Mac Pro 5.1 + GPU Upgrade + BOOTCAMP + WINDOWS 8.1/10

[MikkelAD]

Hey Guys

I have been looking for a GPU upgrade for some time to replace the stock ATI 5770.

I looked for: 980, 980 TI, 780, 780 TI and cards in that range but don't want to spend to much money since I don't need a "strong" GPU for professional work or something like that.

In my research I came across Geforce GTX 680 and saw threads on diffrent forums about flashing it yourself for EFI (boot screen).

In threads like:

https://forums.macrumors.com/threads/confirmed-and-possible-flashable-gtx-680-models.1578255/

People list SOME of the models of the GTX 680 and here is my question...

Does anybody know if it is possible to flash this model of the GTX 680 ? ? ?

https://www.evga.com/products/Specs/GPU.aspx?pn=67e14569-9b25-4ebe-88f9-b6b7a66cb995

Part number: 02G-P4-3684-KR

Thanks in advance !

 

[ActionableMango]

If you do a forum search for "02G-P4-3684-KR", you will see that it is a verified card.

Even if it wasn't verified, almost all 680's flash fine. Just a very few weird exotics so far have not flashed well.

 

[fendersrule]

Any reason why you'd want a GTX 680 over a 7950?

 

[bsbeamer]

I find that typically, many of the "standard" style EVGA cards work fine with Mac and NVIDIA drivers. Would avoid Zotac GPUs if wanting to use with Mac. Have personally run into issues with their GTX 680 variations in the past. Always good to find as close to a reference design as possible.

 

[MikkelAD]

If you do a forum search for "02G-P4-3684-KR", you will see that it is a verified card.

Even if it wasn't verified, almost all 680's flash fine. Just a very few weird exotics so far have not flashed well.

Yeah okay I didn't see that thread when I searched google before :S
[doublepost=1520276256][/doublepost]

Any reason why you'd want a GTX 680 over a 7950?

Not really... I know they are pretty much the same performance wise and as far as I could tell from diffrent forums the 7950 should be flash-able too.

I just came by this GTX 680 in my country listed at 115 USD so thought it was pretty cheap...
[doublepost=1520276319][/doublepost]

I find that typically, many of the "standard" style EVGA cards work fine with Mac and NVIDIA drivers. Would avoid Zotac GPUs if wanting to use with Mac. Have personally run into issues with their GTX 680 variations in the past. Always good to find as close to a reference design as possible.

Yup. Seems to always be the best idea...
[doublepost=1520276787][/doublepost]I have thought about diffrent GPU's and to be honest I kind of want something like 980, 980 TI, 780, 780 TI but they seem to be pretty expensive at ebay often sold for 330-420 USD and it's rare to find a flashed card :S

Plus the last flash-able card (by yourself) was 680 GTX... Like I said before opportunities http://www.macvidcards.com is not relevant to me...

 

[ActionableMango]

That is a decent price. If you buy the GTX680 and want to flash it, there are step-by-step instructions for doing so that are linked in my signature.

Also, welcome to the forum.

 

[MikkelAD]

That is a decent price. If you buy the GTX680 and want to flash it, there are step-by-step instructions for doing so that are linked in my signature.

Also, welcome to the forum.

Yup and maybe I can get it a bit cheaper. Thank you for the link, but let us be real a 980 GTX would look beautiful in my little baby - So sad flashing cards kind of stopped at 680 GTX unless you use macvidcards...

 

[bsbeamer]

There hasn't been an official GTX Mac card released since the EVGA GTX 680 for Mac. Think that has a lot to do with why there are no widely available flashes for 7XX, 8XX, 9XX, and 10XX at the moment.

 

[MikkelAD]

There hasn't been an official GTX Mac card released since the EVGA GTX 680 for Mac. Think that has a lot to do with why there are no widely available flashes for 7XX, 8XX, 9XX, and 10XX at the moment.

That is also my conclusion after reading hours and hours online the last months The GPU was kind of the last thing I would "mess" with since everything else is upgraded W3690, SDD, 32 GB RAM...

