Inter-Office MemorandumToHarold HallDateApril 6, 1981Lynn ConwayVLSI Systems Design AreaFromRich PascoLocationPalo AltoSubjectColor Printer/PlottersOrganizationPARC VLSI Systems DesignXEROX Filed on: [Indigo]RamtekPlotter>Printers.Bravo, .PressIntroductionThis report summarizes an investigation into color plotting devices appropriate for producingcheckplots of VLSI circuit layouts. The goals of the investigation were to find a plotter optimizedfor low cost and reliability.Types of Printer/PlottersImpact. Like a typewriter, hammers push an inky ribbon against paper, with one hammer blow perpixel. These machines are simple in concept. The major drawback to impact printers is thatribbons need frequent replacing. Also, there are many moving parts subject to breakage and wear.In the Ramtek 4100, there are four heads, each with a different colored ribbon, mounted on a singlecarriage which travels horizontally across the entire paper, marking eight rows of pixels (or one lineof characters) at a time. Each head has eight hammers arranged vertically. It is possible to replaceonly one color ribbon, should it be used before the others.In the Trilog ColorPlot, there are 44 hammers spaced horizontally about one-third inch apart acrossthe 15" page, mounted on a carriage which shuttles about one-third inch back and forth. Firstevery N-th dot in each line is printed, then the dots in between as the head moves. The paperadvances one line and the process repeats. The ribbon has three sections spliced end-to-end, onefor each primary color. A separate pass over the drawing is made for each color, with the ribbonsrewound or fast forwarded in between.Inkjet. A fine stream of liquid ink is squirted from a nozzle and deflected electrostatically betweenthe paper and a gutter. Variations include: Whether the jets squirt onto a drum which transfers theimage to the paper, or directly onto the paper. Whether the surplus ink in the gutter is recycled ordiscarded. How many jets and how they are arranged. The Applicon device produces beautifulplots on single sheets up to 34" wide, but its $40,000 price places it out of our reach. ThePrintaColor IS8001 sells for $6,000, but its sample printouts are of uneven dot size, relatively poorregistration, and inaccurate color rendition. Ink jet printers are reputedly prone to jet clogging; nottoo reliable.Xerographic. An electrostatic charge is placed on a photosensitive drum, and a mechanicallydeflected laser writes an image, discharging the drum where it writes. Powdery toner is dusted overthe drum, sticking where charge remains. Then the toner image is transferred to paper. Theprocess is repeated for each of three primary colors, then the paper is heated to melt the toner andfuse it to the paper. Only known manufacturer is Xerox; plotter is based on 6500 copier; plottersknown as Puffin, Pimlico, and CGP (color graphics printer). The latter is a Xerox product; othersare research prototypes.]gpi c8q]rX -q7Br ]a ]`0 ]q]r -q7Br Yq]r-q 7BrSsr M: Gp D}r2+ BH Au >pi :tr1( 9T$9 7': 45. 3 .8 1[ 0; ,"A +iW )L (`I &b %X% "-trM I %] *2 Y ,9 S  et rQ >& ]D ` UY 11 M  =]3Color Printer/Plotters2Electrostatic. Paper passes over an array of metal nibs which impart an electrostatic charge whereprinting is desired. The paper is next washed by a toner bath containing colored toner particles,which adhere to the static charge. Versatec and others make black-and-white printer/plotters; nocolor machine is known.Thermal Dye Transfer. Paper is brought in contact with a web of special paper coated with a waxyink as it passes over a head containing several hundred resistors. Spot heating causes the wax tomelt and the ink to transfer to the paper. Fuji Xerox makes a black-and-white version; no knownmfrs. of color version, which would require three print-head/web-transport assemblies.Considerations when selecting a printer(reliability, serviceability, etc.).A more global view of our decision is not which commercial color printer to buy so much as howcan we meet our color printing needs. A major advantage of using a Xerox color printer (e.g. Lilac)is the positive impression made on visitors. No printer manufactured outside would speak as highlyfor Xerox.Ribbon Cost. One drawback for impact printers is the cost of replacing the inked ribbon. TheTrilog 3-color ribbon costs $40; the Ramtek uses four colored ribbon cartridges at $10 each.Ribbon life seems to be comparable for both