My main desktop is an Apple Mac Pro with an ATI X1900 Video Card
I’ve been noticing some strange video artifacts on my primary display for the last couple of months. They consisted of what appeared to be 1 to 2 pixel wide line artifacts across the windows of various applications. Sometimes they run for the full window width and other times they would not.
I noted these “lines” in a number of applications including, Safari, NetNewsWire, Mail, Photoshop Lightroom and even the screensaver.
These line artifacts began appearing about the time I upgraded OS X from Tiger to Leopard, so of course my first thought was that it was some kind of problem with Leopard. I never experienced this with OS X 10.4 Tiger.
With research I’ve found a number of people reporting similar line artifact problems with the X1900 Video card. Many of these problems were occurring under OS X Tiger and it appears that the ATI X1900 card is very sensitive to heat.
Some are guessing that Leopard places a higher load on the graphics processor which may be causing some of these issues to be seen in Leopard.
I’ve taken a couple of steps that seems to have mostly eliminated this problem for me.
1) I opened up my Mac Pro and used a can of compressed air to blow out all the dust that has accumulated in, on and around all the internal cards and devices. It wasn’t as dusty as I feared but every little bit helps.
2) I install a software utility call smcFanControl which allows the manual control of the base speed of all internal cooling fans. I used this to set the minimum base speeds up from 500 rpm to around 900 rpm. This provides additional cooling and air flow with little or no additional noise.
I’m not completely satisfied with this as a final countermeasure but until I find a better solution I’ll keep the X1900 as clean and cool as possible.
There is an Apple Support Discussion thread on this same issue.