Rule One: Mini DisplayPorts must have active adapters when you are using three displays. I use these:
Rule Two: Choppy video can be a disk speed problem, a cable/bus problem, a video format problem, or a video board problem.
What a monitor will/will not do is often a monitor problem. I have two 27" 1080p displays on mini DisplayPort and a 37" 1080p HDTV on the main DVI without issue.
hope this helps
EDIT: if the Dell monitor is greater than 1080p, it probably requires two ports. And if that's the source of the window you talk about, it's too big for the other monitor.
Thanks for your response.
Bear in mind - I am coming from the same twon montior scenario with the old card. Exactly the same resolution and setup and it was smooth. This is not. I wonder if there is a software upgrade that is required or something, Also every other part of the hardware setup is exactly the same. The only thing that has changed is the new card and worse performance which really surprised me.
That is truly depressing news about the active adapters. Not sure about this - I may just send the sodding card back to apple.
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.
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.
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:
Active MDP to HDMI audio and video converter:
Discussion: Using three ports.
Hello Hatter, thank you for your effort but that does not really solve my problem.
I am trying to connect the DVI output of the Radeon card to my Main monitor, and that works fine. I can also connect the mini display port to the old VGA monitor, and that also works fine. But I cannot also connect the mini display to HDMI TV (via the adpator I bought for it) all at the same time. I can have 2 out of the 3 but not all three.
But before I bother with this anymore I need a resolution as to why the grpahic performance is so terrible. If anyone has any insights to that I would be grateful.
For three displays, both Mini DisplayPort adapters must be active. VGA and Dual-LinK DVI adapters are always active, but most single-link DVI and HDMI adapters are not. If you replace your HDMI adapter with one that is active you should be able to use all three displays.
Yes to both. I am aware that the 5770 needs to be in th 16x lane. It was a stright replacement for the grpahics card that was in slot 1. It is better this morning - smoother and less sticky and clunky. Also the windows are now able to be dragged across to the second monitor. But it still isn't as smooth as the previous card and a little dissappointing performance wise - one would ahve hoped to notice an improvement rather than worry about a degradation....