Hi guys. As an electronics newb, I was wondering if any of you could give some thoughts on the potential pitfalls of using two PSUs to power a single rig? Using the basic theory that the green wire is "power on" and connecting/shorting this to a ground (black) wire turns on the PSU, I could see in principle that it should be easy enough to wire two PSUs together, by connecting/soldering PSU#2's green wire and one earth to the corresponding cables on PSU#1. The fact that you can buy these ready made adapters seems to confirm my thoughts. My case setup easily has room for two smaller, seperate PSUs but not a single, larger (750W+ for example) unit. I have a 620W corsair and a 520W corsair backup unit that I'd like to incorporate into the rig. The idea being that the 520W corsair would power the watercooling pumps, hard disks, DVD drive etc (potentially secondary GPU) whilst leaving the main unit to power the CPU, MOBO and primary GPU. However, IIRC, I've read somewhere before that using exclusively the 12v rails on a PSU with no load whatsoever on the 3.3v or 5v rails can cause considerable damage to the unit. Is this correct? If so what can be done to help "balance" the load on a secondary PSU? What uses the 3.3v and 5v lines? Could I connect some sort of resistors or such to the 3.3v & 5v rails to effectively put load on them? Or is the whole thing too much arseache? Thanks in advance
2 PSU's? Dude, trust me, you do not need one. The day your computer won't power-up, we will talk. Until then, you can easily power up your computer with a 520W GPU. You are wasting your time and money. Moreover you encourage companies to produce those useless 1k and above PSU's, as they know they target you in the thought that Watts are everything, were it is not. It is the amperage. Let's look at the comparison with CPU's Does a P4 3.0Ghz, surpasses in performance an Intel Core 2 Duo 2.6Ghz? Of course not. Does a AMD Athlon 6000+ surpasses in performance an Intel Core 2 Duo 2.6Ghz? Of course not. CPU's like PSU's , MHz or GHz don't say anything well little on the CPU.
if you want this... IF you want this the thread where i asked my Q's about shorting PSU's may be a nice place to start: http://forums.bit-tech.net/showthread.php?t=148353 It might be a solution, and it would be interesting to see this work i guess. Not that it makes much sense to have 2 PSU's in a single rig, but who cares? It's not like SLI or CrossFire or Skulltrail or phase change cooling or CCFL lights or that Scythe Orochi heatsink or building a case in a washing machine toy or that Asus Trinity 3850 X3 or guilding your mousebuttons or 30" screens or building a torture rack to silence the HDDs makes any sense either.
Hi guys, Thanks for the responses but I think you might have both missed something in that rather long babble of a post I wrote: What is also worth considering is that whilst I've seen that a HX 620W can run a dualie and two GTXs in SLi; I'm not confident that it'll cope so well with a heavily overclocked quad core, power hungry SLi board, two volt modded GTXs, DVD drive, 2 hard drives, 9x120mm case fans on a rheobus, two Laing DDCs, case lighting... (I could go on but I think I've probably made my point by now ). It leaves me with two options if I wanna be able to go SLi in the future, as well as catering for storage expansion (more hard disks): 1. Get rid of the Corsair 620W and get something else (this will obviously cost me a few quid) 2. Use the other Corsair 520W that I already have to do the job. Now, whilst option #1 seems more sensible option, #2 will actually cost me nothing and the case I own already caters for 2 PSUs, so finding it a place to live is as simple as screwing in four screws. I definitely need at least one otherwise it won't turn on
You didn't say anything about turning it on in your first post... how the hell we we supposed to know? And you really should cheack out the thread i linked, all your questions about loading the rails have been answered pretty well there by local hero mvagusta
Thanks for that Xtrafresh . Did you ever get round to giving it a go? It's not something I've tried and tbh, I've shorted PSUs for testing pumps, fans, lighting etc plenty of times on an older PSU (using only the 12v rail) and it still runs fine. Wouldn't want to take the same gamble with a decent Corsair jobbie though.
no, i haven't come around to it. I've been vapourmodding (read: not doing anything) for the past 45 days. This weekend was the first time in ages i've gotten some work done, and 10 minutes ago i posted the first update from that. Clicky in my sig to see what's up I will try to short one of the old AOpen PSU's i have lying around pretty soon though to try out different lighting schemes i have in mind.
