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)Guide to Apple graphic display adapters needed
Atlona (Dual Link) DVI to Mini DisplayPort Converter for Apple 27-inch LED and 27-inch iMac
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.
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.
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)
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:
If you follow the official recommendations of Apple, on very close reading, they say for three displays that require adapters:
1) Use only ACTIVE (powered) adapters.
2) The only ACTIVE (powered) adapter Apple sells is the US$100 Dual-Link DVI adapter.
3) if you want genuine Apple adapters, that is the one you must buy.
ATI/AMD, the maker of the card says they have tested and approved a whole raft of adapters, including some that are ACTIVE Mini DsiplayPort to Single-Link DVI (works for up to 1920 wide or 1080p) in this article:
In the US, several of these are available for less at Amazon.
Read Carefully!! It MUST say ACTIVE or it is not. It must be Mini DisplayPort or it will not fit.
Thanks for the info, I've now returned the 5870 and ordered a 5770 + an active mdport adaptor so possibly I'll be able to run 3 monitors when they arrive.
Prices for non apple adaptors from accell were $91.33 on US Amazon & £123 (thats $194.39) on the UK Amazon site! I bought the far cheaper apple adaptor...
From your logo I 'deduce' that you are a Sherlock Holmes fan. Have you read the new 'House of Silk' from Anthony Horowitz? If not, highly recommended!
In the US, for displays up to 1920 wide, this third-party AMD gold certified ACTIVE adapter is available at Amazon for under US$35;
Accell B087B-006B UltraAV Mini DisplayPort to DVI-D Single-Link Active Adapter ATI Certified (Black)
And for displays wider than 1920 wide, this third-party AMD gold certified ACTIVE adapter is available for under US$90:
StarTech adapters that will do this job are also available.
Thanks for the reading recommendation. I do like Sherlock Holmes.
I chose my Avatar from the very limited group that was originally available. I mainly wanted to suggest that I was good at analyzing problems.