But guess it's 680 GTX or live without boot screen and the other problems :S

 

[fendersrule]

I'd seriously consider the 7950 over the GTX 680, and I say that as an Nvidia fanboi. It's "flash-ability" is just as good. I sold one on Craiglist with original box for $80 a few months ago. Oh yeah, they also almost always have dual roms, so there's very little, if any risk, if you really care about having a boot screen.

The 7950 is more future proof and the GTX 680 (based on old and abandoned Keplar architecture) fizzed out like a dried fart a long time ago and was abandonware to Nvidia when it came to future optimizations. The 7950 gives you 1GB of additional VRAM (3GB vs 2GB) which again, is more able to keep up with even some current games at higher resolutions. My 7950 drove several "newish" games at maxed 1440p with ease (Dirt 3, LFD2, TF2, any Indie Game I threw at it, and even Vermintide). Easily over 60 FPS in many cases, while Vermintide was 30-60 FPS depending on the map/location. Hell, if you have a stout Mac Pro with a 7950, you'll be able to hit 50-55 FPS in Doom mostly maxed @ 1440p.

The GTX 680 was dead long ago. Take a look at "how it performs 5 years later" benchmark sites, and you'll see the 7950 single-handedly pounces the GTX 680 in almost every game. When they were both brand new, they were pretty tit-for-tat when it came to performance. But in 2018? The 7950, hands down. The 7950 aged like a fine wine and the GTX 680 was like an opened craft beer that sat on the table and went stale.

 

[ActionableMango]

I'd seriously consider the 7950 over the GTX 680

I don't know about gaming, but I think FCPX also works better with AMD.

But why specifically a 7950? Aren't the 7970, R9 280, and R9 280x just as flashable, also have 3GB of ram, and either all faster and/or newer?

Also IIRC, XFX should be avoided when picking an AMD solution for Mac Pro.

 

[fendersrule]

I'll let H98 speak to the other models; I'm a noob. The R9 280 = 7950, so either works. AFAIK, the 280/7950 is plug and play, no flashing required since it's naively supported (minus boot screens). I'm not sure if you can take a 7970/280x and plug it into a Mac Pro without any flashing. Hopefully that can be answered. Edit: Looks like H98 already answered this previously, and the answer is "yes":

https://forums.macrumors.com/threads/sapphire-hd-7970-and-2009-mac-pro.1956674/#post-22576686

The 7950 I recommend because it's generally cheap (circa $80) and it works golden OOTB. You can also get pretty darn close to 7970 numbers with an overclock (which the 7950 so easily likes). But a 7970 would be great too!

Either way, don't pay over $80 for these old cards! I just wanted to chip in and say that the GTX 680 is inferior to the 7950/7970 in today's games/resolutions. Here's a good "revisited" comparison that had these cards battle each other with modern games and modern resolutions:

https://babeltechreviews.com/hd-7970-vs-gtx-680-2013-revisited/3/

It's the additional VRAM that really helps!

 

[MikkelAD]

Just to clarify. If I pull the trigger and buy something like 980, 980 TI, 780, 780 TI because I also like a bit of a challenge I will have the following "problems":

1) No Apple boot-screen because the card isn't flashed (Will have to use start-up disc to switch between OS)

2) Have to be patient about OSX and NVIDIA driver updates - Every time there is a new OSX and NVIDIA update I will have to go trough the same "show" again and again by:

A) Unplugging "new" NVIDIA GPU switch back to my stock 5770 B) Update OSX and NVIDIA driver C) Plugging the "new" NVIDIA card back in and hope for the best

3) Only PCI-E 1.0 speed in windows and NOT 2.0 because the card isn't flashed - So performance will be 5-10% slower... (Apparently NVIDIA cards care less about 1.0 vs 2.0 than Radeon/ATI from what I can understand)

Anything I have forgotten?

 

[bsbeamer]

The NVIDIA web driver update process is actually really easy if you have another machine that can connect through VNC or Apple's built-in screensharing. I setup 5,1 for remote access from my MacBookPro and basically can connect and see the desktop after every macOS update, even though the screen "isn't working" on the monitors connected to the machine. Easy to install the NVIDIA updates from there and usually download the installer file and place it on the desktop ahead of time. After system restart, everything works fine again. Just keep my EFI card handy in case there's an issue (official GTX 680 for Mac) or some unexpected change.

Unless things have recently changed, you will need to turn FileVault OFF if you have it enabled. Also helps with reliability if you boot directly into a user account on the 5,1. There are currently some issues with SIP being enabled/disabled and would recommend enabling if possible (or else enabling for updates). Overall it's really not a big deal for the majority of people using non-EFI GPUs.

It seems the biggest issues are when people install updates on machines before the drivers are released, or on machines that have the device ID's changed. With authentic 5,1 you should not run into that if you have some patience.

 

[MikkelAD]

The NVIDIA web driver update process is actually really easy if you have another machine that can connect through VNC or Apple's built-in screensharing. I setup 5,1 for remote access from my MacBookPro and basically can connect and see the desktop after every macOS update, even though the screen "isn't working" on the monitors connected to the machine. Easy to install the NVIDIA updates from there and usually download the installer file and place it on the desktop ahead of time. After system restart, everything works fine again. Just keep my EFI card handy in case there's an issue (official GTX 680 for Mac) or some unexpected change.

Unless things have recently changed, you will need to turn FileVault OFF if you have it enabled. Also helps with reliability if you boot directly into a user account on the 5,1. There are currently some issues with SIP being enabled/disabled and would recommend enabling if possible (or else enabling for updates). Overall it's really not a big deal for the majority of people using non-EFI GPUs.

It seems the biggest issues are when people install updates on machines before the drivers are released, or on machines that have the device ID's changed. With authentic 5,1 you should not run into that if you have some patience.

Well I have a 27" iMac late 2013 too That would probably work...

I have never used FileVault on any machines so that won't be a problem. Yup I heard about that SIP thing guess I just have to keep it it the back of my head if ever needed (guess I need to save the original DVD for recovery mode)

If I can skip any problems by having a "true" 5.1 from 2012 that would be great

! ! ! Another issue has arisen ! ! !

I upgraded my Mac with a Sonnet Tempo SSD for my two Samsung 850 Evo's. Therefore OSX recognizes my harddrives as external harddrives and I can't use Bootcamp :S

Thought I could just install Win 10 from a bootable USB like on a normal PC but if I get a new GPU I won't be able to boot into windows (no EFI and no Start-Disc Manager from bootcamp) or am I crazy ? ? ?

 

[orph]

was there problems with the GTX780 & 780TI with openCL apps? or something.
i know adobe did a fix at the time by disabling the thing that gave crashes i think (from hazy memory been ages)
the GTX970 might be a better value option over a 980 but i gess depends on price

the PCI speed thing will not matter and is same on ATI, think its only when you go past the GTX1080 it's starting to show?
so i think Titan V is the first card to show PCI 2 as to slow over PCI 3? (PCI 3 8 lane slot = PCI 2 16 lane slot i think?)

in osx thanks to not best optimized driver + osx graphics being dated you wont see it, in windows it will show more but id gess 90FPS v 92FPS wont be a problem

i use a GTX770 works fine but shows its age in games, the GTX9xx cards aged better i think? and use less power as a plus (less heat = less fan noise)

edit what do you want the gpu for games or work? that changes whats best a lot

for windows install
unplug all drives but the install drive (only 1 gpu)
then boot from the usb stick & install
once done shut down and stick all your drives back in
if your using osx10.13 with the new file system you may have problems

you may not be able to install windows on to a SSD on a PCI card (both my SSD's are in the top optical drive bay)

im using a GTX770 so i can use the native osx drivers so i dont know if it's different with a newer card.

edit 2
grim just looked at the cost of a GTX970 on ebay, they cost way to much for there age bitcoin

 

[h9826790]

I'll let H98 speak to the other models; I'm a noob. The R9 280 = 7950, so either works. AFAIK, the 280/7950 is plug and play, no flashing required since it's naively supported (minus boot screens). I'm not sure if you can take a 7970/280x and plug it into a Mac Pro without any flashing. Hopefully that can be answered. Edit: Looks like H98 already answered this previously, and the answer is "yes":

https://forums.macrumors.com/threads/sapphire-hd-7970-and-2009-mac-pro.1956674/#post-22576686

The 7950 I recommend because it's generally cheap (circa $80) and it works golden OOTB. You can also get pretty darn close to 7970 numbers with an overclock (which the 7950 so easily likes). But a 7970 would be great too!

