Quote Originally Posted by samsc View Post
when a refresh rate says its 75hz its not - its 75.02, or 75.03 - and its slightly different at every single monitor resolution - and different between dvi and vga- ( even at the same resolution ) ( connecting one monitor with vga and the other with dvi - i have seen this not work well )
and these slight timing differences can cause problems.
its something that needs testing on end users system - as its not always something that is a problem.
One of the things I have been researching is DVI to 5-Wire BNC connectors. Since obviously we all have a more common tendency to drive our projectors with 5-Wire BNC I figured the would be one less connection in the path to troubleshoot.

What I found is something from Gefen which has a Male DVI which 'Y's out to 5 BNC plugs and a Female DVI plug. I didn't know why they did this. It didn't make sense to me. The explained it would allow a user to attach a DVI screen and run a 5-wire signal simultaneously.

Surprising what I found!
Apparently many video cards can drive DVI and VGA simultaneously through the same port. In this case, a user can attach one of these DVI BNC Y-adaptors and view an analog and digital signal simultaneously on two different output devices.

(Basically, I can setup my racks to output DVI and BNC simultaneously without needing a converter.)

I have been researching the video cards in MACs. They perform this function. I am reading into the Quartz specs to see how this is controlled and if it produces signal overhead. What I am thinking is that perhaps a command key can be entered by a user into the terminal which will disable either the DVI or the VGA.
(~"PLEASE NOTE THIS IS VERY DANGEROUS UNLESS YOU KNOW HOW TO HACK IN UNIX"~)

The hope in this discovery is to determine if some of the overhead issues can be alleviated by using this fix. I will report further as I find out.