Combining 2 PSU in Parallel to 1 mobo

G

GreatestOne

Limp Gawd
Joined
May 15, 2005
Messages
488
Surprisingly I cant find much info on this, or a how to... obviously you cant just plug in 2 PSU and make them both work for one mobo, and I did read from one site about an adapter kind of thing that makes them "communicate" with each other. It seems tons of people are doing it (for obvious reasons these days) but I cant find out one way to actually do it...
 
I did see one video on how you can pretty much strip a small bit on the green and gray wire (going into the MB) on the primary PSU and then solder or wrap the same from the second PSU to it and that should work, but just afraid of not getting warranty covered if I start doing stuff like that.

I think the Add2Psu is a decent item, although $22 seems quite a bit for such a thing but I guess it will save me some time and any problems with warranties....

The reason is I got a 750W I've had for a while, sitting here, and a 400W... the 750W is no enough to cover my rig, and the 400 obviously is not enough even in addition to cover all. I actually need another 600-700W, which I see a Thermaltake on sale for $30 after rebate, so I rather spend $52 than $200+ for a 1300W+ PSU.

Any other suggestions are welcome if I am missing something.
 
GreatestOne said:
The reason is I got a 750W I've had for a while, sitting here, and a 400W... the 750W is no enough to cover my rig, and the 400 obviously is not enough even in addition to cover all. I actually need another 600-700W, which I see a Thermaltake on sale for $30 after rebate, so I rather spend $52 than $200+ for a 1300W+ PSU.

Any other suggestions are welcome if I am missing something.
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Assuming that your sig is up-to-date, your current 750W is more than enough to cover that PC. Unless you added like three extra video cards or 40+ hard drives to that PC, your power related issues may just be the PSU being defective.
 
Dangman said:
Assuming that your sig is up-to-date, your current 750W is more than enough to cover that PC. Unless you added like three extra video cards or 40+ hard drives to that PC, your power related issues may just be the PSU being defective.
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Sorry, ya ignore my sig... I'll be having 1150W worth of just video cards plus 45W for CPU and I have no idea how much my Gigabyte mobo needs.
 
GreatestOne said:
Sorry, ya ignore my sig... I'll be having 1150W worth of just video cards plus 45W for CPU and I have no idea how much my Gigabyte mobo needs.
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What are the specs of this PC? Lemme guess, you're mining?

Oh and only go for Thermaltake's Toughpower PSUs if you have to buy Thermaltake. The rest of their PSUs lines aren't that good.
 
MouseTrap said:
What video cards and how many will you be adding?
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Dangman said:
What are the specs of this PC? Lemme guess, you're mining?
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Will have

GA-990FXA-UD3
Sempron 145
1x4GB Gskill Ripjaw
3x7950
3xR9-270

Pretty sure I dont have to answer your latter query.... :D

[/QUOTE]Oh and only go for Thermaltake's Toughpower PSUs if you have to buy Thermaltake. The rest of their PSUs lines aren't that good.[/QUOTE]

Thanks, searching now................

cwaffles said:
Using this myself with 2 950w power supplies, works great.
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Which one, the Add2PSU? Just ordered one, not worth my time to muck around, I'm sure it'll be fine for $22.

I just ordered the Rosewill CAPSTONE-750... seems like the cheapest $100 gold there is with pretty good ratings at Amazon and egg.

With these I guess I'l put the three 7950 on the old 750W and the MB, CPU, and three 270's in this one.

I'll cancel this one if someone can suggest a better one atm.
 
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I've used the variable delay version of the add2psu small board and it works quite well. It is pricy for what it is, but it makes for a clean connection.
 
Which one, the Add2PSU? Just ordered one, not worth my time to muck around, I'm sure it'll be fine for $22.

I just ordered the Rosewill CAPSTONE-750... seems like the cheapest $100 gold there is with pretty good ratings at Amazon and egg.

With these I guess I'l put the three 7950 on the old 750W and the MB, CPU, and three 270's in this one.

I'll cancel this one if someone can suggest a better one atm.
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Using the simple 24pin atx connection splitter with 2 Corsair TX950 psus
 
I just stick a paper clip in the green wire and any black wire. Been working fine mining 24/7
 
GreatestOne said:
Surprisingly I cant find much info on this, or a how to... obviously you cant just plug in 2 PSU and make them both work for one mobo, and I did read from one site about an adapter kind of thing that makes them "communicate" with each other.
Click to expand...
It's safe to do, so long as you keep each rail separated, i.e., you don't want the +12V from the 24-pin connector of one PSU to connect to the 24-pin connector of another PSU or they'll fight one another. Normally a PSU will adjust its own outputs, so if it thinks the +12 is too high, it will cut back on it, but if the rail is too low, it will raise it. But if a second PSU's +12V is connected to it, the first PSU loses some control over the +12V rail -- imagine a car with two independent set of controls and two drivers who don't know what the other is doing and who want to drive *slightly* differently.