Either way, don't pay over $80 for these old cards! I just wanted to chip in and say that the GTX 680 is inferior to the 7950/7970 in today's games/resolutions. Here's a good "revisited" comparison that had these cards battle each other with modern games and modern resolutions:

https://babeltechreviews.com/hd-7970-vs-gtx-680-2013-revisited/3/

It's the additional VRAM that really helps!

Yes, both 7970 and R9 280X is natively supported in macOS. In fact, it has exactly the same device ID as D700, just a different name. So, it should be OOTB as long as the nMP still supported by Apple.

However, AFAIK, the 7970 6GB version won't work on the cMP. Otherwise, it will be almost identical as D700 (without down clock).

It may be a bit tricky to power the 7970 / R9 280X. But basically same as my 1080Ti, as long as put a bridge between the mini 6pin and the card to balance the work load, the cMP should able to power it without issue. But if only use a single mini 6pin to power the 8pin, it can shut down the Mac under stress.

https://forums.macrumors.com/thread...inity-6-on-mac-pro-1-1.2105403/#post-25801466

If only consider VRAM, the 680 actually has a 4GB version which also flashable and work OOTB on cMP. But in macOS, the 680 can hardly go faster than the 7970 even has more VRAM due to software optimisation.

However, from MVC, it seems the 7970 has higher failure rate than other cards. So, this may be a concern.

https://forums.macrumors.com/threads/open-fan-gpu-or-fan-blower-gpu.1910174/#post-21745531

! ! ! Another issue has arisen ! ! !

I upgraded my Mac with a Sonnet Tempo SSD for my two Samsung 850 Evo's. Therefore OSX recognizes my harddrives as external harddrives and I can't use Bootcamp :S

Thought I could just install Win 10 from a bootable USB like on a normal PC but if I get a new GPU I won't be able to boot into windows (no EFI and no Start-Disc Manager from bootcamp) or am I crazy ? ? ?

It's much easier to install the Windows SSD in the optical bay. Just plug the SSD into the SATA cable, leave it there, done!

My SSD sits on the Super drive, but it's totally OK to hang it below the Super drive. I've done that for a long time.

I am using a non flashed PC 1080Ti, the Tempo SSD card, and I can dual boot between Windows and macOS. Simply keep using HFS+ in macOS (but not upgrade to APFS), then use system preference to select Windows, or in Windows using bootcamp apps to select macOS as next boot drive. So easy.

Also, for your info. You don't need any remote control, Mac EFI, or another GPU to do the macOS / web driver update. I shared the detail procedure in here.

https://forums.macrumors.com/thread...graphics-cards.1440150/page-173#post-25833765
[doublepost=1520365811][/doublepost]

Just to clarify. If I pull the trigger and buy something like 980, 980 TI, 780, 780 TI because I also like a bit of a challenge I will have the following "problems":

1) No Apple boot-screen because the card isn't flashed (Will have to use start-up disc to switch between OS)

2) Have to be patient about OSX and NVIDIA driver updates - Every time there is a new OSX and NVIDIA update I will have to go trough the same "show" again and again by:

A) Unplugging "new" NVIDIA GPU switch back to my stock 5770 B) Update OSX and NVIDIA driver C) Plugging the "new" NVIDIA card back in and hope for the best

3) Only PCI-E 1.0 speed in windows and NOT 2.0 because the card isn't flashed - So performance will be 5-10% slower... (Apparently NVIDIA cards care less about 1.0 vs 2.0 than Radeon/ATI from what I can understand)

Anything I have forgotten?

