The standard disclaimer - This is how I did it. It worked for me. If you explode your G5, Radeon X800 XT, or your house, car, boat, etc. I am not liable! I am providing information based on my own knowledge and experience. I believe that all steps necessary are included, but if something is missing, I'm sorry in advance. Anytime you work with electronics you should observe caution, and use anti static mats, wrist straps, etc. so as not to damage your sensitive electronic components.
Now, on to the introduction!
I'm pretty new to the Mac scene, but I've been given a pretty nice PowerMac G5 computer tower, and I have finally found the best video card (with an ADC port) to use with it and the Apple Cinema Display. Being a PC user, I had no idea what ADC was, but after some research, here's what I discovered - You don't need a power cord for your monitor! The power comes from the video card, along with a USB connection so you can plug USB sticks n' stuff into your monitor.
This creates a problem, though, because you can't use Apple's cinema display with a video card with standard DVI out only unless you buy the (still) pricey DVI to ADC converter, which runs around $100 used. Also, it has to be a 'Mac' version card - or a PC card that has been 'flashed', but I'm not going into that here because I'm only just starting to learn about that.
That being said, I went on the hunt for the best card to use in my older PowerPC Mac. Again, not being an Apple guy, I didn't know that this run of PowerMac's were the last to use the PowerPC CPU. After this version, Apple went with Intel, and PPC has been left in the shadows of time to fend for itself. You can't upgrade to OS X 10.6, and many plugins like Adobe have dropped PPC support. I like the underdog, though, so this machine is just for me! It's fast, quiet, and has the nicest case I have ever had the pleasure to own.
I finally located a working Radeon X800 XT card for my G5 after a long search and the acquisition of several non-working cards. Don't get me wrong, I don't think anyone was trying to rip me off, but these cards apparently run hot, and that seems to be the problem with the broken cards that I ended up with.
** Just be warned - these cards are pretty finicky, and you may get a good one or you may not! **
After getting a working video card, I began the search for a cooler that would work with the Radeon X800 XT, and I found a new Zalman VF900-Cu Heatsink on Amazon.com! (at the time of this instructable's writing, JURRASIC PHOTOS had 9 left) It included heat sinks for the Video RAM as well, which is a plus, since one of the cards that I ended up with had some fried letters on a VRAM chip on the bottom of the card.
I read all that I could find about this install, but most people just told me about what they did - no pictures. I like pictures, so I decided to make an instructable that had instructions AND pictures.. Hope it helps you old-tech lovers out!