if you are running ML then your 2.66 quad is the 4,1 Early 2009.
But you never mentioned what gpu you have and replacing - GT120?
The 7950 Mac Edition? fine, just follow directions to connect the power cables.
March 22nd, 2013 -- PART DEUX: Sapphire Radeon HD 7950 versus other Mac Pro GPUs (running StarCraft, Diablo, Team Fortress, FCPX, Premiere Pro, Photoshop, and LuxMark)
March 19th, 2013 -- REVIEW: Sapphire Radeon HD 7950 versus other Mac Pro GPUs (running DaVinci Resolve, Motion, OceanWave, Heaven 4, Valley, Civilization, and Dirt)
What you should be doing is run Apple Hardware Test off the OEM DVD, and I would have done a fresh clean install of 10.8.x on its own drive, leave what your working system was 'as is' to insure you don't carry forward 4+ yrs of old extensions and stuff that can cause mischief. They do, it does happen.
You think your issues now are with the logicboard? and that is why your graphic card is trouble? Or your card now is only issue? and failing. Made sure the GPU slot is clean and firmly pushed in; same for anything else you removed, and that in cleaning out dust didn't just move some to a new location.
Sounds like the cleaning and reassembly not the logicboard (and not sure GPU).
My current GPU is ATI Radeon HD 4870 512MB.
As you can appreciate, due to me not seeing and information on my monitors I can't run Apple hardware test, although I'd love to, as this would give me a clue as to what was going wrong and where.
I did carry out a fresh install of 10.8 recently onto a SSD (from App Store). Mind you if I get things going again I might carry out a fresh install of 10.8.
It's funny that you mention the GPU slot, because I've always had issues with having to re-sit the card when apple sent me a replacement two years ago. I also noticed during my problems recently, re-sitting the GPU seemed to provide different results when booting.
So perhaps the connection strip on the GPU is the problem. I hope it's not the slot on the Logic board.
How easy is it to connect to a different slot?
Check photos online
Did you look for photos of 4870
Sometimes the little "lock" which is hard to reach or breaks off (optional).
Making sure just like with DiMMs that it is FULLY seated in the slot, give it pressure.
I read the 4870's age and lack of all the specs and features ML can look for to use, plus that most found the 5770 bench and performs better - compare the two on www.barefeats.com rather than go by subjective tests and 90% of apps will do better (unless they have not been updated, or are optimized maybe for Nvidia architecture).
I can't run an Apple Hardware Test because I have no display.
I have no warranty.
The new Mac Pro's are unavailable to buy in the UK.
I ordered a ne w GPU (Sapphire 7950) to upgrade before my Mac Pro became unusable.
I don't want to blow my new GPU, but I have no choice but to plug it in so I can see what's going on.
The only alternative would be to purchase a second hand Mac Pro or to purchase a new logic board.
So is there a possibility that a problematic logic board could damage my new GPU?
No sign and unlikely.
I keep spares of even video cards around.
I would never use computers w/o a UPS. Lightning and storms and wind do interfere with our power.
As this thread started, it was opening it up and trying to remove dust and putting it back together.
One thread just closed that kept sounding to me like "this is a heat issue" turned out the fans on the front were not turning. A lot of things were tried to get to simple "clean those fans, use SCF 2.4 fan control to boost the fans.
Popele have baked their Nvidia 8800GTs to get them back working. And worked.
I would say you are over reacting but your own effort to clean dust was the only critical issue so far.
People change out video cards all the time, even as part of troubleshooting.
There are places that do that sort of thing and only charge if parts are needed.
Just thought I'd update this thread.
My GPU arrived a day early, so I put the guts back into my Mac Pro, being extremely careful. Booted her up in safe mode with one monitor and a keyboard connected and it worked.
This obviously isn't a thorough test. So next I'll carry out a Hardware Test.
Howevr - what is the best procedure/order for plugging all the peripherals back in? Remove power cord and plug one device in, power up, shut down and continue plugging devices in like this. Or remove power and plug all devices in and boot in safe mode etc.
It's Thursday and everything is fine, although trying an Apple Hardware Test was unsuccessful. Keeping the D key pressed straight after the bong didn't seem to do anything. Really impressed with the Sapphire 7950 though. Definitely noticed a performance boost. Also just ordered a replacement PRam battery, concidering my current battery is four years old.
If everything stays the way it is, I can only comment that giving the old girl a spring clean moved some dust around the GPU causing it to overheat etc.
Never mind. I was planning on upgrading the GPU anyway, it just turned out sooner than later.