In these 4 options, IMO, the 980 is the best card if you don't need extreme power. 980 Ti require lots of power and may shutdown the Mac if you didn't power it correctly.

The 780 and 780Ti has much lower efficiency if compare to the Maxwell card. Even though they can work OOTB, but it doesn't matter because you have the 5770 on hand, and you can always swap it back in when require. No need to have an OOTB for day to day operation.

PCIe 1.0 or 2.0 is the very last thing I will concern. As long as you install the card in a x16 slot, the difference is very minimal. Also, it only affect performance when the bandwidth is saturated.

 

[MikkelAD]

Yes, both 7970 and R9 280X is natively supported in macOS. In fact, it has exactly the same device ID as D700, just a different name. So, it should be OOTB as long as the nMP still supported by Apple.

However, AFAIK, the 7970 6GB version won't work on the cMP. Otherwise, it will be almost identical as D700 (without down clock).

It may be a bit tricky to power the 7970 / R9 280X. But basically same as my 1080Ti, as long as put a bridge between the mini 6pin and the card to balance the work load, the cMP should able to power it without issue. But if only use a single mini 6pin to power the 8pin, it can shut down the Mac under stress.

https://forums.macrumors.com/thread...inity-6-on-mac-pro-1-1.2105403/#post-25801466

If only consider VRAM, the 680 actually has a 4GB version which also flashable and work OOTB on cMP. But in macOS, the 680 can hardly go faster than the 7970 even has more VRAM due to software optimisation.

However, from MVC, it seems the 7970 has higher failure rate than other cards. So, this may be a concern.

https://forums.macrumors.com/threads/open-fan-gpu-or-fan-blower-gpu.1910174/#post-21745531



It's much easier to install the Windows SSD in the optical bay. Just plug the SSD into the SATA cable, leave it there, done!
View attachment 753489
My SSD sits on the Super drive, but it's totally OK to hang it below the Super drive. I've done that for a long time.

I am using a non flashed PC 1080Ti, the Tempo SSD card, and I can dual boot between Windows and macOS. Simply keep using HFS+ in macOS (but not upgrade to APFS), then use system preference to select Windows, or in Windows using bootcamp apps to select macOS as next boot drive. So easy.

Also, for your info. You don't need any remote control, Mac EFI, or another GPU to do the macOS / web driver update. I shared the detail procedure in here.

https://forums.macrumors.com/thread...graphics-cards.1440150/page-173#post-25833765
[doublepost=1520365811][/doublepost]

In these 4 options, IMO, the 980 is the best card if you don't need extreme power. 980 Ti require lots of power and may shutdown the Mac if you didn't power it correctly.

The 780 and 780Ti has much lower efficiency if compare to the Maxwell card. Even though they can work OOTB, but it doesn't matter because you have the 5770 on hand, and you can always swap it back in when require. No need to have an OOTB for day to day operation.

PCIe 1.0 or 2.0 is the very last thing I will concern. As long as you install the card in a x16 slot, the difference is very minimal. Also, it only affect performance when the bandwidth is saturated.

Well I am searching, searching, searching and the GTX 970 crossed my path. I found this card:

https://www.gigabyte.com/Graphics-Card/GV-N970WF3OC-4GD-rev-10-11#ov

at the price of 200 USD and as far as I can tell that is a pretty good deal ? ? ?

I know it's possible to unplug one of my EVO's and connect it to one of the sata 2 ports. In fact I got 5 slots for it since my two evo's (on PCI-E CARD) are the only storage devices installed.

- Guess that will be my only option to plug one of them into sata 2 and accept the slower read/write speed (I know It won't impact my performance in general because IOPS will be the same - Right?)

That way boot camp should work but you say I will have a problem using APFS (already installed OSX that way) ? ? ?
If I remember correctly it's because bootcamp isn't supported together with APFS at the moment ? ? ?
[doublepost=1520369773][/doublepost]

Also, for your info. You don't need any remote control, Mac EFI, or another GPU to do the macOS / web driver update. I shared the detail procedure in here.

https://forums.macrumors.com/thread...graphics-cards.1440150/page-173#post-25833765

That is a thread about how to power a card probably and NOT remote control, Mac EFI.. ? ? ?

