Our blog has been buzzin’ with questions as to whether or not the new Radeon 5870 and 5770 video cards found in the new Mid 2010 Mac Pros work with earlier model year Mac Pros. When first asked about this, we referred to the Apple display page that conspicuously left out any model except 2009-2010 Mac Pros

Fanning the flames of desire for more knowledge/information on this subject was Rob-ART at BareFeats who did confirm a day or so ago that the Radeon 5870 does work with 2008-2010 Mac Pros.

So we dove in deeper to give all inquiring minds a full blown investigation you have come to expect from us. Here’s the breakdown:

2006-2007 Mac Pro:

Sorry to say it, but the 5870 is not…repeat… NOT compatible.

compatible. The 5770 is compatible, but only with the DVI connection.

2008 Mac Pro:

Both the 5870 and 5770 cards work with both the DVI and MiniDisplay Port connections in any combination of two displays. So, you can have two displays with MiniDisplay connections, or one with a DVI connection and one with a MiniDisplay connection.

Adding a third display will override the DVI connection, causing it to deactivate.

2009-2010 Mac Pro:

Both the 5870 and 5770 cards work with both the DVI and MiniDisplay Port connections in any combination of two displays. So, you can have two displays with MiniDisplay connections, or one with a DVI connection and one with a MiniDisplay connection.

Adding a third display will override the DVI connection, causing it to deactivate.

We have also confirmed that all NewerTech Mini DVI and MiniDisplay Port video adapter cables are compatible with all Mac Pro models. And that’s a good thing as they offer thicker cabling and better shielding for the highest quality, interference-free display output.

Speaking of adapters…you are familiar with the NewerTech USB to DVI/HDMI/VGA to Video Display Adapter? You know, the one that lets you add up to four additional monitors to your Mac? A very cool gadget that’s bus powered so its ideal for mobile presentation use as well.

So there you have it…what cards you can add to your existing Mac Pro…what cables you use for a higher quality display…and more display space overall. A visual trifecta!

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UPDATE 8/27/10 Well, a bit clarification on certain issues and reiteration of others…here’s what we discovered after additonal testing (and yes, some of your feedback):

Despite using a boot drive from a Mac Pro 2010 model, we still could not get the 5870 to work with a 2006-2007 machines. We tried both 1,1 and 2,1 machines with most up to date boot ROM and SMC versions. And were running 10.6.4 with all current Apple (AAPL) updates installed.

The 5770 in the 2006-2007 is compatible using the newest build of 10.6.4 which is included with the new Mid 2010 Mac Pros and allows you to take advantage of all three display outputs on the 5770.

The 5870 and 5770 are fully compatible with 2008 Mac Pros using the newest build of 10.6.4 (which again is included with the new Mid 2010 Mac Pros) and allows you to take advantage of all three display outputs on both video cards.

We incorrectly stated that you could only use two displays on the 2009-2010 Mac Pros. In reality, all three display connectors can be utilized simultaneously so you can drive three displays.

We will continue to investigate all these issues (esp. the 2006-2007 models) and update the findings here accordingly. Thanks for your patience while we sorted this out! Now, we gotta get back to making some eSATA equipped iMacs and the OWC SSDs going into them as well ;-)