So use one PSU for one motherboard and maybe one video card, and connect the other PSU to other video cards. Connect the green wires of the PSUs together.
 
hajalie24 said:
I just stick a paper clip in the green wire and any black wire. Been working fine mining 24/7
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I didnt wanna mess with the internal wirings too much in case I had to return the new PSU, so even though the paperclip and joining the wires seemed pretty easy, I wanted to go "legit" so we'll see how the Add2PSU thing works, should be here any day now......


larrymoencurly said:
It's safe to do, so long as you keep each rail separated, i.e., you don't want the +12V from the 24-pin connector of one PSU to connect to the 24-pin connector of another PSU or they'll fight one another. Normally a PSU will adjust its own outputs, so if it thinks the +12 is too high, it will cut back on it, but if the rail is too low, it will raise it. But if a second PSU's +12V is connected to it, the first PSU loses some control over the +12V rail -- imagine a car with two independent set of controls and two drivers who don't know what the other is doing and who want to drive *slightly* differently.

So use one PSU for one motherboard and maybe one video card, and connect the other PSU to other video cards. Connect the green wires of the PSUs together.
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This was my "plan":

Bronze 750W PSU
Gig Mobo, Sempron 145, USB flash drive (Linux) = ~150W?
3x (R9 270) = ~400W-450W

Platinum 750W PSU
3x (HD 7950) = ~ 550-600W
 
hajalie24 said:
I just stick a paper clip in the green wire and any black wire. Been working fine mining 24/7
Click to expand...

Just curious on when to short the second PSU if it is not connected to the primary PSU?

Should I short it before I boot up primary?
Or short it quickly after I boot up?

I don't think precise parallel boot and short is very feasible?
 
pkkevin said:
Just curious on when to short the second PSU if it is not connected to the primary PSU?

Should I short it before I boot up primary?
Or short it quickly after I boot up?

I don't think precise parallel boot and short is very feasible?
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Actually this is what I'm doing and it actually works perfectly, unless u want just one button to turn the system on and off.

They say to make sure to turn the secondary power on first, then the primary connected to the mobo. This is what I been doing and no problems yet... I think that order is pretty important.
 
Short it before you turn on your PC. Nothing happens, even if the PC hasn't been turned on for a while. I don't know much about PSUs, but I'm assuming that the motherboard tells the graphics card when its on and then the GPU tries to draw power.

You also don't need to spend $22 on an Add2PSU adapter, you can always get an adapter off ebay for like $10, shipped from the USA.

http://www.ebay.com/sch/i.html?_odk...cto&_nkw=dual+power+supply+connector&_sacat=0
 
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hajalie24 said:
Short it before you turn on your PC. Nothing happens, even if the PC hasn't been turned on for a while. I don't know much about PSUs, but I'm assuming that the motherboard tells the graphics card when its on and then the GPU tries to draw power.

You also don't need to spend $22 on an Add2PSU adapter, you can always get an adapter off ebay for like $10, shipped from the USA.

http://www.ebay.com/sch/i.html?_odk...cto&_nkw=dual+power+supply+connector&_sacat=0
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Ya true that, just didnt wanna mess around with that for a few bucks since I will have been leaving this on 24/7 etc... but dont matter, shorting the green and black is the best thing since black beans.
 
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Thanks for the info.

In short, it works. I have shorted/turned on the secondary PSU and than turn on the primary PSU and everything works flawlessly.

Now to share some details of my experiment.

The secondary PSU (PSU2) is connected only to a 7950 video card.

I tried to short PSU2 the green and black slot with a wire. The PSU fan immediately turns on. I have a Kill-a-watt and see ~1-3W draw from the outlet.

Once I turn on the power of my computer, I see around 20-30w.

When I try running cgminer, PSU2 now have around 160w

I also measured my computer (PSU1), idle is around 50w and with cgminer I see around 120w

in total, 280w and 230w for the 7950.


hajalie24 said:
Short it before you turn on your PC. Nothing happens, even if the PC hasn't been turned on for a while. I don't know much about PSUs, but I'm assuming that the motherboard tells the graphics card when its on and then the GPU tries to draw power.

You also don't need to spend $22 on an Add2PSU adapter, you can always get an adapter off ebay for like $10, shipped from the USA.

http://www.ebay.com/sch/i.html?_odk...cto&_nkw=dual+power+supply+connector&_sacat=0
Click to expand...
 
As an eBay Associate, HardForum may earn from qualifying purchases.
pkkevin said:
The secondary PSU (PSU2) is connected only to a 7950 video card.

I tried to short PSU2 the green and black slot with a wire. The PSU fan immediately turns on. I have a Kill-a-watt and see ~1-3W draw from the outlet.

Once I turn on the power of my computer, I see around 20-30w.

When I try running cgminer, PSU2 now have around 160w

I also measured my computer (PSU1), idle is around 50w and with cgminer I see around 120w

in total, 280w and 230w for the 7950.
Click to expand...

My numbers, some dont make sense at all: (all cards under 99% load)

MB only 175W
270 (1) 125W (I thought this was 150W in specs?)
Sapphire 7950 220W (I thought this was 200W in specs?)
(Brand New)

MB + 270 (1) 520W (??????? math?)

MB 600W (again... where is the extra 200W coming from?)
+ Sapphire 7950
(Brand New)
 
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