Features
Announced November 1, 1983, and first shipped in late January 1984, the PCjr—nicknamed "Peanut" before its debut—came in two models: the 4860-004, with 64 KB of memory, priced at US$669 ($1,561 in today's dollars); and the 4860-067, with 128 KB of memory and a 360 KB 5.25-inch floppy disk drive, priced at US$1269 ($2,961 in today's dollars). It was manufactured for IBM in Lewisburg, Tennessee by Teledyne. Roughly 500,000 units were shipped. The PCjr promised a high degree of compatibility with the IBM PC, which was already a popular business computer, in addition to offering built-in color graphics and 3 voice sound that were better than the standard PC speaker sound and color graphics of the standard IBM PC and compatibles of the day. The graphics were produced via a graphics chip known as the VGA—which stood for "Video Gate Array". This was an extension of CGA and should not be confused with the later Video Graphics Array standard that IBM released with the PS/2 line in 1987. The PCjr's sound was provided by a Texas Instruments SN76489 which could produce three square waves of varying amplitude and frequency along with a noise channel powered by a shift register. The PCjr was also the first PC compatible machine that supported page flipping for graphics operation. Since the PCjr used system RAM to store video content and the location of this storage area could be changed, the PCjr could perform flicker-free animation and other effects that were either difficult or impossible to produce on contemporary PC clones.
The PCjr's 4.77 MHz Intel 8088 CPU was faster than other computers aimed at the home market, though the PCjr did not run at the full rated 4.77 MHz because every 4th clock cycle of the 8088 CPU was designated to refresh the PCjr's dynamic RAM as it had no dedicated memory controller; the computer's effective clockspeed was therefore 3.58MHz. The detached wireless infrared keyboard promised a degree of convenience none of its competitors had, eliciting visions of word-processing wirelessly from one's couch with the computer connected to a TV set as a display. Two cartridge slots promised easy loading of games and other software.
Read more about this topic: IBM PCjr
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