Currently Being ModeratedMay 18, 2012 9:00 AM (in response to Richard Bryan)
Start with a PRAM Reset, which is supposed to rebuild the What-Hardware-Is-Where tables.Mac Pro (Early 2009), Mac OS X (10.6.8), & Server, PPC, & AppleTalk Printers
Currently Being ModeratedMay 18, 2012 10:26 AM (in response to Grant Bennet-Alder)
I did not expect this to have any effect, but I tried it anyways. No difference.
The PRAM is non-volatile hardware memory which is accessed by the machine independent of whatever OS is used. If it is working for one OS, I would not expect the other OS to have problems with it. In any case, it is read before booting, before the machine even knows which OS it is going to boot from.
The problem is clearly related to MacOSX 10.7, not the hardware.
Currently Being ModeratedMay 18, 2012 10:40 AM (in response to Richard Bryan)
@Richard - have you checked the mirroring settings in your System Prefs | Displays ?
It looks like you have mirroring turned on in 10.6 but not 10.7:
Main Display: Yes
For what it's worth, I'm using dual displays on 10.7 with the HD 5770.
Currently Being ModeratedMay 18, 2012 10:45 AM (in response to Richard Bryan)
Resetting the PRAM is so easy to do, that it is worth a shot anyway. Occasionally the form of what is stored there has changed between versions, and it is not unheard of for a PRAM Reset to solve a problem like this one.
Sorry that was not THE solution.Mac Pro (Early 2009), Mac OS X (10.6.8), & Server, PPC, & AppleTalk Printers
Currently Being ModeratedMay 18, 2012 10:45 AM (in response to mindlube)
I'm suspecting there may be something wrong with the 5770 card, I'm running a 30" plus two 24"s off this card with no issues.
Currently Being ModeratedMay 18, 2012 11:40 AM (in response to mindlube)
I can not turn mirroring on because the second (and 3rd, for that matter) output is not even detected. The machine thinks there are no external displays available for mirroring. Clicking the Detect Displays button does not change this.
Just a reminder, it works fine when booted from 10.6. It does not work when booted from 10.7. This proves there is no problem in the hardware.
Currently Being ModeratedJun 28, 2013 12:06 PM (in response to Grant Bennet-Alder)
Forgive the length of this, I wanted to add this as, over a year after its original posting, reading the above solved my problem.
Here's the situation; I just bought a used MP 3,1 to be able to catch up on new OS generations. I moved my hard drives, additional RAM and the 5770 from my original MP 1,1. into the new (to me) machine. OS for both is 10.7.5.
I ran my three displays as I had on the 1,1. A 20" Cinema Display via a MDP on the 5770 and Apple's passive MDP to DVI adaptor. A 23" Viewsonic via the DVI port and a second 20" Cinema Display via an Arkview USB to DVI converter. All worked fairly well on the MP 3,1 as they had on the MP 1,1.
For a week.
And then, in the spirit of upgrading fervor and after much reading on these forums, I bought 2 - Accell MDP to DVI Active adaptors. I reconnected the displays with the 2 Cinema Displays going through the new adaptors and the Viewsonic staying in the DVI port. Powered up...nothing.
Well, the opening chime and then 1 display showing a blank gray screen...no Apple logo, no spinning "gear". Switching adaptors between monitors just shifted which display had the gray screen. Reducing to 2 and then a single monitor...the same. Pulling the 5770, blowing it with canned air, cleaning the card contacts and reseating firmly, nada. Restoring back to the original configuration and adaptors also unsuccessful.
Then I came back to these forums on my iPad and finding this thread ended up agreeing with Grant above...resetting the PRAM "it is worth a shot". I zapped the PRAM (a couple of times), reconnected using the Accell adaptors, hit the power switch and went to make a much-needed drink. When I returned there was a much-welcomed apple logo and spinning "gear". The boot process was unusually long and the displays had to be re-mapped vis System Preferences but all displays were working and continued to do so through several re-boots.
Conclusion; while I can not definitely prove resetting the PRAM solved the problem, it was the one attempted solution that resulted in restoring the displays. My thanks to all who contribute here.
Currently Being ModeratedJun 28, 2013 12:40 PM (in response to William Etter)
Resetting NVRAM helps which happens on a cold restart when you "zap PRAM' as well as when SMC is reset.
Corrupt NVRAM use to happen more often on G5 and earlier OpenFirmware PowerMacs. And, whenever hardware changes were made, RAM and PCIe or even change of SATA drives, it was pretty much a given that nvram device tree had to be forced to be rebuilt. Less or not so with Intel or with older Motorolla G4s.
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