What is causing such trippy image artifacts? (Presario 1800 + Rage 128) \ VOGONS

What is causing such trippy image artifacts? (Presario 1800 + Rage 128)

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First post, by adalbert

Posted on 2020-10-17, 21:33

adalbert Offline

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Joined: 2014-06-28, 11:40
Location: EU

What is causing such weird image behavior? I got that after running Windows 98 setup.exe off possibly corrupted hard drive on Presario 1800 laptop (P3, ATI Rage 128).

The system obviously has frozen, but instead of rebooting or getting a black screen, the screen just began displaying more and more of different, random colors and artifacts. This is not the first time I see this, I also saw similar behavior on different hardware.
What causes that quite fascinating phenomenon (technical-wise)? Is it caused by noise getting into video memory of frozen video card, or something like that? Or maybe the memory is not being refreshed and is discharging?

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Repair/electronic stuff videos: https://www.youtube.com/c/adalbertfix
ISA Wi-fi + USB in T3200SXC: https://www.youtube.com/watch?v=WX30t3lYezs
GUI programming for Windows 3.11 (the easy way): https://www.youtube.com/watch?v=d6L272OApVg

Reply 1 of 1, by mkarcher

Posted on 2020-10-17, 21:42

mkarcher Offline

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Joined: 2019-01-19, 16:29
Location: Germany

This looks like the BIOS or the windows setup program misprograms the graphics chip in a way that the backlight is still active, but the LCD no longer gets refreshed. The animation (at least up to the point where the screen is full white) is very typical for the "discharge process" when LCDs stop getting the image refreshed. The pattern is quite unknown because software usually takes care to disable the backlight before stopping data refresh, so the pattern is invisible due to missing backlight. In case of your system, the windows setup program is most likely corrupted in a way that it corrupts the graphics controller settings to cause LCD refresh to fail.

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