Mac Pro 3.41 and GTX 980TI power cable best connection without external supply

[Cassio_Frasson]

Hi,

looking at my scenario, MacPro 4.1 system with firmware updated to 5,1 and upgraded 2xCPU X5690 3.41Ghz , 12 GB RAM, 240 GB SSD/MSATA Kingston PCI, USB 3.0 PCI, and only two hard disk days connected. Now with a GT-120 GPU just to consider overall power.

So for now only have 2 x sata connectors, from the free hard disks bays, available to power the GTX 980 TI.

My main idea, is to buy the most simple & powerless GTX 980 TI reference card from ZOTAC or EVGA and PC model, since where I live (Brazil) its quite impossible due the costs+taxes(60%!) to buy from www.macvidcards.com ... unfortunately!!

Even don't want to buy the overclocked models, and also not considering to overclock the reference card itself, specially to avoid more power needed and risks associated with Mac Pro power supply limitations and without using any external supply.

My question is related with the most missing part about the GTX 980 TI with MacPro 4.1/5.1 and not using external power supply.

What is the best way to plug the 6 and 8 PIN cables?

There are many posts everywhere, affirming that there is no need to have a external power supply or by the other side from other posts advising for sure you need a external power supply if you don't want to damage the motherboard.

So the GTX 980 TI reference card is compatible or not without any external power supply?

Considering if 6 PIN expect 75 Watts and 8 PIN expect 150 Watts in the GPU plugs.

And since MacPro has 2 x 6 PIN in motherboard, each can drive 75 Watts, so this could be enough to power to 8 PIN in GPU?

If only remaining 2 x Sata plugs available, will this be enough to feed the power in the 6 PIN plug in GPU?

Or should be considered to used all 4 x Sata to feed one single 6 PIN plug in GPU to minimize risks from the motherboard being damaged?

How MacVidCard guys recommend the GTX 980 TI connection without external power supply?

Any other risks related with if not using MacVideo firmware custom cards modifications?

Thanks!

 

[Ursadorable]

So for now only have 2 x sata connectors, from the free hard disks bays, available to power the GTX 980 TI.

Doesn't the 4,1 have the two extra 6 pin power sockets on the motherboard like the 3,1 exclusively for powering a video card?

 

[h9826790]

OP want to know how to power the card and everything stay within the rated limit.

Dual 6 pin means it's not good enough for a 6 + 8 config.

From other's experience, a simple 6->8 pin cable can do the tricks. However, if OP is not comfortable for that, Yes, dual 6 pin (75W x2) to 8 pin (150W) is a safer way to do it.

AFAIK, the SATA port are rated up to 55W. So, dual SATA (55W x2) should be good enough to feed the remaining 6 pin (75W) safely.

 

[spyguy10709]

The 2 extra pins on the 8 pin connector do not actually carry any extra power, they carry extra GROUND pins. Early 6 pin capable power supplies were built to the standard of being able to carry only 75 watts on the GPU connector. As power requirements grew, in order to certify that they could carry 150 watts, they used a new connector that was electrically compatible.

The mac pro has more than enough power, and is certainly built with cables able to withstand the extra power.

You'd be fine using a 6 pin to 8 pin adapter for the 8 pin connector, and just connecting the 6 pin. Don't bother with sata adapters.

 

[h9826790]

The extra GND pin (Sense B) will allow the card to pull 150W from a 6pin (75W) source. And there is no guarantee that's safe. In fact, the Mac Pro will shut itself down when pulling about 120W from a single 6pin source (a protection mechanism). It's simply impossible to pull full 150W from a single 6pin source on the cMP. The PSU is strong enough, but the trace on the mobo is not. I think we better let OP know this fact rather than tell him it's 100% safe to do so. It's his choice to use the 6->8 pin or not, but his decision should not be based on our false information.

 

[Draeconis]

If you don't want to get another PSU, don't get a 980 Ti. As stated in numerous other threads, the most power the 4,1 or 5,1 design Mac Pro ca provide is 225w; 75w from the PCIe slot, and 75w from each 6-pin power cable.

Best card therefore to fit within the power envelope is the stock 980 with 2x 6-pin power connections. If you want something that will draw more than 225w (and do so from one or more 8-pin connections) do yourself a favour and get an additional power supply.

