Useful Notes / IBM PCjr

IBM's attempt at competing with the original Apple ][, the IBM Personal Computer, was a success. For a followup, it decided to enter the already-crowded 8-bit home computer market and compete against the Commodore 64 and the Atari 8-Bit Computers with the IBM PCjr, which it released to much fanfare in 1983.

The PCjr was deliberately made to be simple to put together, simple to use, and simple to locate. It had a much smaller case than a regular PC, about the size of the original Xbox, and used a power brick instead of the full-size power supply the contemporary IBM PC/XT used. The floppy drive was optional, like on the original PC, and under it were two cartridge slots, much like the Atari 800. Graphics and sound-wise, it was the best MS-DOS machine around for years. IBM designed an entirely new video controller for the PCjr, and it was the first IBM PC to have a proper 16-color graphics mode. It also had real polyphonic sound thanks to a TI PSG chip. The PCjr also included an infrared wireless keyboard (with an option to wire it to the console if desired), and could be had with its own custom monitor with a built-in speaker.

All of this came at a cost, though. The PCjr was far more expensive than either the C=64 or the Atari machines, and wasn't good enough with graphics or sound to justify the price. The keyboard was a "chiclet" keyboard, outwardly similar to today's laptop keyboards but cheaply made without such modern amenities like scissor mechanism or mechanical switches,note  and thus extremely mushy, so most people found it hard to type on; also, the infrared link was iffy from more than a few feet away, making the computer difficult to use from across the room or the couch. IBM also deliberately crippled the machine in other ways so that normal PC and XT software would have a hard time running actually, the very same mistake that killed Apple III.

Another point of contention was that normal PC peripherals wouldn't connect without adapters, if at all instead of the enthusiastically adopted expansion card architecture of the original IBM Personal Computer, PCjr used a clumsy "sidecar" system, which required a lot of desk space and additional power supplies for any serious expansion. While this didn't stop the diehards, many people who bought a PCjr bought it in the hopes that their PC-based office software would run on it, only to be in for a nasty surprise when they got it home. Bad keyboard that made typing anything on it a chore, didn't help either back in The '80s the quality of a home computer keyboard (a frequent target for penny-pinching suits) was no less important consideration in the platform choice than graphics or memory size (which were also underwhelming compared to its competitors).

Given all that, the PCjr was a flop for IBM. After 2 years of slow sales and poor reviews, it was quietly discontinued in 1985. However, despite its poor sales and compromised design, someone had already decided to clone it, and in the process, fix some of its quirks. That someone was Tandy Computers, of TRS-80 fame, who was looking to move into the PC-compatible market and decided the PCjr was the machine to beat, flop or no flop. The result of this was the Tandy 1000 line of multimedia PCs, which were decent sellers until their discontinuation in the mid-1990s, while establishing the PC as a viable gaming platform. It's no accident that the computer game market in the U.S. shifted from the C64 to the PC in the second half of the '80s. This had an interesting side effect, in that certain games for the Tandy 1000 could run on the PCjr in 16-color mode with only minor patching. Also, third parties such as Racore and PC Enterprises made several add-ons for the PCjr that restored some of the XT's lost capabilities, provided more room for expansion, and added extra features.


  • CPU: Intel 8088, 4.77 MHz.
  • GPU: Motorola 6845 + IBM custom Video Gate Array ("VGA") ASIC, providing up to 16 colors in 320x200 mode; mostly CGA-compatible, used 16k of shared system RAM that could be relocated if needed.
  • Storage: Two proprietary memory cartridge slots on the front; optional 360k DS/DD floppy drive or cassette cable.
  • Audio: Texas Instruments SN76489 PSG, with 3 square-wave channels and one noise channel.

Games with an affinity towards this system: