Here is my tinkering:
I routed power from the optical drive (second one) and just left the case open (no point in cable routing if i dont know the configuration will work to my liking, plus with the new 09 model seems as though the cable routing job will be impossible as shown in matthew.russo's configuration. I have provided the proper power to both of my cards without the use of my external power supply.
Cards: Factory Radeon HD 4870 512mb Ram. (Slot 1)
Sapphire Radeon HD 4870 X2 2GB Ram (Slot 2)
There is a trick to achieving this however. You cannot route the power strictly from the optical drive, you must take a 6pin from the original Apple Radeon card, and hook it into your second graphic cards 6 pin port, and leave the other one in its original state (in the orig apple card) then route the optical drive from molex to 1 6pin and 1 8pin converter (for my X2, other cards will just need 2 6 pins) and hok the 6 pin to the apple card and the 8 pin to the second video card. the cableling will have to be exact, if not the second graphics card will yield a red light and will not be supplied the proper power. (I did this configuration in the past without switching up the original 6 pins that came with the mac pro and found that my computer would shut down abruptly after 5-10 minutes of intensive use)
Another thing to note is, using a splitter to transforms into to 6+2 pins, will NOT work. Playing F.E.A.R 2 max settings, after about 20 minutes, the computer would shut itself off. I found running catalyst my Radeon 4870 X2 reached temperatures up to 70 degrees C. The only way to remedy this is the splice the connectors as I did with the optical drive route or to run the fan at 100% power (through the manual fan control in the Catalyst Control Center [CCC])
So far with the power to both of my cards. I was not able to recieve a video signal at all no matter what port I plugged my monitor into. I have since dumped the rom of my X2 and reflashed it using my own frakenrom that i made using pipomolo42's fixrom.py script method, and the first time it didnt work, i think because it errored but i didnt really pay much mind to it, went back through the forums saw someone else had the same error so i tried it again and sucess!... well kinda...
Both cards ended up working simotaneously, however, with the cooked rom I made (because the x2 is two GPU's) it seems it only flashed part of the card, only the master ? or maybe the slave? GPU was flashed, 1GB ram seen, + the 1st gpu in mac os x, in windows, it was a whole nother story, I couldnt even get the card to work properly. so I tried to reflash it back to the original bios, but alas now I have nothing but a black screen yet again.... I can't even boot off into windows or dos in it anymore. sigh, I guess I got greedy per say.... back to the drawing board. I am thinking about ordering another 1Gig rdeon HD 4870 and using it with the original mac, then just switching them both out or one of them for the X2 on super intensive games, at least until someone can get the card flashed properly.
Pics below of the connectors settings... sorry for poor quality, I don't have a digi camera!
the macbook pro's isight will have to suffice for now.
Yes I can close the case by pushing the cables into the square hole they are coming out of and letting the wires push up against the hard drive bays.
