![]() ![]() In response, VESA established a standardized list of display resolutions, refresh rates, and accompanying timing for hardware manufacturers. A monitor capable of displaying at both resolutions would need to be able to horizontally scan in a range from at least 31 to 68 kHz. In addition to these higher resolutions and frequencies, during system boot on systems like the IBM PC, the display would operate at standard low resolution, such as the PC standard of 720x400 at 70 Hz. the IBM market began to develop Super VGA cards which used many different scan rates, culminating in the VBE which established standardized methods for outputting many different resolutions from one card, eventually becoming the Generalized Timing Formula which permitted graphics cards to output arbitrary resolutions.īy the late 1990s, graphics cards for microcomputers were available with specs ranging from 1024x768 at 60 Hz, to at least 1600x1200 at 85 Hz. Many different display formats for Macintosh, Sun, NeXT, and other microcomputersĪfter 1987's VGA. ![]() XGA: 35.5 kHz horizontal scan, 87 Hz (43.5 Hz interlaced) vertical scan (plus VGA modes).CGA/EGA resolutions are transmitted to the monitor at VGA compatible timings. VGA: 31.5 kHz horizontal scan, 60 or 70 Hz vertical scan.EGA: 15.7 kHz (CGA compatible mode) or 21.8 kHz horizontal scan, 60 Hz vertical scan.PAL, NTSC, CGA: ~15.7 kHz horizontal scan, 50 or 60 Hz vertical scan.At this point, PC and Mac owners with multiple graphics cards required unique monitors for each of them, and by the late 80s all of the below computer video standards required monitors which supported a small number of specific frequencies: IBM's 1987 VGA standard, in turn, expanded to three fixed scan rates. The NEC Multisync was released in 1985 for use with the IBM PC, supporting a wide range of sync frequencies including those for CGA, EGA, various extended forms of those standards marketed by third party vendors, and standards yet to be released. This monitor as well as others that could be manually switched between these two sync rates were known as dual-scan displays. In 1984, IBM's EGA added a second resolution which necessitated the use of a monitor supporting two scan rates, the original CGA rate as well as a second scan rate for the new video modes. Early Macintosh monitors also used fixed scan rates. The CGA timings were identical to NTSC television, whereas the MDA card used a custom timing for higher resolution to provide better text quality. IBM's original 1981 PC, for instance, was sold with a choice of two video cards ( MDA and CGA) which were intended for use with custom IBM monitors which still used fixed scan rates. ![]() These display standards had fixed scan rates, and only used the vertical and horizontal sync pulses embedded in the video signals to ensure synchronization, not to set the actual scan rates.Įarly dedicated computer monitors still often relied on fixed scan rates. Computers History Įarly home computers output video to ordinary televisions or composite monitors, utilizing television display standards such as NTSC, PAL or SECAM. "MultiSync" specifically was a trademark of one of NEC's first multiple-sync monitors. Multiscan computer monitors appeared during the mid 1980s, offering flexibility as computer video hardware shifted from producing a single fixed scan rate to multiple possible scan rates. They are generally used for computer displays, but sometimes for television, and the terminology is mostly applied to CRT displays although the concept applies to other technologies. ![]() In contrast, fixed frequency monitors can only synchronise with a specific set of scan rates.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |