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no.pe

macrumors newbie
Original poster
Jan 21, 2019
7
0
Hello to all!

I have a mac pro 5.1 working beautifully with an nvidia gtx970, driving two monitors without a hitch (one is a 4k 32" and the other is a 27" 1080p, both 60hz). In the last days I decided to add an amd r9 380 I had lying around with the premise that it would drive my monitors, leaving the gtx to handle all the cuda intensive apps - and I have indeed seen great improvements! So far, so good!

The problem is that from the get go, when I plug the second 1080p monitor, the system freezes and in general wants hard reboot to snap out of it. With the 4k screen only via displayport, everything is working flawlessly.

I have tried different monitors, all the connections / cables imaginable (hdmi, displayport, dvi, dvi to vga) but to no avail. It is driving me nuts! It shouldn't be a gpu problem, as I tested it on a PC and every port is working great - in the mac pro the second monitor doesn't want to cooperate which leads me to believe there is something wrong with the OSX drivers? The system is up to date in everything, and is running 10.13.6

Maybe two different gpu manufacturers are not meant to be on the same system? If so, why with only the 4k monitor everything is as smooth as butter? Stress tested and all! Any ideas?


Thank you for any input,
N.
 

startergo

macrumors 601
Sep 20, 2018
4,967
2,253
Are you positive there is enough power supplied to both GPU's? Can you measure the current draw with a clamp meter?
 

no.pe

macrumors newbie
Original poster
Jan 21, 2019
7
0
Are you positive there is enough power supplied to both GPU's? Can you measure the current draw with a clamp meter?

Hey startergo and thanx for the quick reply!

Unfortunately here in the office I don't have a clamp meter - If there wasn't enough power, wouldn't it affect other aspects as well? For the last 5 days, the system is super stable, and everything works without a hitch (even sleep / wake is super fast and no shutdowns / restarts of any kind) and I have been rendering through cinema 4D + octane without any problems albeit with only the 32" 4k monitor.. If I didn't want to use the second monitor, I would probably never even guess there is a problem, and I would be a very happy user! :)

If there was a power shortage of some kind, wouldn't it become unstable while under stress as well?
 

startergo

macrumors 601
Sep 20, 2018
4,967
2,253
Logically yes . I would still check power when possible. Are you tapped straight to the PSU cables?
 

no.pe

macrumors newbie
Original poster
Jan 21, 2019
7
0
Logically yes . I would still check power when possible. Are you tapped straight to the PSU cables?

Yes, via power splitter cables. I also tried (because I thought about the power consumption as well) powering the gtx through the motherboard PSU cables, and the r9 380 through the sata-to-power trick I have seen around in the forum. The result is the same: stable system when connected to one monitor, unstable when connected to anything else other than displayport.. So right now I am using the splitter cables just for the cleanliness of the setup rather than the adaptors.. The PSU in theory should not have any problem with the power as it's ~1000w and the GPUs and the m2 drive are the only things drawing power (I don't even have disks installed, nor CD/DVD drives - everything is on server's side).

Oh, I forgot to say that if I plug both my monitors on the gtx 970 (while keeping the 39 380 in the system) everything works as it should - but it kinda defeats the purpose of releasing the CUDA GPU of any unnecessary trouble.

So yeah, I will try and check with the clamp meter - but until then I am at a complete loss :confused:
 

no.pe

macrumors newbie
Original poster
Jan 21, 2019
7
0
Gotta be power.
Aren’t they both 8-pin cards?

Hey Squuiid! Thank you for your input!

No, the r9 380 has 2x6pins, and the gtx 970 has 1x6pin and 1x8pin.. Even so, if it was power, why when I connect both the displays in the gtx 970 (while still have both cards installed) both displays work fine? Again, stress tested and all (c4D, octane, after effects, LuxMark openCL tests), without any hiccup..!
 

no.pe

macrumors newbie
Original poster
Jan 21, 2019
7
0
How are they in Windows? Have you ever tried them in Windows?

Unfortunately, I don't have any installation of windows to check it out (haven't used windows since late 90's).. Do you have any specific test in mind I should check out?

