I think the safety mechanism that shuts down the PSU at high power loads is there to prevent any damage to the logic board traces. I'm not certain about this but I guess it should trigger above 300W which is the global power limit of the PCIe slots and power outlets. I've never had any problem so far running an overclocked Titan X at constant 110% TDP.
The only drawback is that the PCI and PSU fan speeds are linked to power consumption and get very noisy at 275W. This incited me to do the internal PSU mod anyway (solder an 8 pin PCIe cable directly into the PSU to the GPU) which resulted into much more acceptable fan speeds without any worrying impact on temperatures (PSU/PCI 925/1550rpm vs 1500/2250rpm at 275W).
Install an Nvidia GeForce GTX 980 TI in Your Mac Pro 1,1 or 2,1 Mark Sokolovsky - 2018.03.02 Despite the Mac Pro 1,1 and 2,1 (2006/7) models hitting past the 10-year mark, there is, surprisingly, a great amount of hardware that is still available for use.
Nvidia Gtx 980 Ti 6gb Mac
I was worried the PSU couldn't handle the Titan X as it has the same TDP than the 780Ti which is notorious for being able to shut down the PSU. I just don't get the exact reason why one would work and not the other.
This might be related to the GPU peak consumption and/or slight discrepancy between power safety threshold on different Mac Pros. As netkas said, the 980ti is a more risky choice as some samples have turned out to be more power hungry, however I've been surprised to see what my MP could handle. I'm also surprised to see that some samples are able to exceed the TDP as it seems that Maxwell cards tend to throttle to strictly enforce the TDP limit. Those who want to give it a go should be prepared to do one of the internal/external PSU mods or to resell the card just in case. I think the safety mechanism that shuts down the PSU at high power loads is there to prevent any damage to the logic board traces.
I'm not certain about this but I guess it should trigger above 300W which is the global power limit of the PCIe slots and power outlets. I've never had any problem so far running an overclocked Titan X at constant 110% TDP. The only drawback is that the PCI and PSU fan speeds are linked to power consumption and get very noisy at 275W. This incited me to do the internal PSU mod anyway (solder an 8 pin PCIe cable directly into the PSU to the GPU) which resulted into much more acceptable fan speeds without any worrying impact on temperatures (PSU/PCI 925/1550rpm vs 1500/2250rpm at 275W). I was worried the PSU couldn't handle the Titan X as it has the same TDP than the 780Ti which is notorious for being able to shut down the PSU. I just don't get the exact reason why one would work and not the other.
This might be related to the GPU peak consumption and/or slight discrepancy between power safety threshold on different Mac Pros. As netkas said, the 980ti is a more risky choice as some samples have turned out to be more power hungry, however I've been surprised to see what my MP could handle. I'm also surprised to see that some samples are able to exceed the TDP as it seems that Maxwell cards tend to throttle to strictly enforce the TDP limit. Those who want to give it a go should be prepared to do one of the internal/external PSU mods or to resell the card just in case.
Well I found enough information in these two threads to get me started: I also translated the essential information and reported my experience on a french forum here: There is no precise tutorial. The mod requires a bit of disassembling and soldering skills, don't do it if you can't solder properly or are afraid to disassemble a PSU (or alternatively try the solderless mod from the second link). If you feel confident enough with the required knowledge and skills then these links should be enough.
If not you should find someone to help you do it (electrician, electronics technician, DIY hobbyist). The mod is for 4.1/5.1 Mac Pros. There's nothing too complicated there, you have to spot the +12V and GND terminals into the PSU, solder the 8 wires of a PCIe cable to them and route the cable to the GPU. Each one of those who completed the mod took his own approach to it. I used two PCIe 8 pin 45cm extender cables, one hooked to the GPU, cut one end of the other to solder it on the PSU and connected the two together.
I just got a GTX 980 Ti and I have to say I am having some trouble. I installed it, boots off the web driver, but it is far from smooth. Mouse is jittery, floaty and sometimes like pushing mud. GPU programs like creative cloud eventually bog down.
It's very hard to use in the yosemite interface. Put the GTX 680 back in and it's all normal. Can't figure it out. 980 reports excellent render times in Blender and Cuda-z, but it doesn't seem to be working to it's full potential on the Mac UI.
Nvidia Gtx 980 Ti Specs
Thought it was maybe drivers, but then saw that others were using it just fine. It reports in system profiler as 'nvidia graphic device' and in photoshop shows up as experimental nvidia.not sure what I should do. I would really like to use this card.
Could it be it's not getting enough power?
Nvidia Geforce Gtx 980 Ti Update
An item that has been restored to working order by the eBay seller or a third party not approved by the manufacturer. This means the item has been inspected, cleaned and repaired to full working order and is in excellent condition. This item may or may not be in its original packaging. See the seller’s listing for full details. Seller notes: “ Like New condition with Back-plate installed and Fully tested with Mac pro dual processes. ” Connectors: DisplayPort Output, HDMI Standard Output, Dual-link DVI, DVI Output Chipset/GPU Model: NVIDIA GeForce GTX 980 Ti Brand: EVGA ACX Model Cooling Component(s) Included: Fan with Heatsink APIs: CUDA, DirectCompute, DirectDraw, OpenCL, OpenGL 4.2 MPN: Does Not Apply Compatible Port/Slot: PCI Express 3.0 x16 Chipset/GPU Manufacturer: NVIDIA Memory Type: GDDR5 SDRAM Memory Size: 6GB UPC: Does not apply.