4,1 / El Cap / Flashed 7950 / DP 1.2 boot problem

Discussion in 'Mac Pro' started by bookemdano, Apr 2, 2016.

  1. bookemdano, Apr 2, 2016
    Last edited: Apr 2, 2016

    bookemdano macrumors member

    Joined:
    Jul 29, 2011
    #1
    I recently bought a 4,1 single CPU and did many of the usual upgrades (X5670, 24GB 1333MHz RAM, SATA SSD, 802.11ac+BT4.0 card). My impetus for doing all of this is I had recently purchased a Seiki Pro 4K 40" monitor (note it is a proper SST 4K monitor, not one of their TVs) and my old 2010 Mac Mini couldn't do 4K at all. I almost bought a 2012 or 2014 mini but the fact that they can only do 4K @ 30Hz led me down the cMP rabbit hole.

    Overall I'm very happy with my decision. But here's the problem I'm having:

    I bought a Gigabyte Radeon 7950 GV-R795WF3-3GD rev 2.0. I was able to get it for about $150 and prefer the 3-fan design to the one fan on the reference card. Port layout is identical to the reference (2 mDP, 1 HDMI, 1 DVI). I did a ton of research about flashing it over at netkas and had no problems adding the Mac EFI to the BIOS and flashing it to the card. Did all of that on a windows machine and the card works perfectly.

    But my problem is I cannot get the Mac Pro to boot if my Seiki Pro monitor is connected to the card via DP AND the monitor is set to DP 1.2 mode. I hear the power-on chime and the fan speeds up. I get a garbled screen on the monitor and the MP doesn't boot. Behavior is similar if I used the second mDP port on the card, with the exception of the startup chime repeats like a stuck vinyl record (bingbingbingbing...).

    If I leave the DP cable disconnected, turn on the Mac Pro, wait for the chime and then plug in the DP cable, the Mac boots just fine and DP 1.2 is fully enabled once I log in (it's doing 4K @ 60Hz).

    Or if I change the displayport setting in the monitor menus to 1.1 everything works perfectly. The Mac boots, I see the boot screen, etc. But I'm limited to 30Hz. Once booted I could use the monitor menu to change the DP mode back to 1.2 and then I can jump to 60Hz but that takes about 10 button presses on the monitor each time--would get old fast.

    The DVI port works fine too--but of course with the same limitation of 4K @ 30Hz. But that only works if I do not also have it connected to mDP.

    If I use the BIOS switch on the card to go to the other position (which still has the stock BIOS and PC UEFI) the Mac Pro will boot just fine with the monitor set to DP1.2 and with the DP cable connected the whole time (just no boot screen and once booted the card uses the generic framebuffer).

    I've tried SMC and NVRAM resets. I've also tried four different displayport cables (including two certified 1.2 DP->mDP cables and a regular DP->DP cable with a DP-mDP adapter). Behavior is the same with all of the cables.

    Having done plenty of research on this beforehand, I was prepared for the fact that I likely wouldn't get a boot screen with DP1.2. But I was not at all expecting a situation where my monitor would actually prevent the Mac from booting period.

    I plan to try to contact Seiki to see if this is some kind of bug with their monitor. But I also wanted to post here in case anyone has seen this kind of issue before and had any ideas.

    Thanks!

    Edit: Unfortunately I don't have another 4K DP1.2 monitor available to test, nor do I have access to another 7950.
     
  2. h9826790, Apr 2, 2016
    Last edited: Apr 2, 2016

    h9826790 macrumors 604

    h9826790

    Joined:
    Apr 3, 2014
    Location:
    Hong Kong
    #2
    I don't think you can't get boot screen in 4K with the 7950.

    For daily use, PC BIOS should be fine (unless you need HDMI audio (which also enable audio via DP). Keep the switch at there, and only use EFI boot (with monitor set to DP1.1) when needed may be an easier way to deal with this setup.
     
  3. bookemdano, Apr 2, 2016
    Last edited: Apr 2, 2016

    bookemdano thread starter macrumors member

    Joined:
    Jul 29, 2011
    #3
    Thanks for the reply. Well what's confusing is I absolutely can get a 4K boot screen on mDP with the card in EFI mode, but only if the monitor is set to DP1.1 (and thus the boot screen is @ 30Hz).

    But I've not seen anyone else report an issue where the cMP won't even boot at all with a DP1.2 4K monitor connected. That's what makes me curious about what the culprit is.

    And I was hoping to get audio over mDP working, which evidently I cannot do with the BIOS switch in the PC mode. It's my best option for now, but this problem still troubles me because I seem to be the only one experiencing it.

