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Horizontal distortion/shimmering on Voodoo Banshee

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First post, by guyjin37

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Got lucky on a Voodoo Banshee fine and love the card way more than I thought I would; fits perfectly in my mid-late 90s K6-2 build. Performs well with no artifacting or other glitches with the exception of the following.

Depending on the resolution and frame rate, there is some subtle but annoying horizontal "shimmering"-like distortion. The only other place I was able to find anybody dealing with it was here about 5 years ago but there was no conclusion: Re: Impossible?

Has anybody seen or dealt with anything like this? Would love to solve it. I would add my own screenshots but the above captures it pretty much perfectly.

With my card I can stop or limit the distortion with certain res/frame rate combos. For example:

- 800x600/75Hz - No distortion
- 800x600/60Hz - light distortion
- 640x480/60 or 75Hz - distortion
- 1024x768/60 or 75Hz - distortion

I can live with keeping my desktop at 800x600/75Hz. But it's pretty distracting while playing 2D games with capped framerates and such. Interestingly, I did not notice the shimmering in any Glide games I've tried (Quake I & II, Tomb Raider).

Just checking whether there have been any others with this issue over the last 5 years. Thank you!

Reply 1 of 3, by rasz_pl

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More and more machines with this exact glitch Horizontally flickering image from video card?
Wonder what is the common factor. What monitor are you using? can you try with another one? Do you happen to have an oscilloscope?

Open Source AT&T Globalyst/NCR/FIC 486-GAC-2 proprietary Cache Module reproduction

Reply 2 of 3, by guyjin37

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rasz_pl wrote on 2024-02-02, 06:23:

More and more machines with this exact glitch Horizontally flickering image from video card?
Wonder what is the common factor. What monitor are you using? can you try with another one? Do you happen to have an oscilloscope?

No oscilloscope handy where I am. Using an LCD LED just as in the post you referenced actually. With some of the hints there in that thread I was able to overcome some of my issues. Here's how:

Using the monitor's auto-adjust on a per-game or per-screen basis, it would set the phase and control just right most of the time, eliminating the issue for the current task. Occasionally I'd have to adjust either the phase or control or both to eliminate the last little wobbles. When I get back to desktop or command line I'd then have to reset it.

Before using an s3 Trio64+ and a Voodoo1, and then putting in a geforce2 mx400 PCI for testing I saw none of this with the same monitor. I guess it's specific to the card or type of card without anything else available to test.

I am happy that there is a solution even if it requires constant tending to. I'd use a CRT but in my small Japanese house it's just not feasible to keep one around.

Thanks for linking that post! Hope it provides solutions for others.

Reply 3 of 3, by rasz_pl

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guyjin37 wrote on 2024-02-02, 13:51:

Using an LCD LED just as in the post you referenced actually.

What brand and model?

guyjin37 wrote on 2024-02-02, 13:51:

Using the monitor's auto-adjust on a per-game or per-screen basis, it would set the phase and control just right most of the time, eliminating the issue for the current task. Occasionally I'd have to adjust either the phase or control or both to eliminate the last little wobbles. When I get back to desktop or command line I'd then have to reset it.

Auto-adjust settings should be saved per display mode and saved individually.

Open Source AT&T Globalyst/NCR/FIC 486-GAC-2 proprietary Cache Module reproduction

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