I didn't really pick up on this earlier as I just had a quick flick through the replies: So.. Like I stated previously I do need one. Most people find that much essential. A 520W Corsair probably would power the rig in my sig but if you'd taken the time to actually read my post you'd have noticed the mention of the potential for adding another 8800GTX. A 520W Corsair would simply not suffice in that situation. The wasting of time and money is an individual opinion and when referring to computer parts on a computer enthusiast site, your opinion (whilst being as valid as anyone elses) seems irrelevant. This is the bit I find most interesting. "I" encourage companies to produce 1K PSUs??? Really? How's that? By not buying one? I own a 620W Corsair (which appears to be the very same PSU you yourself are using) along with a "backup" 520W Corsair. My reason for purchasing them was not as you have incorrectly assumed: "Wow 620W!! That's hella watts, must purchase!!!111!!!. but was instead, an informed decision, based on their triple 12V rails rated at 50amps and 40amps max (respectively) and their very stable voltage regulation. They are proven performers. Believe it or not, I didn't buy them because they looked pretty or because I liked the big numbers on the box. Erm.. good comparision . Did my post count get reset to one? GoodBytes: I'm not sure if it's your mission to offend, or whether you are just trolling in an effort to get a reaction but I think you need to be a little more careful in constructing your replies and comments. This isn't the first time I've seen you insulting other members for simply asking a question that you don't like. Don't make assumptions about others knowledge. You could have said what you felt you had to say in a much more constructive and positive manner. [/RANT] A bit of further research suggests that putting a secondary GPU on a seperate PSU is probably not a good idea. Still, I could probably just about get away with the Q6600, 2 x 8800GTX and mobo on the 620W and leave everything else to the other one. Though I'm beginning to think that the whole idea might just be too much arseache
Here's a good Wattage calculator that has options set in for OCing and such. http://www.silentmods.com/modding/PSU_Watts_Calculator.html I think GoodBytes had good intentions, a little miscommunication is all. Good luck if you decide to pursue this!
Miss communication indeed. @WhiskeyAlpha RANT, I will be more careful of what I say. It would seam that it is hard to project a tone of what I say, on the way I say something. I will apply more thought on how I structure my sentences. Thank you. Note that English is not my first language, and i still barely know English grammar. If you compare my posts from 3 years ago, (you might need to look for other forums) [sample idea of my old posts: no or totally wrong punctuation which sometimes changed the complete meaning of sentences, uncountable spelling mistakes, sentences that make absolute no sense, looping on my points for paragraphs, and you see a lot of: "And", "so", "due to the fact that" all over a simple post]. you can see that my English increased dramatically. I do put effort and learning it and improve it. Now, about my PSU: The reason why I have the 620W Corsair PSU, is because the place where I got it, sold it for the same price as he 520W. So I was like: "ok, why not". Moreover I got this PSU, as I wanted a quiet PC (without costing a fortune with watercolling (at the time), and all with a nice look to it, without any "flash" to it) . And at the time it was/seam the best solution.
I wasn't aware that english wasn't your first language Goodbytes, I suppose that's a compliment really. It just felt like you were calling me an idiot for even thinking of this and that I was the fall-guy for your obvious frustrations concerning over-the-top 1000W+ PSUs. The simple fact is, I already have the two units so it wouldn't cost me anything, as well as having ample room for the two of them in my case. Therefore "wasting my time" was irrelevant, as all it would involve me doing is putting 4 screws to hold the thing in - hardly time consuming for your average bit-tech geek . I think you maybe needed to read the post thoroughly before replying in such a patronising and frankly, offensive tone. Many of the points you made are simply irrelevant to the original questions I asked. I'm sure you'd feel the same way if you had posted a request for some help/advice and I'd insulted you instead of giving you anything useful. Whilst you're in the process of picking up English, we have an age old saying: "If you can't say something nice, say nothing at all". Good luck
Okay, now a rule of thumb (that I just made up but it makes sense) You can use as many PSUs as you want, but make sure your voltages don't get crossed. Or if something is receiving power from one PSU keep the other away from it. For the GPUs they get some of their power from the mobo and the rest from the connectors. The two PSUs may not have the same value for 12V so they shouldn't be mixed. However for HDDs, pumps, fans, lights DVD drives etc, are fine to be powered from the second PSU.
