Question Powering my graphics card with a second UNCONVENTIONAL psu?

Sep 15, 2019
8
0
10
0
So I have an old Dell Optiplex 780 that I’ve been using for running old games. I got an NVIDIA GTX 1060 to play some newer games, and I’m learning that this card has no business being in this PC. But that only makes it a more interesting challenge!

So I’ve read about and seen videos of folks using a second PC psu to power their graphics card by shorting it through their onboard one, but I’m looking on trying something a little more....unconventional.

Something like this: GALYGG 12V DC Switching Power Supply 150W, Universal Regulated Transformer AC 110V-220V to DC 12V, for LED Strip Lights, Radio, Computer Project https://www.amazon.com/dp/B06XR3WK1Y/ref=cm_sw_r_cp_api_i_V6VFDb4B1RRTX or this: https://www.amazon.com/Waterproof-Transformer-Adapter-Accessories-Warranty/dp/B075RDM4K8/ref=mp_s_a_1_3?keywords=150w+12v+power+supply&qid=1568605945&sprefix=150w+12&sr=8-3

I can easily wire something like these up to correctly provide power to the appropriate sections of a 6-pin connector. My question is, is the 12VDC output of a power supply like either one of these safe for powering a graphics card? Truth be told, I’ve already tried this, but unfortunately it was with a psu that at 100W, only matched the requirements of the 1060......so it lasted about 20 minutes. My main motivation with going with something like the links above is I’m trying to keep the extra wires and cables to minimum. The power supply I used that died on me was actually small enough to fit in the case with everything else.
 

Darkbreeze

Titan
Moderator
The whole thing, is a bad idea. I'd forget about it and get back to something more conventional if it were my hardware. Then again, some of you don't seem to care that much about the potential for damaging their cards or other hardware, so I'm sure my words of discouragement won't mean much to you even though I've seen ten other questions just like yours that ended badly just in the last three months.

Garbage in, garbage out. Use the right hardware for the job and avoid not only the probable death of your graphics card but also the waste of money on a solution that was never more than poor at best.
 
Sep 15, 2019
8
0
10
0
The whole thing, is a bad idea. I'd forget about it and get back to something more conventional if it were my hardware. Then again, some of you don't seem to care that much about the potential for damaging their cards or other hardware, so I'm sure my words of discouragement won't mean much to you even though I've seen ten other questions just like yours that ended badly just in the last three months.

Garbage in, garbage out. Use the right hardware for the job and avoid not only the probable death of your graphics card but also the waste of money on a solution that was never more than poor at best.
Can you direct me to some of these questions? The only reason I posted was because I couldn’t find any instances of somebody who did something like this. If I’d have been able to find a similar post that ended badly, I wouldn’t have had to ask the question.
 
Sep 15, 2019
8
0
10
0
Um, why don't you just try upgrading the machine's normal PSU? I realize Dell PSUs tend to be a bit nonstandard, but one of the first search hits I got seems to point the way:

https://www.dell.com/community/Desktops-General-Read-Only/Optiplex-780-PSU-upgrade/m-p/4421110/highlight/true#M960416

Although the specific product they recommend seems to be discontinued, perhaps you can find similar.

Good luck.
Thank you! That guy's form factor on his MT must be different from my DT case. The ATX/EPS psu form factor is 150mm wide, whereas my power supply is 125mm with maybe 5mm to spare before it's hitting the motherboard. Unfortunate too, because it looks to fit otherwise.
 
Sep 15, 2019
8
0
10
0
So I have an old Dell Optiplex 780 that I’ve been using for running old games. I got an NVIDIA GTX 1060 to play some newer games, and I’m learning that this card has no business being in this PC. But that only makes it a more interesting challenge!

So I’ve read about and seen videos of folks using a second PC psu to power their graphics card by shorting it through their onboard one, but I’m looking on trying something a little more....unconventional.

Something like this: GALYGG 12V DC Switching Power Supply 150W, Universal Regulated Transformer AC 110V-220V to DC 12V, for LED Strip Lights, Radio, Computer Project https://www.amazon.com/dp/B06XR3WK1Y/ref=cm_sw_r_cp_api_i_V6VFDb4B1RRTX or this: https://www.amazon.com/Waterproof-Transformer-Adapter-Accessories-Warranty/dp/B075RDM4K8/ref=mp_s_a_1_3?keywords=150w+12v+power+supply&qid=1568605945&sprefix=150w+12&sr=8-3

I can easily wire something like these up to correctly provide power to the appropriate sections of a 6-pin connector. My question is, is the 12VDC output of a power supply like either one of these safe for powering a graphics card? Truth be told, I’ve already tried this, but unfortunately it was with a psu that at 100W, only matched the requirements of the 1060......so it lasted about 20 minutes. My main motivation with going with something like the links above is I’m trying to keep the extra wires and cables to minimum. The power supply I used that died on me was actually small enough to fit in the case with everything else.
 
...

So I’ve read about and seen videos of folks using a second PC psu to power their graphics card by shorting it through their onboard one, but I’m looking on trying something a little more....unconventional.