 

[h9826790]

Well I am searching, searching, searching and the GTX 970 crossed my path. I found this card:

https://www.gigabyte.com/Graphics-Card/GV-N970WF3OC-4GD-rev-10-11#ov

at the price of 200 USD and as far as I can tell that is a pretty good deal ? ? ?

I know it's possible to unplug one of my EVO's and connect it to one of the sata 2 ports. In fact I got 5 slots for it since my two evo's (on PCI-E CARD) are the only storage devices installed.

- Guess that will be my only option to plug one of them into sata 2 and accept the slower read/write speed (I know It won't impact my performance in general because IOPS will be the same - Right?)

That way boot camp should work but you say I will have a problem using APFS (already installed OSX that way) ? ? ?
If I remember correctly it's because bootcamp isn't supported together with APFS at the moment ? ? ?

Not sure if that 970 is a good deal, not very familiar with that card.

Correct, IOPS won't be affected.

Correct, bootcamp apps cannot see the APFS partition. Therefore, it won't let you choose the APFS macOS partition as the next start up drive. If you have an OOTB card, then you can just perform a PRAM reset, this will bring you back to macOS. However, if you use a Nvidia Maxwell / Pascal card, this is not a good option at all, because a PRAM reset will also revert your driver selection back to Apple driver, which means your 970 won't work at all until you select Nvidia web driver and reboot (this can be done via remote control).

TBH, it's much easier to just clone the existing macOS SSD to another drive. Format the SSD back to HFS+, then clone the macOS black from the backup drive. And then use the bootcamp apps.
[doublepost=1520369973][/doublepost]

That is a thread about how to power a card probably and NOT remote control, Mac EFI.. ? ? ?

This is the post about how to install macOS update and web driver WITHOUT remote control or Mac EFI etc.

 

[MikkelAD]

Not sure if that 970 is a good deal, not very familiar with that card.

I think that is one of the "better" 970 GTX models and 970 GTX performs pretty well...

https://www.videocardbenchmark.net/video_lookup.php?gpu=GeForce+GTX+970&id=2954

Correct, bootcamp apps cannot see the APFS partition. Therefore, it won't let you choose the APFS macOS partition as the next start up drive. If you have an OOTB card, then you can just perform a PRAM reset, this will bring you back to macOS. However, if you use a Nvidia Maxwell / Pascal card, this is not a good option at all, because a PRAM reset will also revert your driver selection back to Apple driver, which means your 970 won't work at all until you select Nvidia web driver and reboot (this can be done via remote control).

TBH, it's much easier to just clone the existing macOS SSD to another drive. Format the SSD back to HFS+, then clone the macOS black from the backup drive. And then use the bootcamp apps.

Yeah okay guess that's the way to do it. Do we know anything about the future in terms of APFS partition and BOOTCAMP ? ? ?

This is the post about how to install macOS update and web driver WITHOUT remote control or Mac EFI etc.

Now the thread worked probably and I got to the right post - Will keep that in mind.

Thanks for the answers so far!

 

[h9826790]

I think that is one of the "better" 970 GTX models and 970 GTX performs pretty well...

https://www.videocardbenchmark.net/video_lookup.php?gpu=GeForce+GTX+970&id=2954

Yeah okay guess that's the way to do it. Do we know anything about the future in terms of APFS partition and BOOTCAMP ? ? ?

Now the thread worked probably and I got to the right post - Will keep that in mind.

Thanks for the answers so far!

The GTX970 is a very safe bet indeed, very low power consumption, no need to worry about over stress the mini 6pins. Running at relatively low temperature, the fan may rarely need to spin up. And it seems 970 work very well with the macOS web driver as well.

No idea about what Apple will do. I don't think they really care about the bootcamp stuff. That's Windows, one of the very last thing that they want the users to touch.

 

[MikkelAD]

The GTX970 is a very safe bet indeed, very low power consumption, no need to worry about over stress the mini 6pins. Running at relatively low temperature, the fan may rarely need to spin up. And it seems 970 work very well with the macOS web driver as well.