Your machines wasn't cheap. It's amazing how many people are willing to risk destroying their machines because they can afford to drop over £500 on a new GPU, but can't be bothered to spend comparatively nothing on a proper PSU to power it...

 

[h9826790]

Or you can go through the Pixlas mod. Which gives your Mac a "proper way" to power the 8 pin. The mod itself is relatively low risk. All you need is just some proper tool, and attach the 8pin to the correct line.

https://forums.macrumors.com/threads/pixlas-4-1-mac-pro-mod.1859652/

 

[Cassio_Frasson]

And what you guys think about the GTX 980 TI HYBRID model?

Since this card really push hard from the power supply, even if connected directly as show in this other discussion
https://forums.macrumors.com/threads/pixlas-4-1-mac-pro-mod.1859652/

Do you think when directly connected to the power supply with GTX 980 TI HYBRID could be used from the stock OC or even pushing further from the overclocked possibilities in Mac Pro 4.1/5.1 with two X5690 3.41 CPU?

Thanks

 

[ifraaank]

What is the final word on this? Should I use extra power from the Sata connectors, or what is the very best and safest way to fully power a 980 Ti on the internal power supply? (Since @MacVidCards website says it's possible)
Thanks

 

[h9826790]

I guess the non OC version is ok to powered by the mini 6pins. But the OC version should be powered directly from the PSU (Pixlas mod, if not consider extra PSU). Since the PSU is rated 980W, I can't see any issue on powering the OC 980Ti.

I have dual 7950 in my cMP at this moment with internal power only. I don't think a single 980Ti can draw more than 2x 7950. It's the war of power consumption between a real GPU and 2 space heater, the GPU can't win

 

[ActionableMango]

What is the final word on this?

I am not an expert, but I have been following MP video card upgrade threads fairly closely for several years, so I'll try my best.

The 980 works great in a MP. The Titan X works great in a MP.

The 980Ti on the other hand, is hit and miss. Some get it to work with no supplementary power, others cannot. Speculation is that Nvidia "bins" the chips and the good ones go to the Titan X, and the worse ones go to the 980Ti.

MVC's 980Ti has both firmware and hardware modifications to make it work in a MP with no supplemental power.

Many cards with one 6-pin and one 8-pin work fine because the second 8-pin connector is really cosmetic or there for marketing purposes. The best analogy I've heard is from MVC, who equates this with 8-tip exhaust headers on a 4 cylinder car. The extra tips don't do anything other than sell cars. I personally have experienced this with a 6+8 GTX 680. Despite having an 8-pin connector, it did not draw anywhere near 225W, nor did any one power tap exceed 75W. I didn't even use a 6-to-8 pin adapter, I just connected two 6-pin cables. Many people experience this with many types of cards.

But other cards with one 6-pin and one 8-pin really do need the adapter and the extra power, like the 980Tis. Simply hooking up 2x6-pin won't work.

I have seen people do the following for cards that require supplemental power (where simply using two 6-pin supply cables like I do doesn't work):

1. Adapter - Use a 6-to-8 pin adapter and hope for the best. Cheapest method and works for many.
2. Direct P/S Wiring - Wire new 8-pin supply wires directly to the power supply (Pixlas mod). This is, in my opinion, the best although hardest solution. But it provides power directly from the power supply, which has plenty of wattage, and will work for future power hungry cards.
3. Second P/S - Add a supplementary internal power supply designed to fit in an optical drive slot. Requires running AC power into the case and up into the optical bay, which is not easy, and tapping the on/off sense to a free SATA power connector.
4. Spread the load - Combine the two 6-pin sources together into an 8-pin, then y-cable them back off to the 6 and 8 pin connectors on the video card. (So instead of one 75W rated source going to a 75W potential load (100%), and one 75W source going to a 150W load (200%), you have 150W rated source going to a 225W potential load (150%). The idea here is that 50% over the rating of two connectors is far more likely to be within the actual limits than 100% over the rating of a single connector.
5. Tap into SATA - Combine the two 6-pin sources together for the 8-pin connector (75W+75W=150W). Combine two SATA connectors together for the 6-pin (55W+55W exceeds the 75W needed).