machines, between several dozen and several hundredplots, depending on the density of the plot and the allowable fading. Presently, for either machinethe ribbon must be replaced when its ink is depleted, but Ramtek promises to release a re-inkingcartridge, which would allow a ribbon to be used as long as the fabric lasts.SoftwareOne issue in considering whether to buy a color printer is the amount of programming which wouldbe required on our part. Should it run Press? Or should a special program to do LSI plotting beused? Who is to write output module to drive the new printer? It appears that several person-months of programming would be required.Press (the program) could be modified to drive an impact printer. Then Press files from arbitrarysources (e.g. Sil, Griffin) could then be printed. One major drawback to using Press is that thepage length (hence aspect ratio) is set to a constant when Press is installed. It would thus bedifficult to produce drawings of arbitrary height. Since Press delivers three single-color bitmaps onthree passes, Press might be easier to interface to the Trilog than to the Ramtek.Alternatively, a new output module could be added to the Jam CIF processing software. Thiswould bypass the Press file format and its restrictions, eliminate the necessity of BCPL modificationsto the Press program, and permit direct control of the plotter from the LSI plotting software (thusfacilitating dedicated stipples, integral numbers of printer dots per lambda, etc). The disadvantageis the inability to print Press files from other sources (e.g. Sil, Griffin). Since the Jam colorplotting routines represent color on a pixel-by-pixel basis, the interface here to the Ramtek might beeasier.Perhaps some amount of software can be imported, although this is not likely to be too useful. Forexample, Bart Locanthes's CIF plotting program (see appendix) could be imported and translatedfrom C'' to Mesa.Halftoning: image resolution vs. color menu. Halftoning is the process of using variable size dots torepresent different intensities of each primary color. Most printers are not directly capable ofhalftoning; they make a binary decision for each primary color (strike or don't strike) on each dot.To produce a halftoned image on such a printer, the printer resolution must be much finer than thepicture resolution, so that groups of printer dots may represent each picture element. Withouthalftoning (one picture element per printer dot) only seven colors plus white are available, frG bt r*+ `Q _R ] ZftrA XK W^*6 UV Rhpi' O=r$ LL J;) I T G DZt r9 B= AR5* ?\ >JL <M 9Tp 6(rE 4A 3 $; 1( .qtrX ,7* +i'9 )9- (`R %5)tr #8. "-G A$ %*9 J  V m^  t.r" :': W 2 X E *\ >](_Color Printer/Plotters3depending on whether or not each of the three primary colors is struck. The primary colors usedare yellow, cyan, and magenta; in pairs one obtains red (yellow+magenta), green (yellow+cyan)and blue (cyan+magenta); all three colors at once produces black. But LSI checkplotting requiresmore than seven colors. At a minimum eight colors are required to represent metal (e.g. blue),diffusion (green), polysilicon (red), metal over diffusion (cyan), metal over polysilicon (violet),polysilicon over diffusion (brown), ion implant (yellow), contact cut (black), and overglass cut(brown). Using a 2 x 2 array of printer dots for each halftone dot could in theory produce 63colors (0, 1, 2, or 3 dots turned on in each of three primaries), of which at least eight should beusable. In order that the halftoning pattern is fine compared to the details of the layout, at leasttwo halftone dots or 4 printer dots should be used for each lambda. One such halftone stipple,similar to that used in the sample VLSI printout from Silicon Systems displayed at Group 3Electronics, is shown in Figure 1. Here metal, polysilicon, and diffusion are represented bycheckerboards in cyan, magenta, and green, with the green occupying the opposite polarity of thecheckerboard from the magenta and cyan. Solid outlines help identify the boundaries of each layer.Conclusions and Recommendations:If the CSL xerographic color printer Lilac'' were serviced and maintained regularly, then in manyapplications it would be the printer of choice. When it is properly working it can produce prints ofquality far superior to that obtainable by any other technology. However, the overall cost ofkeeping such a plotter readily available appears to be very high