------------------------------------ MORTON'S MUSINGS: Choosing a Monitor By Morton A. Kevelson ------------------------------------ WHAT YOU GET IS WHAT YOU SEE Choosing a video monitor display for the Amiga used to be relatively simple. You started with an Amiga 1000 and bought the Amiga 1080 monitor with it. The proper cable was supplied by Commodore. You connected the computer to the monitor and were up and running. That was it. With the advent of the Amiga 2000, things started to get complicated. The Amiga 2000 is equipped with a dedicated video slot which many developers felt obligated to fill. The most fundamental accessories for the video slot are de-interlacer boards, such as the flickerFixer or the Amiga 2320, which eliminate the annoying flicker when the Amiga is using its interlaced display mode. The Amiga 1080 monitor, or the 1084 which is the current model, cannot display the de-interlaced output. Recent advances in Amiga hardware have changed the picture once again. The Amiga 3000 has a built-in de-interlacer, as well as the Enhanced Chip Set or ECS. The ECS is also available for retrofit into existing Amiga computers. With the release of AmigaDOS 2.0, the new hardware display modes can be easily accessed on any system. To accommodate the new display modes, Commodore has added several video monitors to its product line. In particular, the Amiga 1950 display monitor can accommodate all the ECS'ES and the Amiga 3000's new display modes. The Amiga 1950 has recently been replaced by the Amiga 1960. More on this later. Having just gone through the process of updating the video display system of my Amiga 2000, I feel the information will be of use to the readers of this column. For Amiga 500 and Amiga 2000 users, the ECS consists of two chips: ECS Agnus and ECS Denise. There are several versions of ECS Agnus. All Amiga 2000's, since about 1988, and more recently Amiga 500's as well, have been equipped with the first version of ECS Agnus, which has also been known as the Fatter, Obese or Super Agnus. This ECS Agnus, chip number 8372A, is able to access one megabyte of chip RAM. The 8372A can also be soft-switched between the NTSC and PAL display modes. Amiga 2000's with the 8372A installed were configured at the factory for one megabyte of chip RAM. Amiga 500's with the 8372A installed are sold with only 512 kilobytes of chip RAM. Amiga 500s with the 8372A can be upgraded to one megabyte of chip RAM by installing a 512 kilobyte RAM expander in the computer's belly slot and changing some printed circuit jumpers on the mother board. At this writing Commodore still officially frowns upon the modifications which convert an Amiga 500 to one megabyte of chip RAM. This attitude may change with the official release of the Amiga 500 CDTV attachment, since many CDTV titles require one megabyte of chip RAM to run. The 8372B is the version of ECS Agnus supplied with the Amiga 3000. The 8372B differs from the 8372A in that it can access two megabytes of chip RAM. The Amiga 2000/500 can be upgraded to the 8372B by the addition of circuit board that includes the 8372B along with an additional megabyte of RAM and the appropriate circuitry. The MegAChip board from DKB Software does the job. I have a MegAChip 2000 in my Amiga 2000. The latest version of the MegAChip board is about a third the size of the original release and can be installed in both the Amiga 500 and the Amiga 2000. Other than the ability to switch between NTSC and PAL display modes, ECS Agnus does not offer other display enhancements. I previously mentioned the Amiga 1080/1084 monitors are capable of working with both NTSC and PAL video. On the 1080, a screwdriver adjustment on the back panel of the monitor will compensate for the difference in height between the NTSC and PAL display modes. ECS Denise, chip number 8373, offers several potentially useful new display modes. The SuperHires and Productivity display modes offer increased resolution, as well as a de-interlaced, flicker-free display. The tradeoff is that the higher resolution display modes can only display four colors out of a palette of 16. Since ECS Denise is pin-compatible with the old Denise, its installation does not require any modification of the computer other than a chip swap. Its replacement is relatively simple, as a DIP chip can be pried out with a small screwdriver. ECS Denise sells for less than $50 and it returns much for little investment. The catch is that in order to utilize the de-interlaced display modes, you will have to replace your trusty 1080/1084 monitor with something better. The following table summarizes the video hardware display modes and the resulting screen sizes in pixels without overscan that the Amiga can generate if both the ECS Agnus and ECS Denise have been installed: Display Mode NTSC PAL Colors Lores 320 x 200 320 x 256 32 or 64 in extra halfbright Lores interlaced 320 x 400 320 x 512 32 or 64 in extra halfbright Hires 640 x 200 640 x 256 16 Hires interlaced 640 x 400 640 x 512 16 SuperHires 1280 x 200 1280 x 256 4 out of 64 SuperHires interlaced 1280 x 400 1280 x 512 4 out of 64 Productivity 640 x 480 4 out of 64 Productivity interlaced 640 x 960 4 out of 64 Note that the productivity modes are neither NTSC nor PAL. All but the Productivity modes can be viewed on the Amiga 1080/1084 monitors. The only other limitation of the 1080/1084 monitors is that by today's standards, their resolution -- dot pitch -- could be better. To view the Productivity modes requires a monitor with a raster scan rate of 31.46 KHZ. This brings us to the second part of this discussion: choosing a suitable monitor. The type of monitor needed is determined by the structure of the video display. All the video displays encountered with the Amiga are raster scan displays. That is, the images are built up by the