For what it's worth, I've never, ever, heard of people here on MR causing damage when using methods 1, 2, 4, and 5*. And this even includes people that have hooked up dual 7950 or dual GTX970 cards, running two 6-pin sources to four 6-pin connectors via y-cables with no additional power supply. Whenever I have seen people exceed the power envelope, the computer has shut off.

So while people have theorized about the traces in the motherboard frying, what reportedly happens is that the current limiter in the power supply shuts off power before the traces in the motherboard blow. I've read that Intel designed the Mac Pro motherboards, and it's reasonable to assume they or Apple did a good job of it.

In the past I used to be one of those that would warn doom and gloom about exceeding the rated power, but I've been forced to change my mind as a result of the reported evidence over the last couple of years that shows otherwise. While I wouldn't promise safety, the reports so far are positive. And if anyone has actually blown their motherboard traces, I've never seen nor heard of it.

* Note I didn't include #3. I have seen a couple of people report damage due to using method #3, but in both cases they were using two video cards and crossed the power from each supply (motherboard and third party supply), with one cable from each supply going to each card. As opposed to using the motherboard to power one card and the third party supply to power the other card, which MVC recommends. So ironically, the one method described as "safe" earlier in this thread (adding a supplementary supply) is the only method I've ever heard of that causes damage.

Of course, "what I've heard" is anecdotal, but it's the best I can share.

 

[ifraaank]

@ActionableMango I think tapping into SATA might be the safest bet for me then. I don't need the optical drives. Thanks for this very nice answer.

 

[Machines]

"How (you) guys recommend the GTX 980 TI connection without external power supply?"

It is possible to install a GTX 980 Ti in a cMP without the need of an external power supply .

You must have a video card with just a single 8 pin (150 W) and a single 6 pin (75 W) power booster connector .

I have done this installation for a client and there are no reported issues , so this is not a theoretical design .

Here are the parts you need :

A ) 2 x 18 AWG male 6 pin mini PCIe to male 6 pin standard PCIe power booster adapter cable (Heavy duty Mac Pro video card power cables) .





B ) 1 x dual female 6 pin standard PCIe to single male 8 pin standard PCIe power booster splitter cable (EVGA part number W000-00-000143 ) . This cable should be included in some high end EVGA graphics card products .





C ) 2 x OWC Newer Technology AdaptaDrive 3.5" to 2.5" form factor adapter .





D ) 2 x Mac Pro factory HDD bay sled (should already be in your Mac) .



E ) 1 x Dual SATA power to 6 pin standard PCIe power splitter adapter cable (StarTech part number SATPCIEXADAP ) .





F ) 2 x female SATA power to male SATA power extension cable .



G ) 1 small bottle of rubberized Superglue (Gorilla Super Glue) .




Instructions :

Install both the Web and CUDA drivers before you install the video card in your Mac Pro .

Install your GTX 980 Ti video card .

Attach both parts A into part B . Then connect both parts A into the two Mac Pro's mini 6 pin PCIe power connectors . Attach part B into the video card's 8 pin PCIe power connector .

Attach each part C onto each part D .

Attach each part F onto each part C . Remove the short black plastic part (key) on part F's male connector first .



Superglue each area where a part F connects to a part C . Superglue requires exposure to air to cure . Use small amount of glue on both sides of each connection . Less is more with superglue . Superglue , by the way , is electrically non-conductive . Let dry .

Attach both parts F to part E .

Install both part Ds into the Mac's HDD bays.

Attach part E to the video card's 6 pin PCIe power connector .

Your GTX 980 Ti is now able to receive all the power it requires internally to operate at load in a cMP , as follows :

PCIe host computer interface slot provides 75 W (normal ) .
8 pin PCIe power cable to the video card provides 150 W (normal ) .
6 pin PCIe power cable to the video card provides 66 W (slightly below normal ) . Should be 75 W normal .

Total wattage provided to the video card is now 291 W .

It is normal for this card (EVGA GTX 980 Ti SC+ model number 06G-P4-4995) in a cMP to use no more than 241 W at load , so we are providing more than enough juice .

The most important thing you must remember is no connection must ever come loose when your Mac is on (or being Started Up) , so snap lock all the connections in place . It might also be a good idea to glue all the SATA extension cable connections .

 

[prvt.donut]

Has anyone actually measured the power going through each power supply cable for a GTX980ti to see how much it actually is drawing from the psu?

Be good to get some actual facts as apposed to all this conjecture.