and is not presently provided for.The VLSI Systems Design Area requires access to color plotting at all times. Thus I recommendthat we buy an impact color printer/plotter for internal use as a checkplotting device whendesigning integrated circuits. This machine would provide more reliable service than Lilac, yieldmore legible plots than the black-and-white Versatec, and facilitate the generation of colorwallpaper'' (poster-size plots).Opinions as to whether the Trilog ColorPlot 100 or the Ramtek 4100 is better are nearly evenlysplit. As the appendix shows, users of both machines are happy with their purchase. Bothmachines are approximately the same price, $12,000. The Trilog process is established and reliable,but its multi-pass approach is a bit awkward. The Ramtek process is newer and potentially better,but suffers from minor but annoying design bugs supposedly being fixed. Trilog produces 100 dotsper inch, whereas Ramtek produces 70, but color registration problems with the Trilog limit itspractical resolution to about the same as, or slightly worse than, the Ramtek, which has nearlyperfect registration. Present ribbon costs are comparable, but the advent of the re-inking cartridgewill favor the Ramtek.While either machine would be acceptable, my personal feeling is to favor the Ramtek 4100,because of its better registration, local manufacture, and potentially lower ribbon cost. frG b#= `3* _J ]V \:) Z9' Y6( WP UM Ty6) R? Qq/. OA Ni!B Jpi Gr Y FHS DA C@U @V >? = C ;5' :" 6trt r 5U5% 3Z 2L-5 0K /DJ -&9 ,<[ * 'Nt r & Y d %=BIColor Printer/Plotters4Appendix: User reactionsResponses from Trilog users:Dave DitzelBell Labs, Murray Hill201-582-36553/25/81Has been using Trilog plotter.Quite nice; happy; satisfied.Raster conversion software was fair amount of work.Driven from CIF via program in C'' by Bart Locanthe. Same CIF software is up at CalTech; we couldget a copy if desired.CalTech is also happy with Trilog.When new, would occasionally have 1-2 dots vertical registration error from paper rewind operation,due to controller bugs, now fixed.Better to rewind and change colors after entire drawing. Used to do it after each page, but waiting forribbons to rewind took too long.Misregistration due to tractor-hole elongation not a problem.Ribbon life: 24-hour/day use, 1 day; normal use, 1 week.Resolution: At one dot per line width (2 l), can fit 1000 l per page and still verify connectivity. Don'tusually do DRC by inspecting plots. Plotted 32-bit adder with carry lookahead on 1/2 page.Best to convert entire file to raster first; can take 7000 disk pages of 1 kB each.Don't know about Ramtek printer (didn't look at it when shopping).They're doing M&C courses at BTL-MH, chips fabbed at BTL-Allentown.Steve Johnson of BTL will describe their design environment at Computer Systems Seminar, April 2,1981, 3:30 p.m. Cory Hall, UC Berkeley.Bruce HuntSRIVBH.TSCA @ SRI-UNIX(415) 326-6200 x57133/26/81Using Trilog ColorPlot since early December 1980.Intended use for VLSI checkplots, but software not written yet.Have used it extensively for line-printer & simple plotting.Super-reliable, never failed, zero problems, good quality.Registration is not super-hot publication quality, but OK for in-house use. (Can see mis-registration ifyou use a magnifying glass.)Biggest drawback is standing around waiting for ribbon to rewind to next color.Didn't look at Ramtek; was not aware of it while shopping.Mike WimbrowSilicon Systems714-731-7110 x4033/26/81Had Trilog ColorPlot up since December 1979.No major failures (only a few dirty board edge contacts).Generally quite reliable.Need to use good, heavy paper so solid color areas don't wear through & tear.Need to be sure upper and lower tractors are properly aligned.Paper rewinding: no special handling needed for plots up to 6 ft. long (just let it fall on the floor).Registration is good enough in 6-foot plot for black standard-height text made by superimposing allthree colors.Slower than Versatec; we use Versatec for quick checkplots, Trilog for final going-over. frG api ^e [:tX Y X2r V Str R" P3 OdM L" JcI " GhF D}= B8 Au*urur/?