Hewlett-Packard  LaserJet III - 33449

GENERAL INFORMATION

The Resolution Enhancement Technology (RET) introduced with the HP LaserJet  III represents a technical milestone in the history of desktop laser printers.  RET eliminates the fine stair steps normally seen on diagonal lines from  printers with conventional 300 dpi controllers. RET uses variable dot sizes to smooth jagged lines and edges on all types of text and graphics. It also sharpens corners and intersections by placing smaller dots at the pointed tips. The result is print quality that has the sharpness of 600 dpi on the edges.

The LaserJet III also introduced the PCL 5 printing language with enhanced page formatting features. PCL 5 is a superset of PCL 4, which is built into  other LaserJets. It provides the LaserJet III with much of the functionality of  PostScript without the cost and processor overhead. All older PCL 4 applications  should print perfectly with PCL 5. HP also integrated its industry standard  HP-GL/2 pen plotter language into PCL 5. HP-GL/2 allows graphics to be described very efficiently and many CAD applications require it. Older LaserJet II printers required PDP's Plotter-in-a-Cartridge product to emulate HP-GL/2.

PCL 5 was conceived as a substitute for PostScript much in the same way Canon  developed CaPSL. A major shortcoming of CaPSL is that it's a dead-end for higher  print quality; there are no typesetters that use CaPSL. Most publishers using PostScript use low-cost 300-dpi laser output for drafts and then print to PostScript-equipped image setters, such as a Linotronic machine, for the final film.

This exact correspondence between low cost proof copies and typeset-quality  camera-ready copies has been one of the key ingredients for the phenomenal success of PostScript and its creator, Adobe Systems, Inc. HP realized that in  order for PCL 5 to be a substitute for PostScript, there had to be high resolution typesetting equipment compatible with PCL 5. So HP teamed up with CompuGraphic to use CG's Intellifont type fonts and scaling technology as part of PCL 5. Together they wrote a program called DirectSet that translates PCL 5 commands into code for the AGFA Compugraphic Series 9000 imagesetters.

To hedge its bets, HP also contracted with Adobe to provide a PostScript cartridge for the LaserJet III. Resolution Enhancement Technology works well in  the PostScript mode, but you should disable RET when printing scanned images because the dots added by the RET circuitry to smooth the image tend to reduce  clarity. The LaserJet III allows the operator to turn off RET from the control  panel. The LaserJet III sold far better than expected and was in short supply during all of 1990. The III was HP's third grand slam in the printer business and is one of the most popular printers on the market.

On October 26, 1992 Hewlett Packard bombed the laser printer industry with the much anticipated introduction of the LaserJet 4 and LaserJet 4M. These  reasonably low-cost 8 ppm printers are based on the new Canon P-270 engine (also called EX), which provides true 600 dpi by way of new ultra-fine toner technology. EX printers are smaller than the SX/TX, with both a 75 sheet multipurpose tray and a 250 sheet cassette as standard and a third cassette (500 sheet) as optional. Hewlett-Packard killed the LaserJet III and critically  wounded every other OEM of the SX engine. It was a sad, but inevitable, day for  the SX engine. Four months later, in February 1993, Canon sent letters to all SX  OEMs announcing the last chance to place orders for SX and TX engines as production would end by 1994. The RX engine remained in production until a duplex printing option was created for the revised LaserJet 4, called the  LaserJet 4 Plus.

FONT INFORMATION

PCL 5 works with scalable fonts and the LaserJet III includes 8 scalable typefaces (the CG Times and Univers families). CG Times is like Times-Roman, and Univers is very much like Helvetica. These two faces are provided in normal,  bold, italic, and bold italic. Type can be scaled in quarter-point increments from .25 up to 999.75 points. Bitmapped Courier and line printer fonts are also  included, as are 35 internal symbol sets.

Controller Notes

Like the IID controller, the LaserJet III controller was designed and built  by HP rather than Canon. The boards are made in the U.S.A. (Boise, Idaho) and then sent to Japan for integration into the printers. Three major revisions of the circuit board exist. The part numbers are: 33449-60001, 33451-60001, 33497-60001. HP uses the suffix 69001 instead of 60001 to label boards that have been "restored" by their repair facility and sold as replacement parts.

The early revision boards used many small surface-mount chips and five large 40-pin masked ROMs for the firmware. The new boards have all the functions of the small chips integrated into a few large Application Specific Integrated  Circuits (ASICs), and the firmware is placed in four small surface-mount masked ROMs. A picture of the original version HP III controller is shown above. The  latest version, with its large ASICs, is shown in the next section, covering the LaserJet IIID.

HP's investment in custom surface-mount chips allows it to produce high-quality controllers that are extremely reliable at a fraction of the cost of the original LaserJet and LaserJet II controllers. HP engineers have created the highest ratio of controller performance to build cost in the industry. This  technological edge allows HP to sell printers at competitive prices and still  enjoy a healthy profit margin.

The controller contains an ASIC for RET. This special chip scans multiple  raster lines and generates different sized dots to eliminate the "jaggies" on diagonals and curves, sharpen the tips of points, and clean up the inside  corners of line intersections. All this results in better looking print which,  at its best, can approach the output of 600 dpi controllers.

One of the beauties of RET is that it improves print quality without increasing RAM requirements or degrading print speed. Since PCL is basically a  300 dpi protocol, it was important for HP to figure out a way to improve print quality without losing compatibility with 300-dpi font and graphic data. Another advantage is that RET acts independently of the controller's native language,  yielding enhanced output whether the original bitmap was created by PCL 5,  PostScript, or any other process.

Another nice feature of the LaserJet III controller design is that it can  plug into a LaserJet II and effectively turn the older printer into a LaserJet III. This upgrade can be made without changing anything else, since the  mechanical design is identical. Although the control panels look different, they  are functionally identical. It's a pleasant surprise to see a faithful old LaserJet Series II produce beautiful resolution-enhanced output after a new LaserJet III controller board has been installed!

Standard memory is 1 megabyte and two slots are provided to add up to 4  additional megabytes. HP was criticized for providing non-expandable memory boards for the LaserJet II and IID. Memory cards from HP are still not  expandable, but HP included a second slot in the III so that you don't have to  discard your old card when you add memory to a printer that already has a card installed. HP does not make a 4 megabyte memory card for the LaserJet III.

The optional video interface does not work with products such as the JetScript Adapter, but it works fine with interface cards that merely use the  video lines (e.g., the LaserMaster). The LaserJet III uses the same RAM cards as  the IID and the IIP, but it has two slots instead of one. These cards are different from those used with the Series II.

LaserJet III and IIID Use the Same Controllers

All versions of the  LaserJet III controller will function perfectly as either a LaserJet III or a LaserJet IIID controller! HP shrewdly programmed the LaserJet III controller to  sense the engine type and operate accordingly. As a result, service facilities need only stock one type of controller to support both LaserJet III and IIID  printers.