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2 Power Supplies?
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(28 posts, started )
2 Power Supplies?
I just blew my power supply and am looking for a replacement. But i have a 350W supply in my old computer and was wondering if for example i could buy another 350W supply and use them together as it would be cheaper than buying a 700W supply.
You could but I bet your 350W PSU isn't 350W anymore (PSU's are wearing out)
Why do you pretty much need a 700W supply ? I think <500W would do it. Buy a good brand (FSP,Corsair etc..) 450W and it will be fine i guess
I want a 700 because my 500 blew. I think my gfx card made it go, i was playing GTA 4 and i started getting FPS drops just before it blew, it was my first time playing it too. Also the card says it needs a minimum 500W supply.
If your 500W blew, it's really... chinese 500W.
A good branded 400W PSU can run a quad core with a 4870 without any problem. Blowing a PSU doesn't mean it wasn't enough, it could be many things like faulty components inside the PSU and stuff.
I am pretty sure you don't need 500W, let alone 700W. Just get a quality PSU (Corsair for example) that fits your budget.
No... I don't think that is possible. If it is, it is not worth the time, and workings. I saw a BFG 550 Watt for $22 Canadian. That should have more than enough amps on the 12V to run any single card GPU... These 350W that you are looking at may not have the amperage to outrun good modular 500 watts like an HX500... These things are rather efficient. No names just don't get the job done; if they do, they are a hazard for hundred dollar cards, motherboards, CPUs etc...
Guys, he could easily have blown a 500wt PSU depending on his system specs that are not listed. If its "an old dinosaur" than likely you guys have valid points that it shouldn't have blown; although PSU's do die eventually...

Anyways, I have a 650wt PSU at the brink of its limits. I've turned down 2gb of free ram because it would quite possibly push me over the limit. As is I need to watch what do; so its quite possible to run over the limits of a PSU. Even without it being 'Chinese'

Although as RevengeR said; it's not only the load that can kill the PSU. Time wears them down, obvious certain electrical issues; blackouts/brownouts/surges are can effect them as well. I am not an expert but that is my 2c.
Quote from blackbird04217 :Anyways, I have a 650wt PSU at the brink of its limits. I've turned down 2gb of free ram because it would quite possibly push me over the limit. As is I need to watch what do; so its quite possible to run over the limits of a PSU. Even without it being 'Chinese'

So you have one those Core i7 + Quad SLI systems overclocked to the max then?

The amount of power needed is grossly overestimated by many people. I would say around 500-600W is enough for most systems. Only really really high-end systems go over that.
You can mix the power supplies, but you have tou avoid it when possible, and in your case, is possible. Besides, I would never use a 350W old psu in a new computer.
450W is just in the limit of a new and powerful computer. I have a 600W Zalman and I use around 460W at full load (specs in my signature). And Watts is not the main thing in a PSU (it's like the megapixles in a camera). The 12V lines and their amperage goes first
One last thing, avoid the cheap and crappy ones. PSU is more important than people thing...

Quote from geeman1 :So you have one those Core i7 + Quad SLI systems overclocked to the max then?....

For that you need at least a nice 800W psu in order to keep the system safe. Keep in mind this is like a car. Take a Renault Twingo to the highway at 150km/h for a long trip, constant speed, and it will be hot, the fuel compsuption will be "huge" and the engine will suffer. Do the same with a 911 in 6th gear and you'll be fine.
I was gonna do this, run 2 PSU's as i only have a measly 250w one, i had it all planned as well, one to run the HDD's and DVD drives and the other to only run the GFX card, but then i looked and discovered that my case cannot hold 2 PSU's as there isn't enough room!
Quote from geeman1 :So you have one those Core i7 + Quad SLI systems overclocked to the max then?

The amount of power needed is grossly overestimated by many people. I would say around 500-600W is enough for most systems. Only really really high-end systems go over that.

No;

680i SLI
Core 2 Duo (E6600) at 2.4ghz (no overclock).
GTX 280 OC
8800 GTS XXX'
500gb HDD
DVD Drive
TV Tuner Card

Cooler Master 650wt PSU;

A few USB connections.

