The 5770 and 5870 support up to three simultaneous displays each. You do not need an additional graphics card, although that is one possible, but very expensive, solution.
The 5770 and 5870 have a shortage of power to run converters to what ATI calls "Legacy" connection methods. In order to connect three displays, all converters must be ACTIVE POWERED adapters.
DVI for a display wider than 1920 wide requires a Dual-Link cable (or the cable attached to the display with no adapter). Dual-Link does not mean two displays -- it means that the cable has two sets of data lines to carry the large amount of data needed by such a wide display.
This page from AMD/ATI web site lists many Adapters/Converters ATI/AMD approves for use with its display cards. Read very carefully. ACTIVE POWERED Adapters/Converters for Mini DisplayPort are listed in one section.
Apple's recommended "Mini DisplayPort to Dual-Link DVI adapter with USB cord for additional power" costs US$100. Other approved solutions are available from Amazon at prices cheaper than Apple's. Amazon's search is an approximate search, and will give you chaff as well as the good stuff. Read carefully -- it must say ACTIVE and MINI DisplayPort.
LordZedd, you are correct that HDMI and DVI Video signals can be produced from each other using a simple adapter that simply cross connects wires, and therefore does not need any power.
To get from Mini DisplayPort to Single-Link DVI to run a Monitor, an ACTIVE POWERED Converter must be used if you wish to have three displays on that card.
If you prefer HDMI (without sound) you can add a simple adapter to the DVI output to cross-connect the wires to produce HDMI Video from the DVI Video.
This explains the dilemma:
Connectivity Requirements: AMD Eyefinity technology is supported by graphics cards in the ATI Radeon™ HD 5400 series and higher. These cards can support up to six monitors (depending on the model), subject to the following restrictions:
• A maximum of 2 legacy monitors (VGA, DVI or HDMI) can be enabled simultaneously, provided that each monitor is connected either directly or via a “passive” DisplayPort™ adapter/dongle. “Passive” adapters/dongles will NOT support more than 2 legacy monitors.
• To enable support for more than 2 monitors, “active” DisplayPort™ adapters/dongles are required (or monitors with direct DisplayPort™ connectivity must be used).
• Approved “active” adapters have no general connectivity restrictions with AMD Eyefinity technology.
1st display: Connect the Wide DVI display to the DVI port using its own cable, or use a Dual Link cable. Plugs right in and works.
2nd display: use an ACTIVE POWERED adapter from the provided Mini DisplayPort to DVI. Connect the display with a DVI to HDMI cable.
3rd display: use an ACTIVE POWERED adapter from the provided Mini DisplayPort to DVI. Connect the display with a DVI to HDMI cable.
Thanks Grant, LordZedd.
Could you please clarify (and please excuse my lack of knowledge) - when you refer to the ACTIVE Powered do you mean that the adapter needs and extra USB cable to provide extra power - or does it include Active Single Link Adapter like for instance this one: http://accellcables.com/products/DisplayPort/DP/mdp_dvi_sl_active.htm ?
I already bought an extra, second hand graphics card Nvidia GeForce GT 120 and the third monitor works now, but what I've realised is that the performance on both cards has now degraded - some animations on the websites are now jerky and even creating new system folders and typing the name - it shows letters with the slight delay. Also - there is a buzzing in the speakers every few seconds - I'm wondering whether there is some problem with the power now that two cards are running simultanously?
I've read some reviews that using two apple adapters with Radeon 5770 was causing some problems as well - apparently they are pretty noisy etc.
Any suggestions or clarification on the above would be appreciated.
The requirement is that it picks up power from somewhere. There IS a lead on the Mini DisplayPort interface that can be used, and that is what the Accell ACTIVE adapters do. Those adapters are for sale in the US on Amazon.
The Apple adapter goes completely to the extreme and instead uses a different source (a nearby USB port) to pick up the power. This may make is a bit more reliable.
An adapter that is ACTIVE will have be sure to use that word in its description, to justify its higher cost to buyers.
Thanks for all the helpful info Grant! I'm in the same situation, now before I click 'purchase.' You're saying that an adapter such as this
http://www.amazon.com/Accell-B087B-006B-DisplayPort-Single-Link-Certified/dp/B00 4071ZXA/ref=sr_1_2?s=electronics&ie=UTF8&qid=1358451181&sr=1-2&keywords=DVI+HDMI +ACTIVE+POWERED+adapter+MINI+DISPLAYPORT
that says ACTIVE but NOT powered in the title-will work for this? All the non-usb powered adapters are a third of the price, just want to make sure I'm buying the piece that will work.
almost. That link shows me a (full-sized) DisplayPort version.
I think you want this one:
I am trying to beat casual readers over the head with the ACTIVE = Powered concept. The Ads will prominently say "ACTIVE" if they are, and not otherwise.
The Apple solution is truly an Industrial-strength solution. It is a full Dual Link DVI connector (with double conductors on three extra pairs of data lines). It also uses an external USB to pick up lots of additional power, from a source other than the graphics card.
... and it is Genuine Apple, and priced accordingly.
These AMD-specified ACTIVE Single-Link DVI adapter/converters (like those Accell ones) are about US$30 because they have driver electronics in them.
Simpler, cheaper adapters just have two connectors and some cross-wiring, no circuitry. But when you need to drive three displays, the graphics card runs low on power, the signal levels get too low, and your displays drop out. That's why you need ACTIVE.