----Update----

Ok, so on page 2 of Nvidia's manual for the GTX980ti it states the following:


Minimum System Requirements

• System Power Supply
  Minimum 600 W or greater system power supply with two 6-pin PCI Express supplementary power connectors
  
  

 

[Machines]

Has anyone actually measured the power going through each power supply cable for a GTX980ti to see how much it actually is drawing from the psu?

Be good to get some actual facts as apposed to all this conjecture.

----Update----

Ok, so on page 2 of Nvidia's manual for the GTX980ti it states the following:


Minimum System Requirements

• System Power Supply
  Minimum 600 W or greater system power supply with two 6-pin PCI Express supplementary power connectors

What conjecture ? This is an actual installation , power connections measured , stressed tested and in the hands of a rendering client . Did you carefully read my post ?

 

[prvt.donut]

What conjecture ? This is an actual installation , power connections measured , stressed tested and in the hands of a rendering client . Did you carefully read my post ?

Yes I did, but it doesn't say you measured the power actually flowing through each cable using a multimeter. It looks like you added up the potential power output of the connections you tapped.

Again, Nvidia's own manual says only two 6pin PCIE power connectors are required under the minimum system requirements on page 2.

#didyoucarefullyreadmypost

 

[Machines]

Yes I did, but it doesn't say you measured the power actually flowing through each cable using a multimeter. It looks like you added up the potential power output of the connections you tapped.

It's in my build notes from a project completed around three months ago , so I am going from memory . I used a program called Hardware Monitor from Bresink and a Kill-A-Watt device . I do remember the total wattage consumed at load , which I listed , that each SATA HDD backplane provided 33 W (66 W total) and that the PCIe slot provided near its rating (75 W) . Simple arithmetic tells us what the two load-balanced motherboard connectors jointly provided - the remainder of the maximum consumed at load (around 100 W), although I did record the actual . The card I used is rated for 250 W max and at load I never consumed more than 241 W actual in a Nehalem Mac Pro .

 

[prvt.donut]

It's in my build notes from a project completed around three months ago , so I am going from memory . I used a program called Hardware Monitor from Bresink and a Kill-A-Watt device . I do remember the total wattage consumed at load , which I listed , that each SATA HDD backplane provided 33 W (66 W total) and that the PCIe slot provided near its rating (75 W) . Simple arithmetic tells us what the two load-balanced motherboard connectors jointly provided - the remainder of the maximum consumed at load (around 100 W), although I did record the actual . The card I used is rated for 250 W max and at load I never consumed more than 241 W actual in a Nehalem Mac Pro .

Thanks Machines. That is great work. I found some pretty in depth reviews but they just totaled up the measured power consumption of their multimeters and charted them together not actually showing the individual power draw from each PCIE aux connector.

What I find interesting is that Nvidia's manual states two 6 pin supplies are the minimum requirement implying that there is no need to go trying to tap into other sources for extra power.

Maybe because whilst the official maximum rating for each 6 pin is 75watts, the standard probably includes around 10% overhead

(this is merely conjuncture you honor! Sustained! But your honor, this is standard practice in the electronics industry ! Over-Ruled! Phew)

and as such Nvidia knew that powering 240-250 watts from the PCIE slot (rated 75) and two aux 6 pins each at 75 gives 225watts 10% above is 247.5 watts.

Maybe they made a last minute decision to add an 8 pin connector as "gamers" see that and think, "hmmm, yes, this is a powerful card, whilst leaving in the information that the minimum requirements are two 6 pin connectors as they are capable of handling the load that the card will be pulling from them.

It is well known that the Apple PCIE 6 pin aux connectors will auto shutoff if over 120w is drawn to protect the circuitry. It is not a leap to assume that most 6pin connectors are similar or have the same fail safes?

It certainly would explain why they say that in the manual.

Even if the design of the GTX 980ti placed a strict 75watt limit on the PCIE slot and 6 pin socket, the 8pin socket would be only ever asked to draw at full maximum load 100 watts, which is well about 20% below the 120w fail safe point.

But I digress, I will need to read more into the specifications of the 6 pin standard and/or manufacturers implementations of it.

 

[ifraaank]

I have dual 7950 in my cMP at this moment with internal power only.

How did you set this up? Are both cards connected to the two mini-6-pin? Or did you use sata or pixlas mod?

