Need help diagnosing 2008 Mac Pro - Vid Card or Power Supply?

[XianPalin]

Short story since I tend to write a lot: 2008 Mac Pro will turn on for half a second with GTX 285 hooked up, and then turn off. I put in an old 8800GT and it boots fine. Is this most likely a problem with the GTX285 (my guess) or could it possibly be the power supply?

I have a 2008 Mac Pro (8 core) with the following:
GTX 285, EVGA Brand (the way overpriced retail official Mac version)
2x optical drives
8x 1gb sticks
1x SSD, 3X hard drives

I dual boot into Windows to play games - not the best gaming rig but it works well. The other night I left it booted into Windows, and in the morning the machine was frozen. I turned it off, and then back on - the power in the room would flicker, the mac pro would turn on for half a second and then turn back off.

Long story short, it finally booted when I unplugged the two power cables to the 285. If I plug only one cable in to the port furthest from the back of the mac, the computer doesn't turn on still. If I plug only one cable into the port closes to the back of the mac, the mac turns on but doesn't boot. I have switched power cables, and the cable doesn't seem to matter, and I tried both cables with the 8800GT (it only requires one) and the mac booted fine.

I am guessing the video card is most likely to blame, but I also wondered if it's possible that the power supply is going bad and can no longer output enough power? I disconnected all drives except for the SSD since they're the only other thing probably drawing a lot of power right on boot, and even with just the SSD plugged up the problem persists.

Can I put the Mac GTX 285 into a PC and try to boot it to see if that is the problem? Will a PC boot with it hooked up?

And a follow up question assuming the video card is indeed the problem:
What is the best card to get for a 2008 Mac Pro that I can power off of those two cables?

Thanks so much for any advice.

 

[MacVidCards]

285 is dead, giving direct short, throw it out before you blow something up

 

[DanielCoffey]

And as for the "best" card, have a look at the sticky thread at the top of this sub-forum to check your options. You don't have to stick with Apple cards (such as the Apple 5770/5870) but you will have constraints according to which version of OSX you currently use.

 

[XianPalin]

I've been trying to read, unfortunately all the graphics stuff is a bit confusing if you haven't been following it at all.

What is the best Nvidia pc card that I can pop into my Mac Pro and have it work out of the box, without having an external power supply or needing to flash the card?

I am not worried about gaming under OS X or having a boot screen. I'm running Mountain Lion if that matters.

Can I pop in a 560 Ti and it will work fine?

 

[GermanyChris]

I've been trying to read, unfortunately all the graphics stuff is a bit confusing if you haven't been following it at all.

What is the best Nvidia pc card that I can pop into my Mac Pro and have it work out of the box, without having an external power supply or needing to flash the card?

I am not worried about gaming under OS X or having a boot screen. I'm running Mountain Lion if that matters.

Can I pop in a 560 Ti and it will work fine?

From the sticky:

6) What GPU should I buy?

This is a great question, and depends on your budget and what you'll be using the card for.

If you care more about gaming and have an unlimited budget, get a GTX 680.
If you care more about compute (CUDA/OpenCL) and have an unlimited budget, get a GTX 570.
If you can only afford a mid-rage card, get a GTX 660 Ti or GTX 660.
If can only afford a low-end card, get a GTX 650.

In general, if you are buying a card now, I would recommend getting a Kepler card and using Mountain Lion. If you really care more about OpenCL or CUDA performance, then the GTX 570 is probably the best choice. Brand of card does not matter, though I personally stick with EVGA in general.

If you are stuck with a MacPro1,1 or MacPro2,1 then your options are slightly different, since the Kepler cards don't work in Lion.

If you have an unlimited budget, get a GTX 570.
Otherwise, get a GTX 560 or GTX 560 Ti.

I think it's unlikely that the Kepler cards will ever be supported on Lion, which does limit the options for older Mac Pro systems.