3 monitors on a mac pro 4.1

Question

Hello
In trying to run 3 monitors on a mac pro 4.1, I have recently bought a Radeon 5870 card from Apple as advised by a 'genius' at the local apple store.
This setup does not work, even giving worse performance than the 4770 with 2 of the monitors (NEC 30" & Apple cinema 23").
Both these cards require 2 power connectors so adding another doesn't seem possible, however the 5770 uses only 1, so is it possible to run two 5770 and bring my spare Apple 23" in to use for a 3 monitor desktop? I have tried lots of permutations with both mountain lion and snow leopard, zapped pram, reset etc to no avail.
Any advice welcome!
Thanks
John Law
Bath UK

Answer 1

you probably didn't need 5870 as the 5770 also can drive 3 monitors but it is the screen resolution and adapters that make all the difference.
I assume as there was no Apple 4770 that you meant the 4870 that was a BTO at one point.
Apple Mini DisplayPort adapters: Frequently asked questions (FAQ)
http://support.apple.com/kb/HT3382
Guide to Apple graphic display adapters needed 
https://support.apple.com/kb/HT3235
Atlona (Dual Link) DVI to Mini DisplayPort Converter for Apple 27-inch LED and 27-inch iMac
http://www.atlona.com/Atlona-Dual-Link-DVI-to-Mini-DisplayPort-Converter-USB-Pow ered.html
Mac Pro (Early 2009), Mac Pro (Mid 2010), Mac Pro (Mid 2012): Issues with three displays and multiple DVI, HDMI connections
It's not the USB data that is needed to run three displays. It's the extra POWER. If you read the Apple article, they say the only solution they endorse is their US$100 Dual-Link adapters. Check the table at the end of the article.
Mac Pro (Early 2009), Mac Pro (Mid 2010): Supported display configurations
Readers here have found that if you have two Brand-X Powered adapters, aka active adapters, it also works fine. These do not always require another USB. If designed recently, they can pick up a power pin in the Mini DisplayPort interface.
AMD (makers of the 5770 and 5870) lists the qualified POWERED adapters that meet their most stringent requirements. Look down the page and you will find several qualified Active Mini DisplyPort to various others, such as HDMI. These adapters are available from other outlets, such as Amazon, sometimes for far less than the Apple adapters.
http://support.amd.com/us/eyefinity/Pages/eyefinity-dongles.aspx
The other desktop monitor will plug directly into the DVI port on the card and the 40 inch tv will still connect via HDMI over the second Mini Display port.
That will work only if you use an active Mini DisplayPort to HDMI adapter.
The only (someone) have found to work (2009)
http://www.alibaba.com/product-gs/337561577/miniactive_display_port_tohdmi.html
but you should confirm that they are really active before buying 500 of them.
You can connect a DVI to HDMI adapter or cable to an active Mini DisplayPort to DVI adapter but that won't give you any audio over HDMI. You could connect the DVI displays to the Mini DisplayPorts with active adapters and use a DVI to HDMI cable or adapter from the DVI port to the TV.
If you want audio via HDMI, you can use audio from the Mac Pro's optical output with this DVI to HDMI converter:
http://www.apogeeinc.net/products/item.aspx?item=2745