[ >mS )g c X U<]Color Printer/Plotters5Bart LocantheBell Labs & CalTech201-582-73293/26/81Trilog is nice device; no complaints with hardware design.Trilog reps at New Jersey didn't know what they were doing, plugged Unibus interface cards in upsidedown, blew out backplane.Two ways of doing CIF-to-raster scan conversion:Icarus/Versatec way (slow, but doesn't need much memory): For each scan line, see whatitems intersect it, and put them on scan line.Locanthe CIF/Trilog way (fast, but needs a lot of memory):Set up big bitmap for entire plot, then instantiate CIF; BitBlt everything into bitmap asit's found. Requires ~256 kB per page. No problem on VAX with 4 MB main memory;for Alto would need virtual memory on disk, would slow things down. Takes ~3 min.per page on VAX, including running printer.CIF plotting code is available in C'', developed at Bell Labs by Locanthe, brought up unofficially'' atCalTech; would require formal release for Xerox, probably not a problem. CIF parser inYACC, scan conversion ~600 lines of C''.Responses from Ramtek users:Henry FuchsNorth Carolina Univ.919-966-46503/26/81We just bought Ramtek printer, serial number 2.Haven't brought it up yet (it arrived damaged, awaiting replacement head).Chose Ramtek over Trilog on design principals; feel 4 heads, 4 ribbons better than rewinding paper andribbons.Also rejected PrintaColor $6k inkjet; output looks bad: wrong colors, poor registration, etc.Ramtek has given us excellent support on our four 9600 color graphics terminals.Danny Cohen has Ramtek, serial number 1.Danny CohenISI213-822-15113/26/81We chose Ramtek because its one-pass approach looks inherently simpler.We were afraid of misregistration problems which might occur with Trilog's three-pass approach.Our software first writes to CRT bitmap, then dumps screen image to printer in one of two ways:(a) One screen pixel maps into one printer dot. Compact plot, but only 8 colors available (incl.white & black).(b) One screen pixel maps into 2x2 printer-dot stipple. Need bigger plot for same resolution,but wider variety of colors available.Contact Vance Tyree for more details. frG btX ` _r ] Z: YdW U0TyWR.Qq:OYNiQLRKa+ IkHYWF* Ccpi @7tX > =/r ; 8tr 7J 5f4 2] 1P /( ,_t * )Wr ' $tr8 #G_ !_ ?b7_& /%N =N#Color Printer/Plotters6Vance TyreeISI213-822-15113/26/81We have Ramtek printer, serial no. 25. Only one other Ramtek in use in Southern California, at TRW.Lots of hardware problems, infant mortality:Lost five pin-driver transistors so far; one printhead is stuck.Lots of minor firmware bugs:Top-of-form position lost when graphics plot overflows a page.Parallel interface does not exactly conform to Centronics standard.Occasionally misaligns one pass left or right of previous by exactly one or two printer dots.Except for third firmware bug above, registration is absolutely superb; far better than Trilog.Ramtek provides excellent support; they seem to know what they're doing; confident they'll fixfirmware bugs soon.Believe design is inherently far superior to Trilog, just needs time to shake bugs out.Ribbons don't last very long (run out of ink after 3 hours continuous plotting) and they're doggoneexpensive ($10 each times 4 colors). Re-inking cartridge will be a welcome relief.Time to plot 512 lines of pixels at two printer dots per pixel (14 5/8" at 70 dots/inch) is about 7 minutes.918 printer dots max. per line.Driver software needs to keep track of when nine printer lines are sent, to initiate printing pass. frG btX ` _r ] Zd Y,W@ UTy>RCQq] O_ Ni^L KaW IcHYS FlEQ Cc C=$cResolutionTime to printInches x InchesManufacturerModel No.Price$4100TechnologyImpact$12,000PrintaColorInk JetIS8001Colors43InterfaceCentronics 8bit ||RS-232CPrimaryWide x High(4-15) x (0-11)$6,00015 x 11AppliconCP 5586/M8Ink Jet3$45,000 (1978)34 x 22127page, min:sec8:30?3:00? "avg"|| Magtape emul.100RamtekDots/InchIn.Per Page375,040.0311080XeroxPuffin384Xerographic8.5 x 11Long Dim.10560:27Lambda [1][1]But only three work on Lilac[2]4 [2][3]Does not include Press formatting time.[3]Alto/SLOTAlto/SLOT0:278.5 x 11XerographicXeroxCGP3100.040.010212Paper SizeAssumes four printer dots per lambda. Assumes printing to edges of paper.TrilogColorPlot 100Impact370(4-15) x (0-11)100.057262.040375Centronics 8bit ||$12,000:vY. 2Y. !VX9X X CY.CX tTvX tTCT9PJ PJ PJ:vXVtTVPJ:WvY. :WtT:WPJ:vY.!VV !VtTCPJ!VPJ9N N NVNCN!VNVN2vX 4;tN2T :WNVPJ9T:vX *X-X.tPJ*PJ*N.N9K KVKK !VK-vV .tK4;K*vY. t@r??VK=fr=f'3vV:WtK :WJ- 4;J-!VJ-J- 9J- J-VJ-VJ-*J-*K.J-!VvY. rt@J9R R RVRT!VRVR*T.T*R.R:WRCR=H,w TIMESROMAN  TIMESROMAN TIMESROMAN LOGO TIMESROMAN HIPPO  HELVETICA HELVETICA  !A'+.rinters.Sil.t s<GPrinters.Press.VJAttorneys.Bravo$.sdY:8RamtekCable.press.['#YYYY|X[WhGXdddddddddddddddddddddddj/1/Printers.pressPasco22-Feb-82 17:25:45 PST/