31 Facts About IBM PCjr

IBM PCjr was a home computer produced and marketed by IBM from March 1984 to May 1985, intended as a lower-cost variant of the IBM PC with hardware capabilities better suited for video games, in order to compete more directly with other home computers such as the Apple II and Commodore 64.

The IBM PCjr supported expansion via "sidecar" modules, which could be attached to the side of the unit.

Front of the IBM PCjr exposes a pair of cartridge slots in which the user can insert software on ROM cartridges, as was common with other home computers.

IBM PCjr graphics were similar to CGA, with several new video modes:.

The CGA did not provide a VBLANK interrupt, making it hard to detect when the screen was beginning to be drawn, but the IBM PCjr provides this on IRQ 5, an important feature for smooth page-flipping.

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Unlike CGA, IBM PCjr has palette registers which allow the colors in all modes to be chosen from the full 16-color RGBI palette.

Monitor included with the IBM PCjr is a TTL RGBI display like those supported by the CGA, but including an internal amplified speaker.

Also like CGA, the IBM PCjr supported composite video out for use with a TV or composite monitor.

Motorola 6845 CRTC like the one used in the MDA and CGA adapters, and a custom IBM chip called the Video Gate Array comprise the PCjr video hardware.

IBM PCjr's sound is provided by a Texas Instruments SN76496 which can produce three square waves of varying amplitude and frequency along with a noise channel powered by a shift register.

The IBM PCjr design allows for an analog sound source in an expansion-bus "sidecar" module, and a software-controlled internal analog switch can select the source for the sound output from among the PC speaker, the SN76489, the cassette port, or the expansion-bus sound source.

The IBM PCjr keyboard has 62 keys rather than the 83 of the PC keyboard, and the remaining keys must be entered by holding a shift key.

IBM PCjr sold a cable which could be plugged in between the keyboard and computer if the user wanted a more reliable connection, which eliminated the need for batteries, since the keyboard IR receiver is automatically disabled when the cord is attached to the computer.

Chiclet design was not well received, and in 1984 IBM PCjr began shipping a new design, still wireless, but using more conventionally shaped keycaps.

Internally the IBM PCjr did have expansion slots to support specific upgrades: a RAM upgrade, a modem, and a floppy drive.

The IBM PCjr has a "gate" register to which software writes the number of the video register to be accessed, followed by the value to be written into it.

IBM PCjr repeatedly denied these rumors, but customers visited stores attempting to buy the product and rivals' revenue, product plans, and share prices reacted to the officially nonexistent computer in what the press called "Peanut Panic" or "The Great Peanut Roast".

Adweek estimated that IBM PCjr would spend on marketing, including an alleged license of Charles Schulz's Peanuts characters.

IBM PCjr was released in March 1984, missing the 1983 Christmas sales season due to production delays.

IBM PCjr allowed them to postpone paying for inventory for 180 days, but inventory continued to pile up.

IBM PCjr's cost was its biggest disadvantage, even more so than the keyboard.

IBM was surprised to learn that many of the initial customers for the PCjr were not home users as they assumed, but instead businesses who wanted a cheaper PC that took less space on a desk.

IBM PCjr failed to recognize that many consumers wanted a computer more sophisticated than those that cost less than, but did not want to spend more than.

The IBM PCjr's price was close to that of the Coleco Adam, but the Adam included a tape drive, a printer, and software.

Ultimately, the IBM PCjr was perceived as not having a killer app to make up for these limitations.

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The IBM PCjr lacks a DMA controller, so the 8088 CPU has to service floppy disk transfers directly, causing the system to momentarily freeze while accessing a disk.

IBM PCjr reportedly became the best-selling computer, outselling the Apple IIe and IIc by four to one in some stores and even the C64.

Inventory remained through Christmas 1985, and IBM PCjr used discounts as well as radio and full-page print ads to try to sell off remaining stocks.

The failure was so great that it was compared to the Edsel and New Coke, and IBM PCjr reportedly created a Chiclet rule, requiring human factors testing for future products.

The IBM PCjr's enhanced graphics and sound standards became known as "Tandy-compatible", and many PC games advertised their Tandy support.

The IBM PCjr was able to run other software designed for the PC, such as word processor, database and spreadsheet programs ran well on the IBM PCjr with 128K of memory.