Problem: It appears that when I turn on my second monitor my internet connection slows waaaay down.

Hardware: 20" iMac purchased just over a year ago, the week that the current models were introduced (it's the aluminum and black one) and a 3 year old 20" Dell flat panel monitor used as a secondary screen (I think it's the FP2001). Linksys wireless G broadband router (it's probably 2-3 years old). I have a Mini DVI to DVI adaptor/DVI cord connecting the computer to the monitor.

Details: I have been running this setup ever since I bought the computer and haven't experienced any problems until recently. When I turn the Dell monitor on my internet connection slows way down. When I turn it off it runs at normal broadband speeds. Can anyone explain this?

10/20/2008 5:12:09 AM

I can't imagine any sort of scenario where a monitor's use or disuse would have any effect on network speeds whatsoever. I'm not doubting you, but it's really weird.

Being I know about dick-all for Macs, I'll let someone else actually try to troubleshoot.

10/20/2008 9:37:34 AM

maybe it could be interference from all the devices being too close to each other?

10/20/2008 10:23:47 AM

10/20/2008 11:40:41 AM

Is it possible there's some kind of weird EMI coming from the monitor's power supply?
Also, this only happens when you enable the second monitor, or when you physically turn it on?

10/20/2008 1:00:17 PM

wired or wireless?

and what happens if you turn on the second monitor and use the other network interface?

10/20/2008 1:09:35 PM

IRQ conflict?

10/20/2008 2:02:49 PM

Odd as it is, I've experienced a similar issue with wireless only - you didn't mention how yours was connected.

I used to have my router sit between my two Samsung monitors, so that the antennas stuck up behind them. The wireless internet from it was always crappy at best until I moved it out from behind the monitors. I eventually mounted it on the wall above them, and since I did, it works just fine.

10/20/2008 4:30:05 PM

It only happens when the Dell monitor is turned on. It's always connected but it only affects the wireless signal when it's on.

And my internet is wireless. The router is in my roommates room which is approximately 40 feet from my room.

I have a WD external hard drive that sits between the computer and the monitor, which is always on. I don't know if this could be a factor as well. However, as far as I can tell it doesn't seem to have any affect.

10/20/2008 8:40:16 PM

heh if its the monitor then it needs better shielding...


badly

10/20/2008 8:54:10 PM

again, i would check for IRQ conflicts. i have no idea how to do this on a mac though.

the computer parts in this story will show my age...

my freshmen year at state i had to get a network card for my computer because it didn't have one. i picked one up from walmart and any time i'd pull up a web browser the monitor would go crazy. turns out the network card was using the same IRQ as my state-of-the-art TNT2 graphics card. resnet came out and fixed it by installing a new network card.

10/20/2008 9:09:00 PM

^ I thought you were joking about the IRQ thing.

I'm pretty sure, for one, that EFI did away with IRQs, and secondly, IRQ conflicts in general aren't a problem on modern hardware, and finally Macs have NEVER used IRQs that were user-settable.

This is going to be either a really odd hardware failure (like maybe a short in the ground on the video connector), or a really weird electromagnetic interference issue.

It could possibly be a software issue, but that seems unlikely to me. I'd boot off a linux live CD and see how linux handles it (assuming you get can linux to detect a second display).

10/20/2008 9:22:44 PM

I've been running this setup for a little over a year and haven't experienced any problems until recently. I have noticed that lately when I turn on the Dell monitor it makes a faint crackling type sound (crackling really isn't the right word but it's the closest thing I can think of). The sound I can most closely relate it to would be the sound pop rocks make after you put them in your mouth, but it's not as loud as pop rocks are. It's very faint. This sound lasts for about 5 seconds while the LCD monitor warms up. I think this sound started about the same time I began experiencing issues with my internet connection. I can only assume this would suggest that something is failing within the Dell monitor. Any thoughts?

10/20/2008 9:35:53 PM

^^ oh, i wasn't aware of the progress of IRQ. they weren't user settable on that computer either, which is why i had to get a new network card (different manufacturer) to get it to work.

in any case, sounds more like weird electromagnetic interference instead at this point. why don't you try temporarily running a network cable from the router and turning wireless off to see if it works better?

10/20/2008 9:53:05 PM

^^ i know what sound youre talking about

10/20/2008 11:21:41 PM

^^^

Ok, you're going to need to change some variables in order to troubleshoot this.

either try a different monitor
or run a long cable to the router

10/20/2008 11:47:07 PM

^^^^ i know that sound you describe

i happens with my dell branded 2208W

i am pretty sure that noise is completely related to the thermal loading in the plastic casing when the screen turns on and warms up

about 15 minutes or so after i turn off my monitor, it will make that noise and it cools down and shrinks

[Edited on October 21, 2008 at 12:04 AM. Reason : 

10/20/2008 11:47:54 PM

I'm going with weird EMI / crappy shielding, at least for now.

10/21/2008 1:53:41 AM

I connected an LCD TV to the computer and the internet works just fine.

After I get home from work I'll try running an ethernet cable from the router to my computer.

10/21/2008 6:07:15 AM