having serious GPU compatibility issues with a macpro tower donated to our art collective

[falawfulz]

the tower is mac pro model 3.1 xenon 2.8GHz 2xquad core

we bought the ATI Radeon HD 5870(2xmdp 1dvi) "upgrade" card that is compatible for it but any os above 10.6.6 looses functionalities in the card

we also have a pair of NVIDIA GeForce 8800 GT(but no power for them and they stop working above 10.5 if i recal correctly) and a small pile of radeon 9600/9650 cards from a g5 build we where doing but they do not show up as being plugged in, in system profiler but do not show any output support and do not output. although they may of with 10.5?

 

for the last month or two i've been slowly working on updating/upgrading a donated apple tower for "visuals" purposes at music events and art events(we have up to 14 projectors available to us but have a minimum of 4 on hand always)

and it seems that every graphics card we have around here is not compatible with any os above 10.6.6(the older ones 10.5), another issue i am noting the farther i dwell into this build is that i can only use one of the 2 x16 pci slots and one of the 2 x4 ones at a time as the "expansion slot utility" does not work on this model, has anyone figured out a way to change that?

basicly i am hoping to find out more information on how to fix whatever the update did to the drivers that make the cards work with all outputs and best resolution options and would also love to figure out how to get newer better tech in the graphics slots so i can get the maximum bang out of this machine. so far google has only informed me of what the issue is and brought me to a couple of forums inclusing this lovely forum that may help me figure out how to fix the issues or if need be build a better machine for what we want to do.

 

Tried: distributor retail osx instal discs 10.5-10.8 (currently running a carbon copy of my macbook's 10.6.8{anything above 10.6 did not work with any card and it has the programs already installed(well 10.7/10.8 would work with the 5870) above 10.6.6 didn't work well with the over priced 5870 "upgrade" our apple tech bought to test and make sure it was a gpu issue and not a tower problem after he hooked us up with the shops "recycling" sadly apple does not do returns on "outdated technology" so i'm paying him off for the card purchase as that was not expected nor should it be his issue})

 

Results: the best card functionality is in 10.5 but we do not get syphon protocal which is important to what we do.(syphon is 10.6 and above)

 

just to clarify the two things i'm trying to figure out at this moment are can i bipass "expansion slot utility" so i can change the port settings on my pci slots or has someone built a program that will do the same thing?

and

how can i fix the update issue that made the cards part of the planned obscolescnce routine?

 

also i'd like to say thanks for all your hard work at freeing up what options we have for our builds. if i broke any posting rules or rambled a bit too much i appologize, it's been a long session of diving and digging through way to much information, trying to sort out the various issues i'm encountering and would like to try and be as clear as possible in whats going on for ease of finding cost effective sollutions.

thanks