Diablo 630 (Daisy Wheel Printer)

What the Diablo 630 was

The Diablo 630 was a daisy-wheel computer printer marketed by Diablo Systems, Inc., the Diablo Data Systems division of Xerox Corporation; Computer History Museum records label surviving units "Diablo Systems Inc., A Xerox Company." It was a letter-quality impact printer, meaning it struck fully formed characters through an inked ribbon rather than building them from a pattern of dots. Wikipedia describes its output as equivalent to an IBM Selectric typewriter — the de facto quality standard of the period — produced at a nominal 30 characters per second. Physically it was a desktop unit: two Computer History Museum catalog entries give dimensions of roughly 23½ inches wide by 8 inches high by about 19 inches long, and a weight of about 35 to 40 pounds.

How daisy-wheel, letter-quality printing worked

Like other daisy-wheel machines, the 630 formed characters using a flat wheel of radial spokes, or "petals," each carrying one raised character at its tip. To print a character the wheel spun to bring the correct petal into position, and a hammer struck it against an inked ribbon and the paper. Because each glyph was a solid, pre-formed shape, the result read like typewriter output — the origin of the "letter-quality" label. This impact approach contrasts with dot-matrix printing, which builds characters from patterns of pins and trades crispness for speed and graphics capability. Wikipedia notes that Diablo Systems had developed the first commercially successful daisy-wheel printer around 1970 under engineer Andrew Gabor, and the 630 was a mature, widely sold member of that lineage.

The interchangeable print wheel

A defining feature was the removable print wheel. As with the changeable "typeball" element of the IBM Selectric, an operator could swap the wheel to change typeface or character pitch, according to Wikipedia. The Computer History Museum's history "The Daisy Wheel Story," co-written by Diablo figures Michael Weisberg and George Comstock, credits the Model 630 with "Mike Weisberg's new very low cost, extremely durable print wheel" and says the model "became the market's undisputed favorite." The University of Amsterdam computer-museum record for a later 630 ECS/IBM variant describes a 96-petal plastic wheel carrying two characters per petal — 192 characters in all — with the wheel jogging slightly to reach the inner character.

Dating the Diablo 630

Authoritative sources disagree on when the 630 appeared, so this page does not assert a single introduction date. The Computer History Museum's "The Daisy Wheel Story" states the Model 630 was "introduced in 1976," whereas Wikipedia says the printer was sold by the Diablo Data Systems division of Xerox "beginning in 1980." Computer History Museum catalog records for individual units date them to 1980 and to about 1982. No discontinuation date could be traced to an authoritative source, so none is stated here; figures that cannot be verified are omitted rather than estimated.

A de facto standard: Diablo 630 emulation

The 630's most durable legacy was its command set — the escape sequences a computer sent to control margins, line spacing, pitch, and other functions. Wikipedia states the Diablo 630 was so successful that "virtually all later daisy wheel printers, as well as many dot matrix printers and even the original Apple Laserwriter either copied its command set or could emulate it," and that "Diablo emulation became an expected feature" on other daisy-wheel and early laser printers. In that respect the 630's control language played a role comparable to other de facto printer-control standards, such as Epson's ESC/P, by giving software a common target to write to.

Interfaces: Centronics, RS-232, and the API

Wikipedia records that the 630 could originally be ordered with either a Centronics parallel or an RS-232 serial interface. Diablo later introduced the API (All Purpose Interface), after which RS-232, Centronics, and GPIB (IEEE-488) were available on every printer. Serial baud rates were configurable; the University of Amsterdam record for the ECS/IBM variant lists options of 110, 300, 1200, and 2400 baud together with a roughly 1,300-character receive buffer.

Variants and OEM versions

Several variants existed. Wikipedia describes the 630 ECS (Extended Character Set), whose wheels carried two rows of characters so the machine could print in two languages or with a large set of special symbols; the University of Amsterdam record documents a 630 ECS/IBM configured for the IBM PC character set and rated at up to 40 characters per second. A companion model, the Diablo 1620, added a keyboard, and Wikipedia notes the print mechanism was also sold to OEMs — resold by Digital Equipment Corporation as the LQP01/LQPSE and by Hewlett-Packard as the 2601A.

Place in printing history

Daisy-wheel printers from Diablo and competitor Qume were, per Wikipedia, the dominant high-end output technology for computing and office-automation applications by 1980, prized for typewriter-quality text. They could not print graphics and were slower and noisier than the dot-matrix, laser, and inkjet technologies that followed, and letter-quality impact printing faded through the 1980s. The 630 is nonetheless well represented in museum collections — including the Computer History Museum and the Smithsonian's National Museum of American History — as a representative example of the letter-quality era, and its command set outlived the hardware through emulation on later printers, including early laser printers such as the original Apple LaserWriter (per Wikipedia).