rapid scanning of horizontal parallel lines by an electron beam across the face of a phosphor- coated glass picture tube. As the electron beam strikes the phosphors, they radiate visible light in one of three colors: red, green or blue. When the electron beam has scanned enough lines from top to bottom to completely cover the face of the tube, it is rapidly returned to the top to repeat the process. Two parameters determine the characteristics of the display. The raster scan rate is the number of horizontal sweeps the electron beam performs in one second. For an NTSC display this number is 15,734 scans per second or 15.734 KHz. For a PAL display the raster scan rate is slightly less at 15.625 KHz. The Productivity mode's raster scan rate is double that of the NTSC rate. The second parameter describes the rate at which the electron beam moves from top to bottom. This corresponds to the number of images painted on the screen every second. For NTSC and Productivity modes the vertical refresh rate is 60 fields per second or 60 Hz. For the PAL mode it is 50 Hz. The slower PAL rate is why North American residents may perceive a slight flicker on European television sets. To display more than one video mode, a monitor has to be able to switch between the various scanning rates. Most television sets and computer monitors can operate at only one scanning rate. Various terms are used to describe monitors which can switch between scanning rates. Multiscanning, variable scanning, variable synchronizing, autosynchronizing and multisync are typical examples. The last example is a trademark NEC. I have already mentioned the Amiga 1080 and 1084 monitors are capable of automatically switching between the NTSC and PAL modes. However, to view all the ECS modes requires a monitor that can handle raster scan rates of 15.625 KHz, 15.734 KHz and 31.468 KHz with vertical refresh rates of 50 Hz and 60 Hz. If the Amiga is equipped with a de-interlacer board, then a raster scan rate of 31.24 KHz corresponds to the PAL display mode. The obvious choices are the Amiga 1950 or 1960 monitors from Commodore. These monitors can handle all of the Amiga's display modes and are supplied with the appropriate cables and adapters. The difference between the 1950 and the 1960 is the in the layout of the controls and the dot pitch of the CRT. The 1950 has a dot pitch of .31 mm, while the 1950's dot pitch is slightly better at .28 mm. A monitor's dot pitch determines the maximum resolution of the display. Color monitor screens are actually coated with three different phosphors that emit either red, green or blue light when they are struck by the electron beam; hence the origin of the RGB display. To create white light, all three phosphors must glow. The phosphors are arranged as triads of nearly microscopic dots. The dot pitch specifies the spacing between dot triads in millimeters. A dot pitch of 0.31 mm, which is that of the 1950, corresponds to a screen resolution of about 82 dots per inch. A dot pitch of 0.28 mm, which is that of the 1960, translates to about 91 dots per inch. Thus, a monitor with an active display width of 11 inches and a 0.28 mm dot pitch can resolve a maximum of 1001 dots on a single scan line. If your Amiga is equipped with a de-interlacer board and you intend to work with only the NTSC display modes or the Productivity mode, the best monitor buy would be a standard VGA unit with a .28 dot pitch CRT. These are currently selling for little more than $300. PRINCETON ULTRA 1400 MONITOR REVIEWED When I started looking for a variable scanning rate monitor, I reasoned I should be able to find a 14-inch unit for less than $400. I rejected the 1950 since I was interested in a CRT with no more than a .28 mm dot pitch. Monitors with a .25 mm dot pitch are available but still command at least a $200 premium over a correspondingly sized .28 mm monitor. After shopping around, I settled on the Princeton Graphic Systems model Ultra 1400 which I purchased from Damark International for $399 plus shipping. The Ultra 1400 has an impressive set of specifications. Its nominal 14 diagonal, .28 mm , CRT has and active diagonal that measures 13.25 inches. It monitor automatically synchronizes with raster scan rates over a continuous range of 15 KHz to 36.5 KHz and vertical refresh rates from 45 Hz to 120 Hz. This means the Ultra 1400 can handle any video signal my A2320 equipped Amiga 2000 can send to it. The controls on the Ultra 1400, which are all located on the front panel, are well suited to the Amiga. It has four separate controls for adjusting both the horizontal and vertical size and position, as well as contrast and brightness controls. An OVER/UNDERSCAN button, which is designed to accommodate the IBM CGA display mode, works well with the bypass switch on the A2320. This allows the screen to be completely filled, without any black borders, for all display modes. Conversely, the OVER/UNDERscan button can be used to view all of an overscan image at once. A TEXT button cycles the display between full color, and three monochrome modes, one blue and two green. The Ultra 1400 comes with a detachable connector cable that fits the 15- pin VGA style connector on the A2320. The Ultra 1400 can be connected directly to the Amiga's 23-pin video port with a proper adapter. If this is done, the Productivity mode can be used to provide a flicker-free, de- interlaced display without installing a de-interlacer board. The square aspect ratio of the Productivity mode's pixel is excellent for use in page layout and structured drawing applications. The adapter also must provide for the electronic inversion of the Amiga's horizontal and vertical synchronization signals. Commodore part number 390682-01 will do the job. It is supplied with the A1950 and A1960 monitors. If you are interested in building