Problem using 2 Graphics Cards in Mac Pro 2012

Thank you Illaass, but I had already tried those things. I hit post by accident and hadn't finished the whole discussion. Here's some additional information:

1. I originally installed the 8800GT in slot 3 and had the described problem. I then moved it to slot 2 and that made no difference.

2. Slot 1 has the 5770 and, now, slots 3 & 4 have USB3 and eSATA expansion ports.

3. PRAM resets, both with the additional monitors connected, and without them, made no difference.

4. SMC reset made no difference.

From everything I've read, including the system's instructions, it should accommodate 2 graphics cards. Is it possible that they have to be 2 identical cards?

Thanks again for your help.

Dan

Hi Illaass:

Thank you. This gets stranger. I tried connecting only 1 monitor to the 8800GT and that works perfectly as long as that monitor is plugged into connector 1 of the 8800GT. Plug that monitor into connector 2, or plug in 2 monitors to the 8800GT and it won't work after restarting. But, with only 1 monitor connected to connector 1, I've tried several restarts and it seems fine. I may try getting a newer card (an additional 5770), but in the meantime, I have a Displaylink adapter and will try to connect the 3rd monitor using that - the third monitor only has text on it. Thanks again for your suggestions.

Best,,,
Dan

Hi John:

Thank you for your insight. I think you may be right. I had read that the 2nd card might not display until the system had finished booting, but mine didn't work even then when I had 2 monitors connected to it. But, with only 1 monitor connected - and then it must be in connector 1 - it works fine. So, temporarily, I'm using the original 5770 for my 30" Cinema Display; 1 other monitor connected to the old 8800GT and the 3rd to a DisplayLink USB adapter.

Ultimately, I have to get another 5770, but they're hard to find except used and then you never know what you're going to be getting. For what I do, I don't need the latest and greatest video card - I do no 3D or gaming, but I do a lot of high-res photo editing and now some video editing. That's the reason I don't want to share the resources of the existing 5770 among more than just the 30" display. The other displays just have email, calendar, etc., so no big deal. So, in reality, the setup as I have it now is OK. But, it'll be cleaner if I find a good Apple-compatible 5770. Thanks again,

Dan

Thanks Illaass:

My problem is that the 5770 takes 2 spaces. I have 2 PCIe cards that provide USB3 and SATA ports, and I'd have to remove 1 of those cards to add a 2nd 5770. Since 2 of my monitors are only used for things like email, I don't need a powerful card for those 2 monitors. Perhaps I can find one that's a single slot high, like the old 8800GT, but that's also compatible with the MP 5,1. It doesn't matter if it doesn't come on until the system has booted since I've got the 5770 that does that.

Like you mentioned, there are much more powerful cards than the 5770 and perhaps 1 of them would drive all 3 monitors and be an even better solution than 2 5770s and still allow me to have the extra slots for my other cards. The problem is that they're expensive.

Thanks Grant:

I had 3 monitors, using the correct adapters, connected to the 5770 and got the impression that the card was dividing its resources among the 3 monitors and that was negatively impacting the performance of my main monitor - the 30" Cinema Display - where I do my photo and video work. My assumption was that its performance would improve if the card only had to drive that 1 monitor. I haven't done enough experimentation to determine if this is a true assumption, but I think I'm seeing an improvement, but that could be my imagination. What I need to do is time a few actions with 3 monitors connected, and with only 1, to be sure. Do you know of anyone who has done this kind of test?

Thanks again,

Dan

Hi Illaass:

Thank you, again. I just want to be sure I understand what will happen if I plug a PC card into my MP 5,1. My understanding is that the only drawback is that the monitors connected to it will not come on until after the system has booted, and that after that it will work normally. Is that correct?

Thanks, again

Dan