....
If your GPU isolates the 12V power on the GPU connectors from the 12V power from the PCIe slot then it could work, theoretically. But if you've tried this already I suspect not.

It's been a while since I've dabbled in this kind of stuff but as I recall the problem is one of load balancing. When you parallel two power sources simplistically the one that can maintain the higher voltage under load will carry the bulk of the load all the way up to it's destruction even while the other is cool and quiet (could that be what happened on your first attempt??).

Here's a description of a circuit that might be helpful:
https://www.edn.com/design/power-management/4419835/Multiple-PSUs-share-load

You might also get by if using identical PSU's that have nearly identical performance characteristics and are finely tuned to nearly identical +12V outputs, but I don't think that's what you're attempting.
 
Reactions: UtopiaNemo
Sep 15, 2019
8
0
10
0
If your GPU isolates the 12V power on the GPU connectors from the 12V power from the PCIe slot then it could work, theoretically. But if you've tried this already I suspect not.

It's been a while since I've dabbled in this kind of stuff but as I recall the problem is one of load balancing. When you parallel two power sources simplistically the one that can maintain the higher voltage under load will carry the bulk of the load all the way up to it's destruction even while the other is cool and quiet (could that be what happened on your first attempt??).

Here's a description of a circuit that might be helpful:
https://www.edn.com/design/power-management/4419835/Multiple-PSUs-share-load

You might also get by if using identical PSU's that have nearly identical performance characteristics and are finely tuned to nearly identical +12V outputs, but I don't think that's what you're attempting.
It may have been what was happening on my other power supply, but I think my main error there was the obvious blunder of using a power supply that was just big enough for my card. As in the wattages matched exactly.

So correct me if I’m mistaken: the issue with power sharing is just that the higher voltage unit ends up carrying most of the load. Is this an issue if the higher voltage is adequate for the job? I’m using an old Dell that has a max output of 255W. If I used a 500W power supply, it would be more than adequate to feed everything. The only issue would be making sure its voltage remained higher than the other......and of course the aforementioned problem of ATX psus not being able to fit in the first place. sigh
 

InvalidError

Titan
Moderator
If your GPU isolates the 12V power on the GPU connectors from the 12V power from the PCIe slot then it could work, theoretically. But if you've tried this already I suspect not.
AFAIK, nearly all GPUs with AUX power connectors power Vcore exclusively off AUX power. On the few GPUs that use some slot power for Vcore, you have only 2-4 phases wired to slot power and the others exclusively to AUX power. I don't remember seeing an in-depth GPU analysis where AUX is commoned with slot power.
 
Reactions: UtopiaNemo
Sep 15, 2019
8
0
10
0
AFAIK, nearly all GPUs with AUX power connectors power Vcore exclusively off AUX power. On the few GPUs that use some slot power for Vcore, you have only 2-4 phases wired to slot power and the others exclusively to AUX power. I don't remember seeing an in-depth GPU analysis where AUX is commoned with slot power.
Short of getting the card schematics, would it seem logical that i could test for this by plugging the card into a pcie slot, energizing it, and using a meter to test the aux pins? Or conversely, plugging in the aux power and testing voltage on the pcie pins?
 

InvalidError

Titan
Moderator
You can test for continuity between AUX 12V pins and slot 12V by measuring resistance or diode voltage between the 12V pins on the edge connector and 12V pins in the AUX connector. Alternatively, you could also plug the board in the motherboard and then probe from 12V pins on the motherboard's ATX power connector and GPU AUX power connector, no need to turn the PC on and risk shorting something out while measuring.
 
Reactions: drea.drechsler

Darkbreeze

Titan
Moderator
I don't remember seeing an in-depth GPU analysis where AUX is commoned with slot power.

Can you clarify what you mean by "commoned", because I was about to go "whaaaat" until it occured to me that you were probably not saying that cards with auxiliary power don't also USE slot power, just that they don't conjoin the power in some way. I'd like to be sure though because at first glance it sure seemed like you were saying that cards using auxiliary power don't also use slot power, and I'm sure that isn't what you were saying.
 
Reactions: UtopiaNemo
Sep 15, 2019
8
0
10
0
You can test for continuity between AUX 12V pins and slot 12V by measuring resistance or diode voltage between the 12V pins on the edge connector and 12V pins in the AUX connector. Alternatively, you could also plug the board in the motherboard and then probe from 12V pins on the motherboard's ATX power connector and GPU AUX power connector, no need to turn the PC on and risk shorting something out while measuring.
Ok, so every third or fourth slot pin had continuity to AUX ground, which is to be expected....but NONE of the AUX +12V pins had continuity to slot pins. Which is what I was hoping. So really I should be fine with any appropriately rated power psu to power just the card.
 

Darkbreeze

Titan
Moderator
Yes, "appropriately rated power" being the key. That definitely doesn't mean some power brick that plugs into the wall.

