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Discussion Starter · #1 ·
I have a Mac pro 3,1 with a Radeon 5770 card. I realize I can get it to run three monitors only with the use of two expensive Apple Mini DisplayPort to DVI adapters.

Has anyone installed two video cards in their Pro? I was considering throwing in a one-slot card to run the third. Would simply be interested in knowing whether anyone has succeeded.
 

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There are people who have powerful Nvidia PC (non-EFI) graphics cards, and also have a GT-120 card installed in order to get boot screens at startup. So I'd have to think you could install a GT-120 to run the third monitor. It doesn't require a power cable and they're generally pretty inexpensive.

The only question is whether mixing an ATI card with a Nvidia card is an issue. But I think they can coexist in a Mac Pro. Both are natively supported in OS X.

There is a problem though if/when you use Bootcamp. Windows 10 doesn't play nice with two video cards, and people have found that they need to remove the GT-120 when booting into Windows.
 

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Discussion Starter · #3 ·
GT-120 was what I was thinking.It would be nice if a card that has three ports could run thee monitors out of the box!

No issues here with Bootcamp. This computer has never touched Windows!


There are people who have powerful Nvidia PC (non-EFI) graphics cards, and also have a GT-120 card installed in order to get boot screens at startup. So I'd have to think you could install a GT-120 to run the third monitor. It doesn't require a power cable and they're generally pretty inexpensive.

The only question is whether mixing an ATI card with a Nvidia card is an issue. But I think they can coexist in a Mac Pro. Both are natively supported in OS X.

There is a problem though if/when you use Bootcamp. Windows 10 doesn't play nice with two video cards, and people have found that they need to remove the GT-120 when booting into Windows.
 

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Discussion Starter · #4 ·
I installed a Mac version of a Radeon 4870 with a Radeon 5770 in the same 3,1 box. Works fine for testing on three monitors, but I realize that the 4870 really needs TWO power cables to function fully (some artifiacts at boot-up confirm that). The 5770 requires only one.

Going to use a Molex-to-six-pin cable that came with another card, and hook to the spare drive bay connector, but I'm not sure whether it supplies as much power as the regular power connectors on the motherboard. Will report back.
 

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Discussion Starter · #5 ·
Tried to use an AMD PC version of the Radeon 5770 as the second card--only one power cable needed. However, the only Radeon 5770 that does not work with my Mac Pro is the XFX version. Seller was kind enough to take it back. Used a PCI-e-to Molex from the second optical bay. Not too hard to thread it through the cable opening. However, the cord is about 3 inches away from reaching the card. Now waiting for a longer 6-pin to be delivered--nobody in the city seems to have one in stock.
 

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Macfury, there's some good info here, starting with post #38. There's also a link to voltages supplied through the molex connectors in post #40.
 

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Discussion Starter · #7 ·
Thanks gwillikers. Based on that information, I took the plunge and connected the one power lead to the motherboard and the second one from the optical drive to the new card, a PC AMD Radeon 5850. I had to wire it over the edge of the optical bay with the panel removed while waiting for my 6-pin extender. The Pro likes the 5850 and since I have a Mac-blessed Radeon 5770 installed, I get the boot screen. Better yet, the 5850 cost me only $40, while Mac 5770s are easily triple that price.

For anyone who cares, I took all of my 2GB 667 MHz RAM modules from the Mac Pro 1,1 and installed them in the 3,1 for a total of 16 GB--taking a hit of 4% processing speed. I then took all of the 1 GB 800 MHz modules and put them into the 1,1. They are fully forward and backward compatible although the 800s will operate at only 667 MHz in the 1,1.
 

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Glad it worked.
I have a 4 GB Nvidia GTX 680 that I paid an arm and a leg for. But it's been great for gaming so I guess that somewhat justifies the high price. :cool:
 

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Discussion Starter · #10 ·
Glad it worked.
I have a 4 GB Nvidia GTX 680 that I paid an arm and a leg for. But it's been great for gaming so I guess that somewhat justifies the high price. :cool:
The 5850 will play Doom--1995! The GTX 680 Ti was going for around $100 on the used market right now, but so many variations I didn't want to take a chance. I remember that you like to flash them, so not a problem for you!

I put the 4870 in my 1,1 and realized I needed a second 6-pin cable from the motherboard to the card. You'd think a city the size of Toronto would have at least one place where you could buy one retail! All special order at ridiculous prices. Why would I want to go to Canada Computers or NCIX so they could order something I could order myself and have delivered to my home?
 
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