How to make Link speed 2.5GT/s to 5.0GT/s on ATI card and Nvidia card

Discussion in 'Mac Pro' started by fouel, Feb 22, 2013.

  1. pastrychef macrumors 601


    Sep 15, 2006
    New York City, NY
    As far as I know, the soft straps are respected.
  2. MacVidCards Suspended

    Nov 17, 2008
    Hollywood, CA
    The way softstraps work has changed for each Nvidia family.

    Or, more accurately, for the sake of this thread, the location to turn on and off the PCIE 2.0 function has changed.

    I am not sure if Apple or Nvidia dictates these changes, but they certainly make things difficult to find.

    Every time it has been brute force, change, flash, test. Frequently several dozen attempts before it is found.

    Netkas has used IDA to look at these roms but I always end up finding the PCIE 2 switch location through trial and error.

    Figuring out for Mac GT120 was tricky because there is no direct PC version of that EXACT card. So there is no direct A/B comparison to be made.

    Now if you get ahold of a PNY 9500GT that has been flashed and already works as Mac GT120, you just have to find the PC BIOS and see what got changed. Armchair genius.

    The softstraps used to set final nibble of device id for Nvidia cards. Since Fermi they are totally set by resistor as hardstraps. When they were set by softstraps it was necessary to keep checksum correct if changing device id. (You can turn a GTX260 into a GTX285 via both the device id in rom, and by softstraps with checksum)

    The person who started this thread has no idea what any of this means, he just reports what he finds when looking at finished result. He does not know how or why, just what was done.

    You need to read up at

    Netkas released the modified EFI for 7970 and instructions to make your own.

    Flashing has to be done in DOS or Windows.
  3. pastrychef macrumors 601


    Sep 15, 2006
    New York City, NY
  4. Jani81 macrumors member

    Feb 12, 2013
    One more question about this subject. I already have one 7970 "mac edition" bought from you and the question is can i copy that rom from your card to my radeon xfx 7970 card? I didn't get that card working crossfire configuration at windows with bootcamp so that's the reason why i want to make "mac edition" card from xfx card also because it's much more quiet and it have better cooling system. Or do you have any suggest how to get crossfire configuration work at windows with ati cards? When i put xfx card with your flashed 7970 card and crossfire cable windows doesn't boot at all. At osx it works when i try luxmark example(2200 points at room scene :cool:). Sorry about my bad english sometimes but i hope you understand even something what i write :D
  5. MacVidCards Suspended

    Nov 17, 2008
    Hollywood, CA
    What EXACTLY does "doesn't work" mean? Describe exact symptoms.

    Windows is very finicky when you add hardware. There are 50/50 odds that the rom will work. Does card have switch for backup rom?

    Isn't there another thread you started somewhere on this?
  6. Jani81 macrumors member

    Feb 12, 2013
  7. Inconsequential macrumors 68000

    Sep 12, 2007
    Just modded my 7950 to 5 GT/.

    Card is a HIS 7950 IceQ Boost. 925/1250 stock clocks.

    Small increases in performance at 1000/1500 which is what my 7950 BIOS is flashed at.
  8. Spacedust macrumors 6502a

    May 24, 2009
    I found many users have modded Sapphire Vapor-X HD5870 to 5.0 GT/s. How it was done ?
  9. aroncz macrumors newbie

    Apr 30, 2012
  10. torvin macrumors newbie

    Dec 10, 2013
    Could you please post the exact model of your card? I am looking at an HIS 7950 IceQ Boost on newegg and I want to make sure it's EFI-flashable and R17-moddable... Thanks in advance.
  11. Inconsequential macrumors 68000

    Sep 12, 2007
  12. torvin macrumors newbie

    Dec 10, 2013
    Nice. I was looking at the same card. Let's hope it's back in stock soon.

    So, after flashing that card with an appropriate BIOS/EFI file and removing resistor #17, you get a mac boot screen and you get 5.0 GT/s. Am I correct? If so, could you kindly point me in the right direction for the exact BIOS/EFI file you used? I am a bit worried and I wouldn't want to brick a $300 card. I know the original BIOS should be backed up just in case. Thanks in advance once again.
  13. Inconsequential macrumors 68000

    Sep 12, 2007
    I modified my own based on my cards BIOS and clocking ability so there is no guarantee it will work on yours too. (ASIC quality!)

    See netkas forums for pre-made bios files. I'll see if I can find the link to one that I found.
  14. Cecco macrumors member

    Jun 11, 2008
    That is the exact same card I use in my Mac Pro since April.

    It pushes hot air out of the case the same way the Mac version does, but the card is slightly faster and quieter due to the better cooler.

    It doesn't block PCI Slot 2 at least not for shorter PCIe cards, what many other 7950 cards do. A full length card in slot 2 won't fit though, as the fan is slightly raised.

