My Auxiliary Power Supply for my GPU's failed. Here's my fix.

[Dr. Stealth]

My decision for this mod was based on my personal usage. Granted it's not necessary for everyone. I do daily rendering of CGI. My renderer uses hybrid rendering using both CPU's and GPS's simultaneously. When rendering my (2) CPU's and (2) GPU's go to 100% utilization and stay there for many hours.

My (2) x5690's draw up to 260W

My (2) 1080 TI's draw up to 560W

That adds up to 820W. Now, I still need to power 6 SSD's, 96GB of RAM, a GT-120, a spinner HD, the mainboard, backplane, 6 fans and external USB devices.

I was getting too close to the power available from the Macs 980W PSU for me to be comfortable drawing all the power from there using the Pixlas Mod.

It was a simple mod that only required taping 2 wires. Pixlas mod requires taping 8 wires. (That's easier and safer?)

No soldering is required for this mod. If you don't have a soldering iron or are not comfortable with soldering you could also use the same quick-taps used for the pixlas mod or even better use simple wire-nuts.

I chose to solder because it's cleaner and more reliable than mechanical wire fasteners.

My (2) PSU's now have lots of overhead available and are nowhere near their limits. This makes me sleep better at night while my CPU's and GPU's are at 100% usage doing renders.

I wanted to use the fastest GPU's (highest power draw) I could buy and not make that buying decision based on how much power I could pull from my cMP's 8 year old PSU using the pixlas mod.

If I decide to add another 1080 TI I could easily do so with no worries. Faster and more powerful GPU's are always rolling out and if I want to upgrade my cards in the future to something even more powerful I can easily do so.

Anyway like I said, the above is based on my personal needs and usage. One size never fits all.

And this is why I don't do electrical tutorials here on MR. If I did, I guarantee you I will get a post like this.

"OMG ! I did EXACTLY what Dr. Stealth said to do (I think) but when I plugged in my Mac there was a BIG BLUE FLASH and my room filled up with smoke! "

And a silly analogy to go along with it...

You have a property with a single water well. You now realize you need lots more water so you add three or four more output pipes to your one well. (The Pixlas Mod). You are still pulling all your water from the one same well. If you really need more water you need to dig another well.

 

[crjackson2134]

My decision for this mod was based on my personal usage. Granted it's not necessary for everyone. One size never fits all.

No explanation needed although I totally agree with your reasoning here. I would do exactly the same if I had the need.

 

[Cuzzupino]

My decision for this mod was based on my personal usage. Granted it's not necessary for everyone. I do daily rendering of CGI. My renderer uses hybrid rendering using both CPU's and GPS's simultaneously. When rendering my (2) CPU's and (2) GPU's go to 100% utilization and stay there for many hours.

My (2) x5690's draw up to 260W

My (2) 1080 TI's draw up to 560W

That adds up to 820W. Now, I still need to power 6 SSD's, a GT-120, a spinner HD, the mainboard, backplane and 6 fans.

I was getting too close to the power available from the Macs 980W PSU for me to be comfortable drawing all the power from there using the Pixlas Mod.

It was a simple mod that only required taping 2 wires. Pixlas mod requires taping 8 wires. (That's easier and safer?)

No soldering is required for this mod. If you don't have a soldering iron or are not comfortable with soldering you could also use the same quick-taps used for the pixlas mod or even better use simple wire-nuts.

I chose to solder because it's cleaner and more reliable than mechanical wire fasteners.

My (2) PSU's now have lots of overhead available and are nowhere near their limits. This makes me sleep better at night while my CPU's and GPU's are at 100% usage doing renders.

I wanted to use the fastest GPU's (highest power draw) I could buy and not make that buying decision based on how much power I could pull from my cMP's 8 year old PSU using the pixlas mod.

If I decide to add another 1080 TI I could easily do so with no worries. More powerful GPU's are always rolling out and if I want to upgrade my cards in the future to something even more powerful I can easily do so.

Anyway like I said, the above is based on my personal needs and usage. One size never fits all.