I noticed something funny, and it seems no-one picked up on it, or no-one has bothered to pick up on it anyway. Watts = amps x volts, so in a way, wattage is very closely related to amperage. For example, a psu that can deliver 50w total at 12v will be able to deliver half the amperage that a 100w 12v psu could. Another funny thing is that apparently i'm a local hero Nah, i'm a pretty small contributor compared to some other guys around here, but thanks anyway xtrafresh I would reccomend getting a single big psu, and either mod your current case to fit it, or just get a case that will fit the big psu. But, if i were in your shoes, i'd use both psus aswell It's always better to have more power than you need, an extra 200w is a great thing. It means smoother more reliable power, cooler running psu, longer life, better efficiency so you can actually use less power from the power point, plus the more watts your psu is, or the more psu's you have, the larger your e-penis I'd suggest using the 620 for the mobo & one gtx, and use the 520 for everything else, just as you said Both psu's will have all the rails loaded well, as long as you have some something using the 3.3v of the 520w - Now in the other thread i recommended a 3.3ohm 10 watt resistor for the 3.3v rail, as this would balance the small load of some fans and/or lights on a presumably weak generic psu - this won't be good for you tho, it will still be unbalanced! But you will need to balance the loads of a med/large powerfull psu, so you would want to draw at least a few amps on that 3.3v rail! I'd reccomend say 3 x 10w 3.3 ohm resistors in parrallel, which will give you 1.1 ohms resistance = 3 amps draw, which would be good i think. Now, each resistor is still only using 3.3w of power, and being rated at 10w, they should produce next to no heat, but all three next to each other = 3 x tiny heat, which may mean a bit of warmth - a bit of warmth isn't a problem by the way, they should still last for years and years like this! I'd suggest keeping them at least 5mm apart to avoid this heat build up, you could even attach them to the metal of your case with a bit of heat transfer adhesive, or clamp them down or cable tie, whatever & use heat transfer paste to ensure they stay nice & cold! even if the case is painted, no probs, it's still way too good of a heatsink Don't forget to make sure the cable you use is happy with 3a, or if you use 3 cables, 1a each.
Thanks for the input guys. There seems to be some conflict of opinion here though and it's what I've encountered reading elsewhere. A common thing that is mentioned is to ensure that each device is getting it's power delivery from only one PSU. Therefore, if I were to put one of the GPUs on the 520W unit (as mvagusta suggests), could I not be encountering issues due to the fact that the 620W will be providing power to the mobo (and hence the GPUs 75W, PCI-E power)? Or does the fact that the mobo is actually regulating the current being delivered to the PCI-E slots alter this somehow? Oh and thanks for the tips on "loading" the 3.3V rail. What about the 5V though?
The hdd's will be using some 5v and the graphics card will also be using some 5v, so all is good. If you have any fans or lights on the 5v that's fine aswell, either way is ok. There is a little bit of resistance from the connector of one gpu, to the other gpu, to the 12v inputs on the mobo - this resistance is minimal, but the 12v will flow down the path of the least resistance, which will be from the power connector to the relevant psu, a smaller amount will flow through the mobo connector, so one gpu would be getting power from two different psu's afterall. The pci-e slots can be rated at 75w, but they don't have to supply 75w. If the gpu wants say 120w, and the psu connector on the gpu provides a power path with 5x less resistance, then 5x more power will flow from the second psu to the second gpu, compared to the mobo to the second gpu. So for the sake of example, in this situation it would be 20w through the mobo, and 100w from the second psu.
Thanks mvagusta So just to clarify, in theory at least: Connecting my 620W to the mobo and primary GPU; and the 520W to the secondary GPU and all other peripherals (provided some load is put on the 3.3V rail) should be okay? Sorry for the paranoia but the last thing I'd want to do is toast a new GPU.
As the second GPU is getting some power from the 620W PSU via the mobo connector and card slot, that's a no-no. Devices you can run on the second supply are a bit limited; Peltier Water pumps Drives Fans Lighting
this might be a stupid question, but does the CPU need to be on the same PSU as the mobo? That might be a solution to the whole "balancing the loads" problem you have here: 620: Mobo + VGA + VGA 520: CPU + drives + water gear spread the rest out evenly to load all the rails.
But then I think technically the mobo (after all, that's where the CPU draws it's current) is getting power from both of the supplies? I'm really not sure cpemma is echoing what I've read elsewhere but I'd be interested to hear his thoughts on it.