    IMHO the best 7950 card you can get for you Mac Pro, if you are concerned about fan noise.
  15. CrazyNurse macrumors regular

    Oct 23, 2012
    NEWB Question

    What is the purpose of the resistor i.e. why is it there in the first place if it's hindering the link speed?

    Is there some danger running at 5.0GT/s that the card makers are trying to protect us from?

    BTW: I recently flashed my PC XFX 7950 and am a very happy camper now that I can see my boot screens.
  16. stmp macrumors member

    Jul 17, 2012
    Resistor Trick on other 7xxx models

    First of all, thanks to all for providing the community with this useful info.

    Has anyone experimented with removing the R17 resistor on any other model 7xxx GPUs?

    Two specific Questions:

    1) Looking specifically at 7750, 7770, any manufacturer. Realize that the resistors on these other models may well be way too different than the 7950 but figured it's worth asking here.

    Hoping to get a single slot 7xxx GPU for a cMP and have it run at 5.0 GT/s.

    2) On a similar note, and apologies since someone already asked on Netkas, but has anyone figured out how to enable 5.0 GT/s on any of the newer versions of these GPUs, specifically the R9 280X? That seems to be the most powerful dual slot AMD card that will run on the cMP but not sure if anyone has it going at full speed 5.0 GT/s. Wonder if anyone popped the correct resistor off to enable full speed.

    Thanks much for any help with this!
  17. Yidahoo macrumors newbie

    May 1, 2013
    5.00 GT/s in X-Plane

    I have just popped the resistor on my 7950, partly due to the fact I always felt it was under performing in X-Plane 10. Frame rates were generally good but when the scenery got complex, it started to bog down.

    It seems that the link speed is very significant to X-Plane as having removed it, the frame rates are up maybe 20%, but more importantly I can display significantly more complex scenery before it starts to bog down. I can only assume that 2.5GT/s will not shift scenery quick enough.

    Now a very happy virtual pilot.

    FYI I am on a 4,1 Mac Pro flashed to 5,1 running an i7 990X. 12GB Ram and a base level MSI 7950 with 3GB VRAM
  18. pinktank macrumors 6502

    Apr 5, 2005
    Hey all, I have a GV-R795WF3-3GD, which seems like it follows the reference as far as the resistors go, so would I just pop r17?


    Hey all, I have a GV-R795WF3-3GD, which seems like it follows the reference number 2 as far as the resistors go, so would I just pop r17 and flash a bios for it to become the mac edition?
  19. vanden macrumors newbie

    Oct 4, 2011
    I have a Mac Pro 2008 and HIS HD 6850 IceQ X Turbo graphic card.
    I have no resistor in R3, on my HD6850, I recovered a resistor (10K) on a dead card, but impossible to weld !
    The resistor is really too small !
    But I tried with a pen with conductive ink : it is ok :)

    This problem (PCIE Link speed @ 2.5GT/s) also affects PC SAS controller PCIE 2.0 ? Or other PC PCIE 2.0 Card (USB 3 for example) ?
  20. Spacedust macrumors 6502a

    May 24, 2009
    It shouldn't ;)
  21. flyingweasel macrumors newbie

    Aug 3, 2014
    Thanks fouel & J-MI, amazing job no matter what MacVidCards may say. MacVidCards had time enough to take credit for it, too bad for him he saw only $$$ in his eyes. He even wants to shut your eyes, unbelievable, from netkas' forum: "Lighten up guys, it will be out soon enough. It's not like I can turn everyone's eyes off from a distance", give this kid a lolly please.

    Glad there are down to earth guys like netkas left, towards whom I am happy to send a donation.
  22. AppleTools macrumors member


    Dec 12, 2009
    Too many options!!!

    This is one of the most interesting threads I have ever read!

    Science! Adventure... Risk of death!!! (at least for the video cards) and even a little drama! :D

    I already digested all the info and decided to go for a 7950 for a 2008 8 core MacPro I picked at a bargain price on eBay... My question to all of you guys is which 7950 would be the best choice. I´ve seen many brands around so which one should I pick?

    Vortex, MSI, Gigabyte, XFX, Saphire, HIS, PowerColor...

    Which one is the best choice and why?

    Although I´m an electronic engineer I have to admit that I love the "pop" your resistor solution!

    So if anyone has a suggestion, It would be highly appreciated as I will be buying the upgrade soon.

    Thank you very much in advance...
  23. MacVidCards Suspended

    Nov 17, 2008
    Hollywood, CA
    Reference boards are the only ones with 4 outputs, most lose HDMI

    I would avoid HIS and XFX
  24. SHegner macrumors newbie

    Sep 20, 2014
    Hi Concorde,

    could you let me know what needs to be connected by the pencil? Does a conductive pen work as well?

    Thanks and kind regards,
  25. Spacedust macrumors 6502a

    May 24, 2009
    What about HD5770 or HD5870 cards ? There is still no answer here :(

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