GTX 780 and Power Consumption

MentalVizion

macrumors regular
Original poster
Oct 30, 2013
144
3
Austria
Hey,

I currently have a GTX 780 (Asus reference model IIRC) installed. It is chilling in there for almost 2 years now I'd say. Back then, I used two of the HDD bays to safely power the card with two additional SATA to PCIe cables, as the 780 has a TDP of 250W.

Now I am quite in the need of these HDD bays. I searched around again, and appereantly, it seems quite safe to just hook the card up to the logic board with the 6 and 8 pin cables. MacVidCards also DOES NOT list the card under his "These cards pretty much need an external PSU" list. However, he does list the 780 TI. BUT, according to the nVidia site, the 780 TI also has a TDP of 250W. Then again, I've seen people using overclocked EVGA 780 TI models on just the logic board connectors, and not having troubles at all.

TLDR: I suppose it is safe to hook up my GTX 780 (3GB) to just the internal logic board 6 and 8 pin connectors, and not waste 2 HDD slots?

I do have a dual core 4,1 (upgraded to 5,1), in case that matters.
 

joebclash

macrumors regular
Jun 14, 2016
196
114
That's how I hock up my
Hey,

I currently have a GTX 780 (Asus reference model IIRC) installed. It is chilling in there for almost 2 years now I'd say. Back then, I used two of the HDD bays to safely power the card with two additional SATA to PCIe cables, as the 780 has a TDP of 250W.

Now I am quite in the need of these HDD bays. I searched around again, and appereantly, it seems quite safe to just hook the card up to the logic board with the 6 and 8 pin cables. MacVidCards also DOES NOT list the card under his "These cards pretty much need an external PSU" list. However, he does list the 780 TI. BUT, according to the nVidia site, the 780 TI also has a TDP of 250W. Then again, I've seen people using overclocked EVGA 780 TI models on just the logic board connectors, and not having troubles at all.

TLDR: I suppose it is safe to hook up my GTX 780 (3GB) to just the internal logic board 6 and 8 pin connectors, and not waste 2 HDD slots?

I do have a dual core 4,1 (upgraded to 5,1), in case that matters.
Not sure I completely understand your question but I power my gtx from the 6 pin connector on the motherboard and it works great. No problems in years.
 

Draeconis

macrumors 6502a
May 6, 2008
969
264
Hey,

I currently have a GTX 780 (Asus reference model IIRC) installed. It is chilling in there for almost 2 years now I'd say. Back then, I used two of the HDD bays to safely power the card with two additional SATA to PCIe cables, as the 780 has a TDP of 250W.

Now I am quite in the need of these HDD bays. I searched around again, and appereantly, it seems quite safe to just hook the card up to the logic board with the 6 and 8 pin cables. MacVidCards also DOES NOT list the card under his "These cards pretty much need an external PSU" list. However, he does list the 780 TI. BUT, according to the nVidia site, the 780 TI also has a TDP of 250W. Then again, I've seen people using overclocked EVGA 780 TI models on just the logic board connectors, and not having troubles at all.

TLDR: I suppose it is safe to hook up my GTX 780 (3GB) to just the internal logic board 6 and 8 pin connectors, and not waste 2 HDD slots?

I do have a dual core 4,1 (upgraded to 5,1), in case that matters.
So, this kind of question has been done to death around here. A quick search wouldn't have hurt.

The Asus 780 from a cursory google search has 8-pin and 6-pin power connectors, and like all other GPUs, will usually pull up to 75w from the PCIe slot, giving a maximum supported draw of up to 300w. Assuming it's only clocked to draw up to 250w, the design may well pull some or all of the 75w supplied from the 6-pin and some or all of the 150w supplied from the 8-pin; it's hard to say exactly what as this is never set in stone.

Ultimately, if you are happy running the risk that the GPU may attempt to pull more power than the cables connected to it are rated for, that's up to you. Some people here will say they've been doing it for years without issue, some will say the traces to the PSU were burnt out and made for an expensive repair job.

Personally, I'd advise against it. If you're only adding 2.5in disks, consider a PCIe to SATA-III adapter? Bit more expensive than you were planning, but cheaper than a replacement logic board.
 

MentalVizion

macrumors regular
Original poster
Oct 30, 2013
144
3
Austria
This thread may help you to understand more about those mini 6pins true limit.

https://forums.macrumors.com/threads/mac-pro-4-1-and-5-1-pcie-aux-power.2035519/
I read through the whole thread yesterday, but as always, there's no generell consensus.
[doublepost=1488983757][/doublepost]
So, this kind of question has been done to death around here. A quick search wouldn't have hurt.

The Asus 780 from a cursory google search has 8-pin and 6-pin power connectors, and like all other GPUs, will usually pull up to 75w from the PCIe slot, giving a maximum supported draw of up to 300w. Assuming it's only clocked to draw up to 250w, the design may well pull some or all of the 75w supplied from the 6-pin and some or all of the 150w supplied from the 8-pin; it's hard to say exactly what as this is never set in stone.

Ultimately, if you are happy running the risk that the GPU may attempt to pull more power than the cables connected to it are rated for, that's up to you. Some people here will say they've been doing it for years without issue, some will say the traces to the PSU were burnt out and made for an expensive repair job.

Personally, I'd advise against it. If you're only adding 2.5in disks, consider a PCIe to SATA-III adapter? Bit more expensive than you were planning, but cheaper than a replacement logic board.
That's the thing: I have yet to find proof of someone, that actually fried his logic board because of this. I know all the stuff you posted. I pretty much just would like to hear some input from people that have a 780 installed with this method, and whether or not it works in the long run.
 

thornslack

macrumors 6502
Nov 16, 2013
410
164
I have a classified 780 and ran it with 6 to 8 pin cables. General consensus is the Mac will shut down before damage occurs. I did have the occasional hard shut down when I was overclocking but once I settled on a sweet spot it was perfectly stable. I now use a titan x (250w) using a six and 8 pin and it works like a charm.
 

MentalVizion

macrumors regular
Original poster
Oct 30, 2013
144
3
Austria
I have a classified 780 and ran it with 6 to 8 pin cables. General consensus is the Mac will shut down before damage occurs. I did have the occasional hard shut down when I was overclocking but once I settled on a sweet spot it was perfectly stable. I now use a titan x (250w) using a six and 8 pin and it works like a charm.
Thanks! Since I only have the regular 780 and am not planning to OC it, I think I really should be good to go.
 
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