andrew@ramona.Cary.NC.US (Andrew Ernest) (06/09/91)
When in 800x600 graphics mode, there is a slow-moving line which "moves" from the bottom to the top of the screen image. It isn't really a line; it's a barely-noticeable brightness difference that just travels up the screen and then starts back down and the bottom again. It's like something is slightly out of sync. But other than that, the picture is beautiful. I'm just curious what causes this. Could it be the VGA card's fault? The card is the CompuAdd Hi-Rez card with 1 Meg (TSENG). No moving effect is visable in either 640x480 or 1024x768 mode. Bonus question: is it normal for the screen image to be narrower in 800x600 graphics mode than it is in 640x480 or 1024x768 mode? The latter two have the same width. I compensate when in 800x600 mode by adjusting the horizontal width control. Since some monitors (like NEC) have memory for holding dimension settings, I'm hoping this is normal for multisync monitors. -- Andrew Ernest <andrew@ramona.Cary.NC.US>
antonyc@nntp-server.caltech.edu (Antony Chan) (06/11/91)
andrew@ramona.Cary.NC.US (Andrew Ernest) writes: >Bonus question: is it normal for the screen image to be narrower in >800x600 graphics mode than it is in 640x480 or 1024x768 mode? The >latter two have the same width. I compensate when in 800x600 mode by >adjusting the horizontal width control. Since some monitors (like NEC) >have memory for holding dimension settings, I'm hoping this is normal >for multisync monitors. i'm not sure what causes the bright line, but i think i can guess what the answer to the other question is. last i heard, 800x600 didnt have a standard, but 640x480 and 1024x768 did. the result is that different cards will have different sync frequencies. i determined this one day when a friend and i were swapping video cards (i have a swan and he has a trident) he has a tri-sync, and i have a multi-sync, and the 640x480 and 1024x768 required no adjustment but 800x600 required us to fiddle with the width controls. on his monitor, i believe, we were unable to get the correct width- the frequency was just too far off. on mine, i think, the adjustment also was right at the end when the right size was achieved. fortunately, my card works well with my monitor, and his is fine with his. anyway, we looked at the specs for his card, my card, and his monitor. sure enough, our 800x600 frequencies were much different, his monitor almost matched his card perfectly, and 640x480 and 1024x768 modes had nearly identical freqencies.
andrew@frip.WV.TEK.COM (Andrew Klossner) (06/19/91)
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"When in 800x600 graphics mode, there is a slow-moving line
which "moves" from the bottom to the top of the screen image."
This can be caused by electromagnetic interference from other devices.
Try truning off everything else in the vicinity, or move the computer
to a pristine site (like the middle of a large field, using a long
extension cord).
I once tracked this effect to an old electric blanket located
downstairs from the monitor.
-=- Andrew Klossner (andrew@frip.wv.tek.com)
(uunet!tektronix!frip.WV.TEK!andrew)