 

[h9826790]

How did you set this up? Are both cards connected to the two mini-6-pin? Or did you use sata or pixlas mod?

I just get the power form the 2x mini 6pin.

My original setup is like this, each card connect to a min 6 pin port by a mini 6pin - > 2x 6pin cable. The max power draw will occasionally over the official 75W limit when editing 4K video, but the setup is 100% stable.

But now, I re-arrange the cables, so each mini 6pin connect to one of the 6pin on the card. The reason is sometime I will gaming in Windows, and not all games works well with crossfire. So, if I share the load, I can disable crossfire and OC one of the card to give me better gaming performance without seriously overloading any of the mini 6 pin source.

 

[Machines]

How did you set this up? Are both cards connected to the two mini-6-pin? Or did you use sata or pixlas mod?

I've done this two different ways - both involving grabbing power from the SATA backplane connectors .

Sometimes one high end GPU gets booster power from one motherboard mini 6 pin connector > video card standard 6 pin connector AND from one HDD SATA backplane connector > video card standard 6 pin connector via an adapter cable .

Sometimes , one high end GPU gets booster power from one motherboard mini 6 pin connector > video card standard 6 pin connector AND from TWO HDD SATA backplane connectors > video card standard 6 pin connector via an adapter and splitter cable .

The key is to measure all the power sensors at load carefully with the greatest number of connections first and then reduce them if possible . This requires knowing how much the GPU actually draws at load and how highly the power connections are rated . The approach above might not work with video card 8 pin connectors .
[doublepost=1457726665][/doublepost]

I just get the power form the 2x mini 6pin.

My original setup is like this, each card connect to a min 6 pin port by a mini 6pin - > 2x 6pin cable. The max power draw will occasionally over the official 75W limit when editing 4K video, but the setup is 100% stable.

But now, I re-arrange the cables, so each mini 6pin connect to one of the 6pin on the card. The reason is sometime I will gaming in Windows, and not all games works well with crossfire. So, if I share the load, I can disable crossfire and OC one of the card to give me better gaming performance without seriously overloading any of the mini 6 pin source.

It has been my experience that a single AMD 7950 at load consumes around 183 W of power from all three connectors (on the video card) in a Nehalem Mac Pro . But I always worry about pulling too much juice from any single source .

 

[ifraaank]

Thanks guys. Just to be sure - I can use the two SATA power connectors that goes to the optical drive bay, right? (for the additional power to gpu) I need four HDD's but not any optical drives.

 

[Machines]

Thanks guys. Just to be sure - I can use the two SATA power connectors that goes to the optical drive bay, right? (for the additional power to gpu) I need four HDD's but not any optical drives.

Back in the day the TransIntl DX4 system grabbed power from the Mac Pro motherboard's optical drive bay power header and split it four different ways to feed four individual drives . Since the power header expected a draw from two ODD , it provided up to approximately (5V x 2A + 12V x 2.5A factory Superdrive requirement) per drive for 2 x 40 W = 80 W total max . Some users have used this header to feed GPU power booster needs , but I prefer to grab the 33 W per HDD backplane connectors .

If you are really serious, then you must learn how to tap directly from the Mac's factory installed PSU cables .

 

[prvt.donut]

If you are really serious, then you must learn how to tap directly from the Mac's factory installed PSU cables .

100% Agree, the PSU in the Mac Pro is very good and can easily power multiple GPUs so connecting directly to the cables coming off it and adding six or 8 pin plugs is the safest and cleanest method. Putting another PSU in the case is unnecessary. although doing such a power connection mod is scarier. I am sure there would be a market for people selling pre-modded PSUs (if soldered beautifully, not just clipped)

 

[Machines]

100% Agree, the PSU in the Mac Pro is very good and can easily power multiple GPUs so connecting directly to the cables coming off it and adding six or 8 pin plugs is the safest and cleanest method. Putting another PSU in the case is unnecessary. although doing such a power connection mod is scarier. I am sure there would be a market for people selling pre-modded PSUs (if soldered beautifully, not just clipped)

The maximum I have ever drawn from a cMP PSU with internally mounted components at load was only 730 W (out of 980 W rated max) and I have built some very high end configurations . These beasts are also incredibly efficient . I've detected only around 50 W of waste energy from them .