the larger memory storage capacity of the 9830. The size of programs and data on the 9830 simply would not fit conveniently on magnetic card(s).

A Closeup of One of the 4-Character LED Display Modules used on the 9830's Display

The 9830 operates in conversational mode with the user. Expressions can be simply typed into the keyboard, then the [EXECUTE] key pressed for the result of the calculation to be displayed. For example, to calculate the area of a circle with a radius of 10.25 inches, one would type in:


and then press the [EXECUTE] key to display the result of 101.1632742. When programming in BASIC, program statements are entered, and at the end of each statement, the [END LINE] key is pressed. The statement then is analyzed for syntax, and if all is OK, the statement is stored. If a syntax error is detected, the calculator will display an error message indicating what is wrong with the statement, and allow the statement to be edited to correct any syntax mistake made. Once a program has been entered, simply typing RUN and pressing the [EXECUTE] key will cause the program to start up. If any errors are detected during the execution of a program, the machine stops execution and displays an error message, for example:


A slide-out reference card located under the keyboard has a list of the error numbers and their meaning for easy user reference.

The 9830 benefits from an Input/Output architecture similar to that of the 9810 and 9820 calculators, meaning that a wide variety of peripheral devices can be interfaced to the machine. The BASIC programming language of the 9830 made it a natural for jobs like automated test system controllers, data acquisition and processing systems, laboratory instrumentation controllers, and other applications where control of external devices was required. A wide range of peripheral devices were made by HP for connection to the 9800-series calculators, including printers, plotters, instrumentation bus controllers, parallel data ports, digitizing tablets, external cassette tape drives, and even large hard-disk systems that could be shared amongst multiple HP 9830 computers. Third party manufacturers seized the opportunity to build peripheral devices for the 9800-series calculators, that resulted in an even wider variety of external device interfaces, including things like analog to digital converters, digital to analog converters, and relay output modules. With such a wide range of I/O capability, the 9830 became a very popular machine in high technology companies that needed a low-cost, but easily-interfaced computing system.

The Cover of the Simplified 9830 Operating Instruction Manual

The 9830 executes BASIC programs at a fairly decent speed. A simple counting loop will execute just over 100 counts per second. When using the machine as a calculator, basic math calculations return virtually instantaneous results. If a full line (80 characters) complex expression is typed in, the machine can churn for perhaps a second before delivering a result. While running programs or performing calculations, the display is blanked.

The 9830A in base form had a list price of $5,975 at introduction, and the various user-installable ROM packs sold for $485 each. The RAM expansion (option 275), which doubled the amount of memory cost $1,475 if ordered with the machine.

This particular 9830 was built in the mid-1973 time-frame based on date codes and stampings on some of the circuit boards. It was purchased originally by Tektronix in Beaverton, Oregon. One wonders if perhaps this machine was purchased by Tektronix for corporate intelligence reasons -- to find out first-hand information about the competitor's equipment. Tektronix at the time was working on their own programmable calculator, the Tektronix Model 31, to compete with HP and other calculator makers in the high-end programmable calculator marketplace. It's not clear if that was the real reason the machine was purchased, but it's interesting to think about. Tektronix had an Instrument Pool, into which instrumentation would be put in that had either served out its original purpose, or were commonly used items in engineering areas. Any business unit could check out items from the instrument pool on an as needed basis. This 9830A apparently served out whatever requirement it was purchased for, and was relegated to the Instrument Pool. The machine still has the Instrument Pool tags in place. This machine was eventually retired from service in the Instrument Pool, and put up for sale at one of the many fire sales that Tektronix put on for employees in order to liquidate outdated or obsolete equipment.

For much more detailed and comprehensive information on the HP 9830A and other HP calculators, Dave Hicks' fantastic Museum of HP Calculators is a definite must-visit site. Click the link to visit Dave's comprehensive exhibit on the Hewlett Packard 9830.

Text and images Copyright ©1997-2024, Rick Bensene.

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