Q: 2009 Mac Pro will not boot with the Apple 27" LED Cinema Display

Hi there. Yup. having no problem with my Radeon 7950 (sapphire card) . However, I'm using an Apple Cinema Display with DVI.  there has been a previous posting from someone else, which mentions that he's having problems with stuff attached to the DisplayPort with 10.9.2. sorry, I know, this doesn't help you at all.

I think your assumption is correct

JB

I may have at least a partial answer for you.

Important question is....when you boot and look in system profiler at "About This Mac" is the 7950 id'd as "AMD Radeon 7xxx" or "AMD Radeon 7950"?

I just recreated your problem, quite repeatable, but only when the rom switch is in PC position, ie booting via self initing drivers.

If in the EFI position, it works fine. I have a 24" Apple LED and a 27" Apple LED running 10.9.2.

It is bad enough in PC position that just connecting the Apple Display causes machine to crash and reboot.

Doh!

Yea, my switch is in the wrong position too!

I'm off to bed but will try the fix in the morn and report back.

(You'd of thunk that the Radeon 'Mac version' would come with the switch in the correct position...

and that if it worked in 10.9.1 then all was fine. )

Many thanks DPart!!!

Just a heads up, but I'm also using the Sapphire HD 7950 Mac Version and was having the exact same problem; i.e., Mac Pro refusing to boot after upgrading to 10.9.2.

Upon checking my graphics board, the switch was in the proper position (the right side, default position) for a Mac.  I reinstalled an older graphics card and checked "About This Mac" and the graphics board designation was "HD 7xxx," so I decided that it wouldn't hurt to try the 7950 with the switch in the other "incorrect" position.

Bingo, my Mac Pro (early 2009) boots and "About This Mac" says that the graphics board is the "HD 7950."

So, I can only conclude that there is some kind of manufacturing glitch with the Sapphire HD 7950 Mac Version (wrong switch? lines crossed?) or that there is a misprint in the installation manual.

Same here......not sure whether my situation is a Sapphire manufacturing or Apple combo update tweak.

Sorry, Dave.....my situation is the same as yours, with the switch set to the Mac position I have no issues....I was thinking aloud as to whether my card might be a later Sapphire manufacturing run that addressed possible backward wiring or whether Apple did a behind the scenes software tweak....

Our Sapphire 7950 Mac edition here at the office has been working fine, even with the latest OSX update.  Stumbling across this thread though made me check system profiler to see what it said.   Sure enough it listed 7xxx and not 7950, even though on visual inspection (and checking, comparing to what the manual said) the little switch was supposedly in the Mac position.  Shutting the MP down, moving the switch to the "PC" setting and restarting the machine it's now shown as "7950" in system profiler.   Guess the wiring was odd.  For the record in either position the machine was working fine though (which is why I never bothered to check).

/edit   We bought this card late last summer, maybe in August.   Of note: A second one purchased in January had performed much worse then the original. This one does have the switch wired correctly and shows 7950 in another MP.  The 2nd newer card seems to be of a lower performance tier.

Out if curiosity, is the lower performing card In a 3,1 (2008) Mac Pro? Look in System Profiler under "model identifier"

I have found that since 10.9 the 3,1 Mac Pros have taken a 35-40% performance hit relative to ALL the other models.

By using the Tiamo mod I was able to see that even 1,1 Mac Pro is unaffected.

Very odd and disappointing.

I am glad that my post has been able to help so many people.

I would not say that the switch is mis-wired, as the wiring is laid out optically on PCB. The chips just got put on wrong spots. There are two SOIC-8 EEPROMS. They must just have gotten the positions switched.

It is even possible that the cards are low enough production that they flash each one by hand, in which case a bored employee just flashed And tested but never looked which position the switch is in.

In our lab we 20+ mac pros 4,1 7950 installed no problems.

Chipset Model:          AMD Radeon HD 7950

  Type:          GPU

  Bus:          PCIe

  Slot:          Slot-1

  PCIe Lane Width:          x16

  VRAM (Total):          3072 MB

  Vendor:          ATI (0x1002)

  Device ID:          0x679a

  Revision ID:          0x0000

  ROM Revision:          113-E2080C-101

  EFI Driver Version:          01.00.624

Correct!  The machine with the lower performing card is in fact a 2008 MacPro (3.2Ghz, 16GB ram.)  I was planning on swapping the cards to see if it mattered but in the mean time put the 5870 back into the 2008 which seams to have the same performace as the 7950 I mentioned. 

The other MacPro is in the middle of a major project and I don't want to rock the boat until it's done being used.  It's a 2010 MP 8 Core 2.4Ghz machine (16 threads). 

I'll swap them around in a week or so to see if it makes any difference.