    Edit: Just to clarify--on a brand-new, stock PC 7950 there's zero difference between the two positions of the BIOS switch right? In other words it switches between two identical flash ROM chips. My understanding was that the purpose of that switch is just to give you a rescue back to the stock BIOS if a flash goes awry. So the fact that I flashed the card with the switch in the position away from the bracket doesn't really matter, right? That was my understanding, anyway. But just thought I'd make sure.
     
  4. h9826790 macrumors 604

    h9826790

    Joined:
    Apr 3, 2014
    Location:
    Hong Kong
    #4
    I can get the boot screen on my 4K TV via HDMI, but TBH, I don't know if the Apple logo is 1080 or 4K. I did that long time ago, and didn't try to go into recovery partition to verify it. But once I boot to desktop, it's 4K 30Hz.

    And AFAIK, 7950 cannot get boot screen on 4K 60Hz, but I don't know if that will cause unable to boot.

    If you really need EFI boot, the simple work around may be just keep the monitor off until the Mac Pro finish the initial boot process. That's easier than keep switching between DP1.1 and DP1.2.
     
  5. bookemdano thread starter macrumors member

    Joined:
    Jul 29, 2011
    #5
    Yeah thanks. Unfortunately a soft-power off/power save mode is not enough--the Mac Pro still won't boot. I have to unplug the monitor power cord (or DP cord).

    Just can't believe achieving 4K SST 60Hz is this troublesome. And I'm frustrated because I seem to be the only one with this problem and no way to isolate the cause (if it's maybe a quirk with that particular Gigabyte card or some handshake issue with that particular 4K monitor). If I knew whether a different 7950 card would work better I'd probably drop another $150 on it just to make this problem go away. But it would suck to spend the money and then have the same problem occur with the new card.

    Anyway, if anyone else knows anything about this I might have missed I'd be much obliged.
     
  6. h9826790 macrumors 604

    h9826790

    Joined:
    Apr 3, 2014
    Location:
    Hong Kong
    #6
    Then how about get a DP switch? Put that in a convenience place, and switch to the no connection port when boot, switch it back to the monitor after boot? It will cost you a bit, but that should have the same effect as unplug the monitor.
     
  7. Fl0r!an macrumors 6502a

    Joined:
    Aug 14, 2007
    #7
    I don't think your problem is uncommon, Mac EFIs don't like DP 1.2.
    Just use the card unflashed, you won't get a boot screen anyway.
     
  8. thevidness macrumors newbie

    thevidness

    Joined:
    Nov 1, 2013
    Location:
    Berlin, Germany
    #8
    i have a 5,1 with an original sapphire radeon 7950 mac edition (the white one) with a lg 27MU67-B SST 4K display, also running on dp 1.2. i have the exact same problem. the system hangs if the screen is connected and switched on at boot.

    my solution involves a secondary display which is connected to the dvi port. during boot i power off the 4K display, letting the boot screens appear on the secondary display. when i see the os x login screen i switch it back on and everything is fine.

    this situation is unfortunate but is most likely unfixable, as far as i can tell.

    best regards.
     
  9. bookemdano, Apr 6, 2016
    Last edited: Apr 6, 2016

    bookemdano thread starter macrumors member

    Joined:
    Jul 29, 2011
    #9
    Thanks everyone for your input. Sounds like there's nothing that can be done and all 7950s suffer from this problem.

    It's been bugging me enough that I've decided to go with a GeForce 750 Ti and get it flashed. Having to install web drivers is an annoyance but not as much of an annoyance as jumping through hoops every time I reboot. I'll probably keep the 7950 around for times when I need to use FCPX and want decent acceleration.

    Hope this thread comes up in a search for the next person thinking of buying/flashing a 7950 to use with a 4K SST monitor over DP1.2. I'm still really surprised there aren't more posts about this issue. I did tons of research on this before going with the 7950. Had I known about this issue beforehand I wouldn't have bought it.

    Thanks again guys for the help.
     
  10. h9826790 macrumors 604

    h9826790

    Joined:
    Apr 3, 2014
    Location:
    Hong Kong
    #10
    If you pick the 750Ti that only need power from PCIe slot, you can use that with the 7950.

    Also, for your info, there is only one reliable source to get the flashed 750Ti. And you can't flash it by yourself.
     
  11. bookemdano thread starter macrumors member

    Joined:
    Jul 29, 2011
    #11
    Yeah I was going to try to see if I could run both cards. And yes I am having that reliable source flash my 750Ti :)

    Thanks for all your help h9826790
     

Share This Page