Yup, that was kind of my conclusion too. I have read a lot of threads about powering different GPUs and the most safe way to power a card that requires 6-pin + 8-pin without a second PSU, pixal and all that crap is the following:

2 x mini 6-pin to normal 6-pin (from the board) --> A converter from two normal 6-pin to 1 x 8-pin

1 x 15pin SATA Power to 6pin

Correct ? ? ?

No idea about what Apple will do. I don't think they really care about the bootcamp stuff. That's Windows, one of the very last thing that they want the users to touch.

Well let's hope and cross fingers If I remember correctly BOOTCAMP has been updated from time to time so hopefully they won't just forget it. We need it to work probably more than ever

 

[Melbourne Park]

I want to have a driving sim, and can buy an Xbox or ps4, a PC, or put in a card and re-install windows 10 (which is not booting on my 5.1 mac which runs twin CPUs. I've got two fast clock rate four thread CPUs to replace my slow clock rate factory CPUs too. Not sure if the twin CPU macs will assist a game work in Win 10 ...

Can I run a PC driving sim like Assetto Corsa on my MacPro with its twin CPUs, and is GTX 970 or a 7950 fast enough compared to buying a PC with for instance a GTX 1050 card?

 

[h9826790]

Yup, that was kind of my conclusion too. I have read a lot of threads about powering different GPUs and the most safe way to power a card that requires 6-pin + 8-pin without a second PSU, pixal and all that crap is the following:

2 x mini 6-pin to normal 6-pin (from the board) --> A converter from two normal 6-pin to 1 x 8-pin

1 x 15pin SATA Power to 6pin

Correct ? ? ?

1) You only need a single cable (dual mini 6pin -> single 8pin), no need a cable combination for just a single 8pin.

2) single SATA only rated up to 55W, not good enough for a 75W 6pin. Since you have plenty SATA ports, you better go for dual SATA -> single 6pin

Anyway, for a 970, I am sure you can use my method to power it. The 970 is a relatively low TDP card, a 6+8pin config is just there for OC or under extreme demand. If the two mini 6pin can power my 1080Ti, I can't see why your 970 will require assistant from the SATA.

From Tom's Hardware review, this card 970 draw about 133W from the 6+8 pin when gaming (normal real world high demand). Which means each mini 6pin only need to provide 67W if you can balance the load.

Under extreme case (e.g. Furmark), the card can draw 193W from the 6+8pin. so, each mini 6pin need to deliver 97W. But my setup already proved that the mini 6pins can do that without issue. Also, I don't think your general use is Furmark.

I want to have a driving sim, and can buy an Xbox or ps4, a PC, or put in a card and re-install windows 10 (which is not booting on my 5.1 mac which runs twin CPUs. I've got two fast clock rate four thread CPUs to replace my slow clock rate factory CPUs too. Not sure if the twin CPU macs will assist a game work in Win 10 ...

Can I run a PC driving sim like Assetto Corsa on my MacPro with its twin CPUs, and is GTX 970 or a 7950 fast enough compared to buying a PC with for instance a GTX 1050 card?

Dual CPU won't help gaming at all. It's all about CPU speed, not core count.

970 has almost 2x 1050's performance. 1050 is a very low end card. Even the 7950 is tiny bit stronger than 1050 in some benchmarks.

Anyway, if you want anything close to a driving sim. I think PS VR is the easiest way to achieve that. With a mCable, the PS VR graphics can be greatly enhanced.

 

[MagicWok]

Yup, that was kind of my conclusion too. I have read a lot of threads about powering different GPUs and the most safe way to power a card that requires 6-pin + 8-pin without a second PSU, pixal and all that crap is the following:

2 x mini 6-pin to normal 6-pin (from the board) --> A converter from two normal 6-pin to 1 x 8-pin

1 x 15pin SATA Power to 6pin

Correct ? ? ?

You only need a cable like this Dual Mini 6pin > 8pin for the 8pin connector. You can then follow the advice above for the +6pin connector.