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Sorry for the delay -- waiting for a response from my friend. I had him set the Dell P2718Q to 4K (3840x2160) and move the mouse and drag some windows around. No discernible lag and certainly no ghosting. In the Graphics/Displays system report the monitor shows 3840 x 2160 @30Hz. He doesn't use it at this resolution -- everything is too small.

I have a 2014 15-MBP with integrated graphics, and driving my Dell 2715Q is borderline unusable. Wishing an such as CS6 or Camtasia or Powerpoint, it works OK. But dragging things around, it ghosts and lags.
 
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So exploring all gpu options, I have a power supply question for the experts.

If a gpu has 1x 6pin + 1x 8pin it seems (theoretically) like it would be safe to do:

-2x 6pin (75w per = 150w total) to 1 x8pin (max 150w draw)
-2x SATA (55w per = 110w total) to 1 x6pin (max 75w draw)

However with the SATA connections since its using a splitter, I'm wondering if the draw will necessarily be equal or close to equal? Is it possible that the 6pin in the gpu could at some point pull the max 75w from only one SATA? Or are splitters wired in such a way that it is balanced between both connections?

I guess the same applies for the 6pin to 8pin since there is a splitter but I think I read this is ok?

Also if the above is correct, given that this is for rendering (hours straight sometimes) is this in general a bad idea? I can't find the posts but I believe people have stated that while the max for a 6pin is 75w, sometimes it will go above this threshold?

I'm really trying to avoid doing the pixlas mod which is why I'm wondering about this since its just adding cablesI appreciate any comments.
 
So exploring all gpu options, I have a power supply question for the experts.

If a gpu has 1x 6pin + 1x 8pin it seems (theoretically) like it would be safe to do:

-2x 6pin (75w per = 150w total) to 1 x8pin (max 150w draw)
-2x SATA (55w per = 110w total) to 1 x6pin (max 75w draw)

However with the SATA connections since its using a splitter, I'm wondering if the draw will necessarily be equal or close to equal? Is it possible that the 6pin in the gpu could at some point pull the max 75w from only one SATA? Or are splitters wired in such a way that it is balanced between both connections?

Also if the above is correct, given that this is for rendering (hours straight sometimes) is this in general a bad idea? I can't find the posts but I believe people have stated that while the max for a 6pin is 75w, sometimes it will go above this threshold?

I'm really trying to avoid doing the pixlas mod which is why I'm wondering about this since its just adding cablesI appreciate any comments.


For your info, this is how I only use the two mini 6pins to power 2x HD7950

https://forums.macrumors.com/thread...mac-with-2-d700s.1732849/page-5#post-21722712

https://forums.macrumors.com/thread...or-approaching-silence.1982499/#post-23120938

And this is how I use only the two mini 6pins to power a 6+8pin 1080Ti

https://forums.macrumors.com/threads/getting-my-5-1-ready-for-vive-vr.2046670/page-3#post-25429070

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

The results shows that the mini 6pins can deliver up to around 120W before shutdown protection kicks in.

I am not recommending you to go this route. But just let you know how capable of the mini 6pins are. I “over stress” them for almost 3 years now. Still no issue so far.

GPU draw more than 75W from 6pin for a short period of time is normal. That 75W limit is more on average power draw. The momentary power draw can be much higher than that. AFAIK, it’s absolutely normal.

I never use the SATA power to drive a GPU. But your plan should work without any issue. No matter the 2x mini 6pin or the 2x SATA cable, should balance the load up to a very reasonable level.

Anyway, may I know which card you are targeting now? May be someone using the same card and can share his experience with you.
 
Thanks for the links, lots to read. I was looking at a 1080ti and there was one other that I can't remember. I might have someone willing to do the Pixla mod for me so maybe I don't have to deal with the SATAs.

If that works out, one thing I haven't quit found is a firm number on how much power is left over from the PSU if I have dual x5690s, 64gb RAM, 2HDD+2SSD? If I want to use multiple cards I'm not sure what realistically can be powered for intensive long running tasks like rendering.
 
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