gpeterso@sedona.intel.com (Glenn Peterson) (03/22/89)
I would like to know what determines the maximum resolution of a monitor. How do the horizontal and vertical scanning rates, bandwidth, and dot pitch come into play or do they? I have a Mitsubishi 1371A multi scanning monitor with the following specs: Bandwidth : 30Mhz (from a Byte review) Max Resolution: 800 X 560 (Mitsubishi spec) Horizonatal : 15.6-35Khz (Mitsubishi spec) Vertical : 45-75hz (Mitsubishi spec) Dot Pitch : 0.31mm (Mitsubishi spec) I currently have EGA and am looking to upgrade to VGA. The question I have is whether my monitor will handle 800X600 resolution of say the Paradise VGA Plus 16 card. Will I see 800X600 or not? This is a major issue in my purchase plans. I am a windows user and want the max resolution I can get with my current monitor. The 2 cards I am looking at most are : Paradise VGA Plus 16 800X600 windows driver Video 7 Fastwrite 720X540 windows driver Also could someone shed some light on the "800X600 Flicker" issue that I have heard about? What is Video 7's BBS number? Does Paradise have a BBS? Any help, hints, etc. would be greatly appreciated. Glenn Glenn Peterson Intel Corporation gpeterso@sedona.intel.com -------------------------
myers@hpfcdj.HP.COM (Bob Myers) (03/28/89)
>I would like to know what determines the maximum resolution of a >monitor. >How do the horizontal and vertical scanning rates, bandwidth, and >dot pitch come into play or do they? 1. The dot pitch, along with the size of the raster to be displayed, sets an absolute upper limit on the resolution available from a given color CRT (the tube itself). For example, a 19" color CRT with a 0.31 mm dot pitch can display a raster with 1280 pixels across IF the raster is no less than about 397mm wide (0.31mm x 1280). Monochrome CRTs, of course, do not have this problem; here, the absolute limit set by the tube is more the minimum spot size which can be produced. 2. Scanning rates are determined by the desired resolution and vertical refresh rate. Another example: suppose we want to display a 640 x 480 image, with a refresh rate of 60 Hz. This means a 16.7 msec vertical period, total (both displayed image and vertical blanking). Allowing 5% of the vertical period for blanking (a typical value), we are left with 15.86 msec for the displayed image. This is divided among the 480 lines, to find the required horizontal period is 15.86 msec/480 = 33.05 usec, for a horizontal sweep rate of about 30.25 kHz. Note that this is not too far off from the standard 31.5 kHz rate for monitors at this resolution; the difference is due to the fact that the 5% vert. blanking time was a guess. 3. The bandwidth (along with some related specs, namely the rise and fall times as measured at the CRT cathode) limits the horizontal resolution. Continuing with the example above, note that the 33.05 usec horizontal period is also divided between blanking and image; horizontal blanking is typically about 20% of this time, leaving 24.2 usec to be divided among the 640 pixels in a horizontal line. This means that each pixel takes 24.2 usec / 640, or 37.8 nsec, for a dot clock of 1/(37.8 x 10^-9), or 26.44 MHz. For acceptable resolution, the video amplifer bandwidth should be equal to or greater than this value. (Actually, the fastest video signal that can be obtained is half the dot clock - alternating lines on and off - but an amplifier that can only handle half the dot clock will not have sufficient bandwidth to display distinct single vertical lines.) >I have a Mitsubishi 1371A multi scanning monitor with the following >specs: >Bandwidth : 30Mhz (from a Byte review) >Max Resolution: 800 X 560 (Mitsubishi spec) >Horizonatal : 15.6-35Khz (Mitsubishi spec) >Vertical : 45-75hz (Mitsubishi spec) >Dot Pitch : 0.31mm (Mitsubishi spec) You don't give the monitor's size here; assuming that it's at least a 16" tube, the dot pitch is sufficiently fine. As far as the bandwidth is bandwidth is concerned, I'll assume a 60Hz vertical rate, as above, and get a dot clock of 37.89 MHz, and a sweep rate of 37.89 kHz (odd how those worked out!). From this rough guess, I'd say the monitor is marginal for this application - the horizontal sweep is out of the range specified, for one thing. However, remember that this IS a rough guess - check the timing of the card you plan to use with this monitor against the monitor's specs. I suspect, though, that you could find a monitor better suited to this application. >Also could someone shed some light on the "800X600 Flicker" issue >that I have heard about? Flicker is not directly related to resolution; it is a function primarily of refresh rate, although also affected by the phosphor in question, and the brightness of the display and its surroundings. For the typical color application, 60 Hz *non-interlaced* should be considered the minimum for acceptable flicker. Some manufacturers try to get the higher resolutions by running at 60Hz *interlaced*, which means that the entire image is actually refreshed at only 30Hz. This is particularly noticeable on single horizontal lines, etc.. Hope this has helped. Bob Myers KC0EW HP Graphics Tech. Div.| Opinions expressed here are not Ft. Collins, Colorado | those of my employer or any other {the known universe}!hplabs!hpfcla!myers | sentient life-form on this planet.