That card should probably not be auxiliary powered by anything less than a 200w device, preferably some form of actual PC power supply whether ATX, mATX or one of the specialized smaller form factors. Even a Flex ATX unit would be ok if it was rated for the appropriate amount of power. And the main reason I suggest not going with anything less than 200w is twofold.

One, most of these cheaper type supplies (Assuming you're not going to buy something from Seasonic or Delta) are probably not even remotely capable of actually supplying their listed capacity and then sustaining it for any length of time. And two, while that 6 pin suggests a maximum draw of 75w you have to almost always make allowances for the occasional spike outside of spec, because just about all cards at some point are prone to it. Not to mention, it's always a bad idea to run something off a power supply of any kind that is toeing the line on required capacity because it's nearly a guarantee that it's going to run a lot hotter than you want to see if you do that.

So, those are my thoughts on the matter but I'm in agreement with the idea that finding an actual power supply that will fit your (probably) proprietary form factor that simply has a higher capacity. That would be the correct thing to do. Obviously you could also just get a decent aftermarket unit and the appropriate and available ATX to DELL adapters that are out there, but you'd have to run it outside the case since it's doubtful there's any way to make one work IN the case you have now.

There's a reason they make this crap proprietary. It's because they don't WANT people upgrading to non OEM hardware and for the most part, it works. They make it so difficult people simply build a whole new system to avoid the hassle and BS.
 
Sep 15, 2019
8
0
10
0
Yes, "appropriately rated power" being the key. That definitely doesn't mean some power brick that plugs into the wall.

That card should probably not be auxiliary powered by anything less than a 200w device, preferably some form of actual PC power supply whether ATX, mATX or one of the specialized smaller form factors. Even a Flex ATX unit would be ok if it was rated for the appropriate amount of power. And the main reason I suggest not going with anything less than 200w is twofold.

One, most of these cheaper type supplies (Assuming you're not going to buy something from Seasonic or Delta) are probably not even remotely capable of actually supplying their listed capacity and then sustaining it for any length of time. And two, while that 6 pin suggests a maximum draw of 75w you have to almost always make allowances for the occasional spike outside of spec, because just about all cards at some point are prone to it. Not to mention, it's always a bad idea to run something off a power supply of any kind that is toeing the line on required capacity because it's nearly a guarantee that it's going to run a lot hotter than you want to see if you do that.

So, those are my thoughts on the matter but I'm in agreement with the idea that finding an actual power supply that will fit your (probably) proprietary form factor that simply has a higher capacity. That would be the correct thing to do. Obviously you could also just get a decent aftermarket unit and the appropriate and available ATX to DELL adapters that are out there, but you'd have to run it outside the case since it's doubtful there's any way to make one work IN the case you have now.

There's a reason they make this crap proprietary. It's because they don't WANT people upgrading to non OEM hardware and for the most part, it works. They make it so difficult people simply build a whole new system to avoid the hassle and BS.
Thanks for the advice. Yes, I’m planning on buying an EVGA 400W ATX since it’s both well-rated and inexpensive.

I’m also well aware of the reasons manufacturers make proprietary systems, and I’m also aware of how much easier it would be if I just upgraded to something more appropriate.

The whole point for me is that this is a fun project. I’m not a pc gamer with a commensurate ratio of income to slush money. I’m a dad with five kids who likes occasional retro games, who also got a free Dell Optiplex 780. I had an extra $100 I could divert to splurging on an unreturnable refurbished graphics card, which I bought without knowing anything other than it used the same pcie slot I had in my aging PC. Instead of declaring my mistake a total loss and scrounging up another $500-$1,000 or more that it would take just to get something that would work with this card, I’m treating this as a fun experiment to see how I can make these square pegs fit into round holes. It looks like I’ll be able to do that for less than $40. So $140 total for a Frankensteined “gaming rig” that I can learn from, and enjoy with my kids, is pretty damn good. And I’m not the least bit sorry that doesn’t happen to meet your full approval.
 

InvalidError

Titan
Moderator
Not to mention, it's always a bad idea to run something off a power supply of any kind that is toeing the line on required capacity because it's nearly a guarantee that it's going to run a lot hotter than you want to see if you do that.
That is mostly true for lower efficiency designs. Once you get into decently high efficiency, there isn't much heat to get rid of per cubic inch of PSU volume and most of the losses are in the transformer which does not care much about temperature. Fun fact: all things being otherwise equal, a larger transformer will have higher losses for a given amount of output power just from having more material in the magnetic path going through the cycle and run hotter due to having less surface area per volume to get rid of that heat with so you actually do want to be close to the smallest transformer size you can get away with for best efficiency. That's why some high-powered high-efficiency PSUs are using twin transformers instead of a single cheaper and more space-efficient larger one.

The biggest concern I'd have with using a LED PSU for computer stuff is that since 12V LED strips are generally steady loads with relatively wide voltage tolerance due to the use of a drop resistor for every three LEDs for white and blue ones, they may lack the transient response performance that a GPU requires.
 
Reactions: UtopiaNemo

ASK THE COMMUNITY

TRENDING THREADS