I see the pixla mod and seems to me simple to do that. Very nice mod.

So if I can use the same quick-taps used for the pixla on Dr. Stealth mod... then I think I can do that.

Simply I need to undestand where are the two cable for Dr. Stealth mod... that seems to me that are 120v and ground? And another question I have the EU version... so 240V... it is the same cable?

Thanks for the infos.

 

[h9826790]

My decision for this mod was based on my personal usage. Granted it's not necessary for everyone. I do daily rendering of CGI. My renderer uses hybrid rendering using both CPU's and GPS's simultaneously. When rendering my (2) CPU's and (2) GPU's go to 100% utilization and stay there for many hours.

My (2) x5690's draw up to 260W

My (2) 1080 TI's draw up to 560W

That adds up to 820W. Now, I still need to power 6 SSD's, 96GB of RAM, a GT-120, a spinner HD, the mainboard, backplane and 6 fans.

I was getting too close to the power available from the Macs 980W PSU for me to be comfortable drawing all the power from there using the Pixlas Mod.

It was a simple mod that only required taping 2 wires. Pixlas mod requires taping 8 wires. (That's easier and safer?)

No soldering is required for this mod. If you don't have a soldering iron or are not comfortable with soldering you could also use the same quick-taps used for the pixlas mod or even better use simple wire-nuts.

I chose to solder because it's cleaner and more reliable than mechanical wire fasteners.

My (2) PSU's now have lots of overhead available and are nowhere near their limits. This makes me sleep better at night while my CPU's and GPU's are at 100% usage doing renders.

I wanted to use the fastest GPU's (highest power draw) I could buy and not make that buying decision based on how much power I could pull from my cMP's 8 year old PSU using the pixlas mod.

If I decide to add another 1080 TI I could easily do so with no worries. Faster and more powerful GPU's are always rolling out and if I want to upgrade my cards in the future to something even more powerful I can easily do so.

Anyway like I said, the above is based on my personal needs and usage. One size never fits all.

IMO, Pixlas mod still easier and safer.

Pixlas mod actually doesn't require 8 wires tapping. Minimum 4 is enough. Even though still more than 2. But I believe that still easier and safer.

I don't think 2 wires tapping is all you need for an extra PSU setup.

1) The extra PSU need to connect to the wall socket. If the extra PSU is connected to cMP's PSU to draw power but not from the wall. That used at least 2 wires already. And it still need something to jump it.

If that 2 wires are just use to jump the extra PSU. So that, when the cMP power on, the extra PSU will also power on automatically. Then an extra cable management is required to connect the extra PSU to the wall socket.

In any case, that's a bit more than "just 2 wires tapping".

2) If that 2 wires are for high voltage ac power (extra PSU get ac power from the cMP's PSU). IMO, the risk is higher than just tapping few low voltage dc power lines.

3) The extra PSU will affect the cMP PSU's cooling (block some airflow + releasing warmer air to the downstream cMP PSU).


Anyway, easier / safer / etc are very personal in this kind of mod (because both mod are not that hard actually). That's just my own opinion, no right or wrong.

If I were you, I will also go for this super tidy extra PSU for. As you pointed out, your usage is way too close (if not over yet) to that 980W limit under extreme case. An extra PSU is actually "required". Especially we consider the cMP's PSU age, and it may not able to deliver full 980W under any ambient condition. It's better to be safe than sorry.

But also as you said, one size won't fit all. IMO, this mod is way overkill for any single GPU user. There is nothing wrong to do that, but I don't think it's a good option to have an extra PSU inside the cMP if it's not required at all at the very beginning.

 

[Dr. Stealth]

IMO, Pixlas mod still easier and safer.

Pixlas mod actually doesn't require 8 wires tapping. Minimum 4 is enough. Even though still more than 2. But I believe that still easier and safer.

I don't think 2 wires tapping is all you need for an extra PSU setup.

1) The extra PSU need to connect to the wall socket.

Disagree... It only needs to be attached to the Mac PSUs 120V input. 2 wires.

