VOGONS

Return of the Wavy Lines - this time, it's Matrox

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First post, by maximus

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A follow-up to this thread, in which I describe a wavy distortion pattern affecting the VGA output of my Hercules GeForce2 Ultra. I eventually concluded that this was just some kind of design flaw. The GeForce2 Ultra was known to have this problem, and since it's not really that offensive, I decided to just move on and enjoy the otherwise awesome card.

Imagine my surprise, then, when I fired up a Matrox G400 MAX in the same rig and saw EXACTLY the same distortion pattern! Actually, the Matrox seems to have it even worse. Refer to the mock-up from the original thread. It's really, really bad. The GF2 Ultra was still usable, but the Matrox is so bad that it hurts my eyes after a while.

All of this from a card which was known for having the best 2D image quality of them all. What the bloody hell is going on here?

I've ruled out the following potential causes:

  • power supply - swapped it out, nothing changed
  • monitor - tried on an LCD at 60 Hz and a CRT at 85 Hz - does it on both
  • hard drive - turned it off, same problem
  • sound card - took it out, same problem
  • CPU and case fans - unplugged them, same problem
  • electric grid / environmental factors - tried it in two different houses in two different cities

The only thing I've done so far that's made any kind of difference is underclocking the CPU, a Pentium III 1400S. (Actually, I had to drop the FSB and memory clock to do it, so I underclocked a number of things). This didn't get rid of the lines, though - it only changed the pattern.

This last bit leads me to the conclusion that the lines are caused by radio frequency interference generated by the CPU. However, if that's the case, why does it happen with some cards and not others? So far, this problem affects the GeForce2 Ultra and the G400 MAX, but not the 3D Prophet 4500 or the Rage Fury MAXX. Actually, it's even stranger than that: the G400's secondary VGA output seems to be unaffected. (This wasn't the case with the GF2, though.)

Gahhh, I'm getting stumped here... aside from wrapping my whole setup in tinfoil, I don't know what else to try. I'm almost tempted to buy another G400 to see if it has the same problem. What happened to that legendary Matrox image quality?

Truly, this problem is utterly bizarre.

Last edited by maximus on 2014-03-12, 05:43. Edited 1 time in total.

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Reply 1 of 13, by Shagittarius

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I don't have anything to add since the last thread but I just wanted to comment that this is an interesting but frustrating problem. I like your tinfoil idea =)

Maybe try it with either PSU outside the case where you can move it around and watch the patterns?

Reply 3 of 13, by maximus

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Mau1wurf1977 wrote:

Looks like you haven't swapped the motherboard.

Could be bad caps. Got any other boards to try the cards?

This will be my very next stop. Currently building a suitable AGP system. I'll update with results when I have them.

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Reply 4 of 13, by maximus

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Update: just tested a new-to-me TNT2 Ultra. No wavy lines. That doesn't rule out the motherboard as the problem, but it would have to be very selective about which cards it affects. So weird.

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Reply 6 of 13, by maximus

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Mau1wurf1977 wrote:

Currently working on a Voodoo 2 Super Scoket 7 scaling review and I noticed that with the faster clocked K6 chips I get vertical patterns.

Hmm, that's interesting. What are you using for a 2D card? Does it get lines on its own, or only when hooked up to the Voodoo(s)?

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Reply 7 of 13, by jwt27

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What happens if you enable/disable spread-spectrum modulation in the BIOS?

Reply 8 of 13, by sliderider

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maximus wrote:

Update: just tested a new-to-me TNT2 Ultra. No wavy lines. That doesn't rule out the motherboard as the problem, but it would have to be very selective about which cards it affects. So weird.

Have you tried the wavy line cards in other motherboards to eliminate them as the suspects?

Reply 9 of 13, by maximus

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jwt27 wrote:

What happens if you enable/disable spread-spectrum modulation in the BIOS?

The TUSL2-C doesn't have a spread spectrum option, unfortunately.

sliderider wrote:

Have you tried the wavy line cards in other motherboards to eliminate them as the suspects?

I'll be doing that as soon as I get my new build up and running.

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Reply 10 of 13, by Tr3vor42532

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Does it happen in all resolutions/refresh rates? I wonder if that's a factor.

Its probably just RFI from your computer interfering with something on the card.

My YouTube channel: https://www.youtube.com/user/Tr3vor42532

Reply 11 of 13, by Mau1wurf1977

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maximus wrote:
Mau1wurf1977 wrote:

Currently working on a Voodoo 2 Super Scoket 7 scaling review and I noticed that with the faster clocked K6 chips I get vertical patterns.

Hmm, that's interesting. What are you using for a 2D card? Does it get lines on its own, or only when hooked up to the Voodoo(s)?

Matrox Millennium. I get the lines only when playing games. They aren't really lines, more shadow like vertical bars. Quite faint and nothing too bad but still visible.

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Reply 12 of 13, by maximus

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Update for posterity:

I did some more testing, and I think I've finally gotten to the bottom of this.

I tested both cards in a different machine, and they still have the problem. That rules out the motherboard as the culprit.

I also went ahead and bought duplicate cards, so I now have 2x GeForce2 Ultra and 2x Matrox G400 MAX (dumb, I know, but what the hell, they were cheap). All four cards have the problem, so I can rule out the possibility of the cards themselves being damaged.

The good news is that I found a way to mitigate the problem, if not solve it outright. It turns out that Powerstrip allows you to make very fine grain adjustments to the refresh rate. This dramatically reduced the wavy lines on both the Geforce and the Matrox.

Fun bit of troubleshooting, all in all 🤣

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Reply 13 of 13, by obobskivich

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Very bizzare - glad you found at least a partial solution. The only things I was going to ask about was changing AGP/PCI freq or adding shielding to the card (you can buy shielding material on Amazon - it isn't "cheap" but you don't need a lot so it wouldn't cost a lot).

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