Other than that, I am starting to think that it is driver / kext related with the r9. In system information, it only says "AMD Radeon HD Tonga PRO prototype", and in about this mac it identifies it as AMD R9 xxx 4GB. Inside the professional programs though, the GPU is identified correctly. Have no idea though if it is supposed to be like that..
 

Squuiid

macrumors 68000
Oct 31, 2006
1,867
1,688
Honestly, I think the best person to answer your query would be @h9826790.
He's quite the expert when it comes to cMP power/video card compatibility issues/quirks.
 

h9826790

macrumors P6
Apr 3, 2014
16,620
8,554
Hong Kong
Honestly, I think the best person to answer your query would be @h9826790.
He's quite the expert when it comes to cMP power/video card compatibility issues/quirks.

I suspect that’s simply driver compatibility issue.

Few years back, it’s quite OK to co-install Nvidia and AMD card on the same Mac.

But AFAIK, it’s not like that anymore. The chance of having errors when different GPUs are installed at the same time is much higher now.

For OP, the test is simple. Remove all other GPU but only install the 380. If no problem, then it’s multiple GPU causing issue. If still have problem, then most likely the 380 driver itself is bad for this particular setup.

Unfortunately, I don't have any installation of windows to check it out (haven't used windows since late 90's).. Do you have any specific test in mind I should check out?

Other than that, I am starting to think that it is driver / kext related with the r9. In system information, it only says "AMD Radeon HD Tonga PRO prototype", and in about this mac it identifies it as AMD R9 xxx 4GB. Inside the professional programs though, the GPU is identified correctly. Have no idea though if it is supposed to be like that..

Even you have Windows, that won’t help anything. You should never install both AMD and Nvidia GPU together in Windows. The drivers can’t quite co-exist in Windows.

Also, those R9 XXX etc is normal for this card. This is not a hint that has driver / kext issue.
 
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no.pe

macrumors newbie
Original poster
Jan 21, 2019
7
0
I suspect that’s simply driver compatibility issue.

Few years back, it’s quite OK to co-install Nvidia and AMD card on the same Mac.

But AFAIK, it’s not like that anymore. The chance of having errors when different GPUs are installed at the same time is much higher now.

For OP, the test is simple. Remove all other GPU but only install the 380. If no problem, then it’s multiple GPU causing issue. If still have problem, then most likely the 380 driver itself is bad for this particular setup.



Even you have Windows, that won’t help anything. You should never install both AMD and Nvidia GPU together in Windows. The drivers can’t quite co-exist in Windows.

Also, those R9 XXX etc is normal for this card. This is not a hint that has driver / kext issue.

Hey h9826790! Thank you for your invaluable input!

I just tried what you said, and installed only the r9 380 in the system; alas, to no avail.. The problem with the two monitors still exists, so it must be the driver. Any ideas where to go from here? Should I try any mods as the hackintosh community does with kext injections etc, or is it a dead end / not even worth it?
 

h9826790

macrumors P6
Apr 3, 2014
16,620
8,554
Hong Kong
Hey h9826790! Thank you for your invaluable input!

I just tried what you said, and installed only the r9 380 in the system; alas, to no avail.. The problem with the two monitors still exists, so it must be the driver. Any ideas where to go from here? Should I try any mods as the hackintosh community does with kext injections etc, or is it a dead end / not even worth it?

If your monitor has DP 1.1 / DP 1.2 selection, try different setting. This setting (on the monitor side) occasionally can fix some strange behaviour in macOS.

I am 100% sure R9 380 can drive two monitors at the same time in macOS. I tried that before (back in around 10.13.4). But only 2x 1080P monitor. Not 4k. So, that may make the difference.

Of course 10.13.6 may make the difference as well, but the chance is very very low.

If your 380 can't even drive two 1080P 60Hz monitors. Then something is wrong. Possible hardware failure.

If I were you, the next I will try is a clean OS installation and with R9 380 only. This can rule out almost everything and only down to OS driver issue, or hardware issue (faulty card).
 
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