2) If that 2 wires are for high voltage ac power (extra PSU get ac power from the cMP's PSU). IMO, the risk is higher than just tapping few low voltage dc power lines.

Disagree... It doesn't matter if the voltage is 120v or 12v. If you connect wrong, you have a dead mac in either case.

3) The extra PSU will affect the cMP PSU's cooling (block some airflow + releasing warmer air to the downstream cMP PSU).

Disagree... There is actually more room for air flow than having 2 optical drives and associated cabling in the bay. The Aux PSU has it's own large fan which is sucking fresh air from the front and blowing in the same direction as the mac PSU. Much better air flow than blocking the mac PSU with 2 optical drives.

Anyway, easier / safer / etc are very personal in this kind of mod (because both mod are not that hard actually). That's just my own opinion, no right or wrong.

I agree with this ^ ....

If I were you, I will also go for this super tidy extra PSU for. As you pointed out, your usage is way too close (if not over yet) to that 980W limit under extreme case. An extra PSU is actually "required". Especially we consider the cMP's PSU age, and it may not able to deliver full 980W under any ambient condition. It's better to be safe than sorry.

I agree with this ^ ....

But also as you said, one size won't fit all. IMO, this mod is way overkill for any single GPU user. There is nothing wrong to do that, but I don't think it's a good option to have an extra PSU inside the cMP if it's not required at all at the very beginning.

I also agree with this ^ ....

The only other thing I had to do was jump two connectors on the Aux PSU so it would power on without being connected to a mainboard and switch. Piece of cake.

h9826790... You are still my MR friend but we don't agree on all points. And that's Okay.

 

[h9826790]

I also agree with this ^ ....

The only other thing I had to do was jump two connectors on the Aux PSU so it would power on without being connected to a mainboard and switch. Piece of cake.

I agree that this extra PSU is smaller than two optical drive, and better for airflow if compare to two optical drives installed. However, standard cMP won't have two optical drive inside the optical cage.

On the other hand, because there are more room for the air free to flow around the PSU. The fan inside the PSU should not able to help to create any extra differential pressure (inside / outside the cMP). In this case, I think the fan in the extra PSU can mainly suck air already inside the optical cage into the PSU, but not sucking extra air from outside. I really doubt if it can help the cMP's PSU cooling. Especially it can general heat by itself.

 

[Dr. Stealth]

I agree that this extra PSU is smaller than two optical drive, and better for airflow if compare to two optical drives installed. However, standard cMP won't have two optical drive inside the optical cage.

On the other hand, because there are more room for the air free to flow around the PSU. The fan inside the PSU should not able to help to create any extra differential pressure (inside / outside the cMP). In this case, I think the fan in the extra PSU can mainly suck air already inside the optical cage into the PSU, but not sucking extra air from outside. I really doubt if it can help the cMP's PSU cooling. Especially it can general heat by itself.

I purchased my cMP Build-To-Order with two optical drives. Many others have also. They were designed for it.

The fact that I have been running this machine every day for over 6 months under extreme conditions (rendering) speaks for itself. This is not speculation, this is reality. You can hypothesize and speculate about airflow until the cows come home while I'm busy rendering away.

 

[h9826790]

The fact that I have been running this machine every day for over 6 months under extreme conditions (rendering) speaks for itself. This is not speculation, this is reality. You can hypothesize and speculate until the cows come home while I'm busy rendering away.

Please don't get me wrong. Sure it's a working setup. And work well. I have absolutely no doubt on that.

I was just thinking about how can that "provide better cooling" possible by the extra PSU's fan. That's a purely academic discussion. I love to find out the truth and the "why" behind. That's it

The idea in my mind is because much lower stress for the original PSU's component. Therefore, they run cooler, even though the incoming air (at the cMP's PSU point of view) is warmer than before. But the overall temperature still lowered.

So, the cMP's PSU is actually run cooler than before. And the extra PSU fan actually help the air flow inside the optical cage (but not sucking extra fresh air in). Everything has no contraction, and fit both the theory and the real world outcome.

