3,1 Mac Pro: Dual graphics cards, one Mac and one not?

[GFLPraxis]

Hello! My wife uses a 3,1 Mac Pro for her photography. The current setup:


* Quad 2.8 GHz Xeon CPUs
* 20 GB ECC RAM
* 256 GB SSD + two 2 TB drives in a RAID for archiving + fourth drive for Windows/Boot Camp
* Radeon X1900 XT
* Two 1080p monitors hooked up over DVI
* OS X El Capitan

The thing performs like a champ. Single core CPU performance is comparable to a modern Mac Mini, but multicore performance is comparable to a current iMac! Sure, the RAM is a lower speed, but volume tends to matter more. The SSD breathes new life in to it and I love this box.

However, I've started getting her in to some older gaming titles, most notably Starcraft 2. That old Radeon X1900 XT can only handle low settings.

We'd like to:
* Run Starcraft 2 and similar older titles on high settings
* Run three monitors, including an old Apple cinema display at 2560x1440.


But, genuine Mac cards for this are absurd! A genuine Mac Radeon HD 5770 costs over $200- this card runs around $80 for PCs, or less.

Flashed graphics cards and apparently newer NVidia cards run fine, apparently, on El Capitan, except that you lose the boot screen, correct?

My question is this:

If I keep the X1900 XT in the Mac Pro, and slap a newer card (say, a Geforce GTX 660 Ti) in there, and keep one monitor hooked to the X1900 XT and the rest to the new Geforce, will I get the best of both worlds? (i.e. a boot screen on the one monitor, and then all monitors functioning after boot?)

 

[Fl0r!an]

A properly flashed 5870 will give boot screens. Can be done at home, no black magic needed. Applies to some other PC cards, too, but the 5870 should already do what you need.

 

[Flint Ironstag]

It should work as you expect. I have a similar setup with a Mac GeForce 8800, and an unflashed Radeon 7970. Works like a charm. The 8800 runs a TV, and the 7970 drives the 2 primary monitors and handles gaming duty. 8800 provides boot screens.

 

[JoSch]

I added a 750Ti to an HD5770 Mac edition. The HD5770 gives me the boot screen like your X1900XT does.
The 750Ti should easily handle Starcraft 2.
Also an 750Ti doesn't need an additonal power cable, at least the standard not OC ones.
If you let X1900XT in your machine, you don't need to flash the 750Ti.
The only drawback is, that you need to update the Nvidia web driver before updating your system, because Apple's standard drivers crash with a 750Ti.