KVM Interference

[ensane]

This is not a fully linux related issue, but I figured I could see what people could suggest around here anyway.

I have a KVM, I have been using it for about a year. It has always worked nicely, then the other day I decided to install windows on a second machine. THe video was all messed up, the screen would shift in wierd places. It would occur when there was video activity mainly, but it would also happen in idle. Well I thought it was a video card on the windows box only type of problem, but then I noticed these faint wavey lines traveling downward across the entire screen when switched to my linux box. Just a moment ago I was able to stablize the lines, by disconnecting it, and unplugging all things that could cause interference. But its still doing it, it started up again a second ago. I just bought a new KVM, thinking the old one went bad, I plugged it in, and the wavey lines were there instantley.

I am using a IOGEAR KVM, and all my hardware, including ethernet is connected to a power surge protector. I have a router as well. THere is an old boiler heater vent about 3 to 5 feet away from my linux machine and the cables. Other than that i can not figure out what could be causing this. Any ideas?

Oh yeah I want to also mention that when I am not running xserver, or switch to a tty terminal by using ctrl-alt-f5 (for instance) and its just a black plain text screen there is no wavey lines.. though I got the distortion on the windows box with as little as 8 colors. If i were to unplug the kvm and use the monitor directly.. the distortion goes away and never returns for both the machines.

[timothykaine]

You could try changing up your refresh rates, but it sounds like outside interference. Head down to your local PC odds-and-ends store and find yourself some shielded KVM cables or shielding sleeves. And of course try to keep it a safe distance from heaters, motors (yeah, even your PSU), and the actual monitor itself. If you have a desk you can tuck it under, do so.

[canon006]

I'm not sure if it's exactly the same thing I have going on, but it sounds similar. I have a Belkin KVM and a Samsung monitor, I got a new video card for my Windows box and started noticing similar odd interference, and it seemed to carry over to the linux box. What seems to have fixed it was lowering the refresh rate on the Windows side, from 75hz to 70hz (these are both at 1280x1024).

I'm pretty sure it's either the age of my KVM (almost 3 years now) or the new video card which needs an adapter to convert from DVI to VGA, since it's dual-DVI. Are you using that sort of adapter on any of your video cards?

BTW, my video cards are an Asus GeForce FX 5200 and an XFX GeForce FX 6600GT, which replaced an ATI Radeon 9600XT. Match any of your specs?

[ensane]

Monitor: Samsung 753DF
Linux: Nvidia TI 4600
Windows: Rage 128 Pro

The problem starting happening the second I put that Rage 128 Pro on. Its a special video card and requires its own cdrom driver, none of the ATI website drivers will work for it. I almost think that this video card was used, and taken out of a Gateway system. The thing is though I've connected the kvm to JUST the linux box and get the same wavey lines. Right now I've messed around with resolutions and what not, and did a reboot on my linux and for the current moment the lines are gone. But it seems everytime I make them disappear, they eventually reappear after the more windows I open or if i do a lot of activity on the other end of the kvm.

I am a little frustrated, I think i am going with the cable shielding, maybe this will help...

WHen i first rebooted the lines were gone, if I stare enough I can notice them starting to happen again, and soon they will be so noticeable my eyes will hurt. I have Windows Server 2003 running on the other side now, and its perfect, and I just let Windows choose the video driver.. I can not figure this one out.. nothing makes sense...

[techwise]

It is possible, that just by coincidence your kvm has gone bad. Borrow one from somewhere and see what happens,

Mike

[canon006]

I'm not sure it's the KVM, my set up works fine until I turn on the Windows box, and then clears up when I lower the refresh rate on it. I think it might be that new video card or the adapter for it, it's the only thing that's changed and the problem only started after that. I'll have to see if I can borrow my roommate's KVM to test and maybe try some different ports on mine. So far it's been easy enough to work around and hasn't been annoying enough to get me really motivated to find a fix.

And my monitor is a Samsung 955DF.

[ensane]

yeah I am borrowing a friends of mine, I had bought a new one, its a Belkin, and the second Iput it on the system it started doing it, even though I only had connected the linux box only. Right now it looks stable from afar, but a closer deeper look at the edges shows a slight interference. I was wondering if a wall heater would do it. Its one of those base board heater apartments that has a boiler somewhere and it radiates heat. Also I use a wireless mouse. Anyone ever experience that interfering? My next step is to simply move everything from this room and see what happens in another room, away from whatever could be causing this. Another idea is that maybe a neighbor right next door has something that could be causing it. Or what about my cell phone? So many ideas.. this has got tobe the biggest thing I have ever troubleshooted.. LOL!! Oh well thanx for all your suggestions!

[gampy]

Hi ensane,

Have you tried using individual mice for each PC? Sharing the common monitor and keyboard shouldn't cause any problems. I'm using an I/O Gear KVM to switch between my Server (Linux) and my multi-booted primary PC. I have Linux, WinXP and Win2K installed on different partitions on my primary PC. None of the three OSes show any visual artifacts or defects while being controlled through the KVM switch.

The problem may very well be the wireless mouse. I use individual mice on these systems of mine. I have a PS/2 port KVM switch and I really don't want to use a USB/PS2 adapter. Unless you're using a really high end KVM, like those manufactured by Rose Electronics or Cisco, it's been my experience that usb mice can cause hiccups for inexpensive KVM switches.

As far as interference is concerned, I really don't suspect that the baseboard heater would cause you much grief. Are you by any chance using fluorescent lighting where you PC is located? Another attempt at troubleshooting would be to stretch the cables out (as straight as you can) so that they aren't "bunched" up at all. Make sure that you haven't got any extension cords 'running' over or close to the KVM cables.

[palinux]

I ran into a very similar problem about a year back when I replaced my old ball mouse with a optical mouse The screen went wavy and I quickly switched out the new optical mouse for a new ball mouse. Problem vanished. I believe I was using a Belkin KVM then, can't remember. I now use a LinXcel KVM, but can't say for sure which KVM I used with the optical mouse.

I'm now wondering if your wireless mouse might be creating some interference.

[ensane]

Well I had disconnected the mouse. Didn't affect it any. I think I MIGHT have found the solution. The KVM I use registers my mouse as a generic wheel mouse. But when I would hook the mouse directly to the computer it would register as a Miscrosoft Wheel mouse. Before I had the computer set my monitor as a specific Samsung Model that it is.. so I set my computer to a VESA model.. so far this seems to work, though like I said before the problem would come and go. So we will see. I am thinking this might work because I have a windows 2003 server install that used the generic driver that came with the OS and it does not bounce like the windows 2000 install I have as a dual boot on the same system that has the specific driver installed that came with the card.

Thanx everything, I'll keep you all updated.