 

[Cuzzupino]

However the external psu solution is not elegant at all but seems to me better in terms of modularity and a mod that not permanet modify the original hardware too... And with ths solution U can however move the second psu internal finding a way to get out the second ac plug to wall. I think I will go this if needed.

Only a question:

Can I use this http://www.add2psu.com/wp-content/uploads/2011/05/adaptor.png ?

 

[Dr. Stealth]

Please don't get me wrong. Sure it's a working setup. And work well. I have absolutely no doubt on that.

I was just thinking about how can that "provide better cooling" possible by the extra PSU's fan. That's a purely academic discussion. I love to find out the truth and the "why" behind. That's it

The idea in my mind is because much lower stress for the original PSU's component. Therefore, they run cooler, even though the incoming air (at the cMP's PSU point of view) is warmer than before. But the overall temperature still lowered.

So, the cMP's PSU is actually run cooler than before. And the extra PSU fan actually help the air flow inside the optical cage (but not sucking extra fresh air in). Everything has no contraction, and fit both the theory and the real world outcome.

Yes, as we discussed before it would be really nice to see a computer simulation of the cMP airflow...

 

[Dr. Stealth]

A mod that not permanetly modify the original hardware too.

Nothing permanent. Just pull out the optical drive carrier and install the PSU. I can reinstall the carrier if I ever need/want to.

 

[Cuzzupino]

Nothing permanent. Just pull out the optical drive carrier and install the PSU. I can reinstall the carrier if I ever need/want to.

I intend if U must open psu and soldering two ac cable togheter to get one ac input cable... if You keep them and jump the atx connector then external or internal do not mod original hardware.

 

[soundrats]

Hi out there, I actually had the idea to use an aux psu in our mac pro 5.1 workhorse in our sound studio. Since we have a new gpu we are running out of power for the gpu which results in black screens sometimes. I was absolutely unsure if it works just with a 2nd psu for the new gpu. I was asking myself: the original psu powers the mainboard, the pice slots and other devices - will it work if I use the 2nd psu for the GPU while the mainboard and so the pcie slots (and so the slot with this gpu) are powered by the original psu.
I guess it works, you did it...are there any problems or do I have to do anything more then connecting the aux psu to the gpu (despite the AC connection of both psu)
Thnx and cheers Tom

 

[kazkus]

Can I use this http://www.add2psu.com/wp-content/uploads/2011/05/adaptor.png ?

Yes.
Actually, I put Corsair RM850x in my MacPro5,1 this weekend, and used ADD2PSU to sync it with the original PSU.
Currently, it is for just one GTX 1080 Ti, but I may put another GPU later.

 

[donluca]

@Dr. Stealth how's the temps on your Mac PSU when it's on full load?

I have thoroughly cleaned my PSU, removed everything in front of it (included the plastic thing for the optical drives which obstructs air) and on full load I still get 70° (and sometimes more).

I'd be scared of using it at anything higher and with another PSU right in front of it...

 

[Grumply]

This is fascinating, and super-clean mod! Bravo.

Am I understanding correctly that with this mod, you don't need to plug the 2nd auxiliary PSU into the wall?

It will draw its power THROUGH the Mac PSU? (so you're just plugging the standard power cable into the back of the machine, and that will supply the power for both PSUs?).

Also, you're connecting the two 120v AC inputs? Input to input?

 

[kmgolden]

Yes, he's saying you don't need to plug the 2nd aux into the wall. If you do this, you'll be jumping the input cables on both PSUs. Another way to think about it: this basically means you're connecting both PSUs to the plug in the back of the machine, so that the power from the wall is pulled directly into both PSUs, not really through the mac PSU, if that makes sense. In that sense, yes you'd be connecting input to input.

Also, instead of soldering both PSUs, you could just strip the power cable for the aux psu and solder those ends to the mac pro psu input, if you have warranty concerns

 

[ivanengler]

what exactly happens if your computer sleeps? will the GPUs be completely shut down / disconnected from all power? or do they retain memory contents in the GPU RAM and therefore will still require some amount of power? if so, is your additional PSU still running during sleep? or is sleep not possible at all with this method? THANK YOU.