the adapter yourself, send me a self-addressed stamped envelope and I will provide a schematic and parts list. I have tested the Ultra 1400 with every possible display mode that can be generated by an Amiga 2000 equipped with the ECS chip set and an A2320. The monitor was even able to handle the 640-by-960 pixel Productivity interlaced mode without any problems. In all modes, including the SuperHires interlaced 1280 x 512 pixel PAL mode, the text on the Workbench screen was quite readable while using the default AmigaDOS 2.04 fonts. I was pleasantly surprised by this degree of resolution. My own calculations show that a monitor with these specifications should not be able to differentiate every pixel of the SuperHires interlaced display. If you do switch from an Amiga 1080/1084 monitor to either the Ultra 1400 or the A1960, you should be prepared to give up two features: a built-in audio amplifier/loudspeaker and a composite video input. AMIGA 2320 REVIEWED The A2320 is a plug-in card that fits the Amiga 2000 video expansion slot. The video expansion slot is located to the right of the Amiga 2000's power supply as seen from the front of the computer. To install the A2320, remove the two screws holding the plate at the rear of the video slot, insert the A2320 and anchor it with the pair of screws. The A2320 is fitted with a standard DB15, VGA-style connector located on the rear mounting bracket. Also on this bracket is a small toggle switch that places the A2320 into bypass mode and an access hole for the A2320's fine tuning adjustment. The A2320's coarse tuning adjustment can be accessed only with the computer's cover removed. It should not be necessary to access the coarse tuning adjustment. In normal operation the A2320 doubles the raster scan rate of the Amiga's video signal. A variable scan rate monitor is required to utilize this. If you are able to limit your operation of the Amiga to its NTSC display modes and never place the A2320 in bypass mode, you may be able to get by with a lower cost VGA monitor. Connection is only to the VGA connector on the A2320. The 23-pin video connector on the Amiga will not be required except for use with a genlock. For the latter application the composite genlocked signal will be displayed on a separate video monitor, while the A2320 will continue to display the Amiga's video output on its own monitor. The A2320 doubles the raster scan rate of the Amiga's video output by digitally storing one field of each video frame. When the second field is generated, the A2320 transmits the first field by alternating its scan lines with that of the second. If the original display mode is non-interlaced, as for a 200-line image, or 256-line image for PAL systems, the resulting image appears to be completely filled in. If the original image is interlaced, as for a 400-line image or 512-line image for PAL, the resulting image will be de-interlaced, eliminating the apparent flicker normally perceived on the 1080/1084 monitor. If the A2320 receives a video format it cannot handle, it automatically switches into bypass mode and sends the signal through unaltered. At this time the only display modes the Amiga will generate to switch the A2320 into bypass mode are the Productivity modes. The second limitation on the operation of the A2320 are the new SuperHires display modes. The bandwidth and size of the frame store on the A2320 limits its operation to the transmittal of every other pixel when dealing with the SuperHires display modes. This can distort the display to some extent. For example, the vertical lines of some windows may simply disappear. Of course the undistorted display can be quickly restored by flicking the bypass switch and giving up the de-interlacing feature. FONTS GALORE The latest release of Gold Disk's premier page layout or desktop publishing package, Professional Page 3.0, includes FontManager, a very useful little utility. It converts Adobe Type 1 fonts into the Compugraphic format font that Professional Page can use. I have been using FontManager and find it works within certain limitations. It will convert any Adobe Type 1 font to Compugraphic format as long as it is not too complex. What is too complex? Unfortunately, the only way I know of finding out is by trying to do it. FontManager starts cogitating the Type 1 font happily enough until it pauses in mid-stride. At this point it is impossible to do anything with FontManager short of rebooting the computer. Fortunately, the system does not crash, so you can just shove FontManager aside and get on with other things. FontManager does work well with the fonts it can handle. It has a nifty preview mode which lets you preview the font by way of the classic "quick brown fox..." phrase prior to converting it. Oddly enough, FontManager is able to preview the fonts on which it chokes during a conversion attempt. Gold Disk is aware of FontManager's limitations and hopes to have a fix ready with the next update of Professional Page. I'M OPEN TO FEEDBACK If you have any comments or suggestions regarding this column, or if you have some particular topic you would like to discuss, then drop me a note. I normally do not respond directly to individual requests, but I promise to read everything you submit. Here is the address: Morton Kevelson P.O. Box 336 Cooper Station New York, NY 10276-0336 DEVELOPERS MENTIONED Princeton Graphics Systems 1100 Northmeadow Parkway Suite 150 Roswell, GA 30076 800-227-1490 or Norfolk House GT. Chesterford Ct. GT. Chesterford Saffron Walden, Essex CB 101PF England (44)0799 30963 Gold Disk 5155 Spectrum Way Unit 5 Mississauga, Ontario Canada L4W 5A1 416-602-4000 800-465-3375 Commodore Business Machines 1200 Wilson Drive West Chester, PA 19380 215-431-9100 DKB Software 50240 W. Pontiac Tr. Wixom, MI 48393 313-960-8750 END OF TEXT