Anyways; my voltage levels are very close to what I'd rather them not be. I've been told by several people whom I consider trustworthy sources; good friends that know a bit about hardware side of things what values should be as I compared them with what they are. I should expect to see positive values with a decent range instead of negatives for my +3.3v and +5v.

My voltage values;
+3.3v = 3.18v (-.12)
+5v = 4.82v (-.18)
+12v = 12.04v (+0.04)
For those interested i have a core 2 quad Q8300 and a 9800GT 1GB DDR3. The power supply came with the case which is only a month or so old. I read on the gfx card box that it requires a minimum 500W PSU which is why i thought it would be better for me to get a more powerful PSU as a replacement.
Quote from blackbird04217 :No;

You might be on the limit for your PSU, but far from the limit of a good Corsair, Thermaltake or Chieftec PSU, most of which are really CWT units underneath.

P5Q DLX
Q9450@3.6GHz (66% OC)
4GB RAM CL5, 1066MHz at 2.1v (A Corsair CL4/800 module paired with an OCZ CL5/1066, so the Corsair is OC'd a bit)
4870X2 + 4870 (both stock clocked)
XFi Elite Pro
2 x 1TB Barracuda ES.2, 2 x 500GB Barracuda 7200.11, 1 x 400GB Barracuda 7200.10, 1 x 250GB Barracuda 7200.11 (yes, that's 6 HDDs)

All easily powered by a Corsair 620HX, barely even touching 450W in GTA IV according to my - admittedly not terribly reliable - wall plug power meter.
Quote from morpha :You might be on the limit for your PSU, but far from the limit of a good Corsair, Thermaltake or Chieftec PSU, most of which are really CWT units underneath.

Idk what "CWT Units" are/mean. And sure I don't have one of those brands, but when I built my PC I did the research and the PSU I bought seemed to have great reviews for a 650wt which is why I went with it. I understand that the PSU is currently limiting me from my upgrades, but I was making a point that the OP may have been running with specs that pushed his PSU overboard. I mention that based on his OP and the way some remarks were made saying that he shouldn't have used anywhere near that.

Looking at his specs a few posts up I would guess he'd have been within safe limits. Which is where I took a guess at PSU age or other PSU failure.


EDIT: Your wall plug power meter may indicate the watts taken from the wall, but it doesn't display the voltages values on the rails, which are quite important. (Another speculation) I do believe that it is very possible to use too much of a single rail; like the +3.3v it would be possible to use too much from that and the PSU could fail to produce the voltage needed. Anyways, the wattage doesn't refer to how much is coming from the wall.
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Either way, this is a little of the topic since the OP was asking about 2 PSU's instead of buying a more expensive 700wt. On that topic I would guess (I do not know this I am speculating) that two 350wt PSU's does not equal one 700wt PSU. But for his knowledge I do believe using 2 PSU's are okay as long as each device uses the same PSU. IE; my gfx cards each have 2 inputs, so both power inputs would need to be attached to the same PSU. That is my own assumption more than anything. Anyways good-luck BenjiMC.
CWT is Channel Well Technology, the company that manufactures the internals. Corsair, Thermaltake, etc. just do their own modular cable management system and so on, the actual PSU is often the same.

Regarding the voltage/amperage: The HX series, as far as I know, is actually a single-rail unit. Normally you get several rails from one rail with over-current protection circuitry splitting it into, let's say 18 amps per rail. The HX can, in theory, dish out 50 amps on it's single 12v rail and still provide sufficient voltage on the 3.3v and 5v. How long it can endure that is another question

On topic: 2 PSUs are inefficient and loud(er), but generally possible. There are two problems I can think of right now:
  1. Grounding issues, both PSUs need to be in contact with a conductive surface of the case and so do components connected to either PSU without a GND (the black wires on a 4 pin molex). Interference is possible but should not occur if both PSUs are grounded properly.
  2. Switching the second PSU could prove difficult, at the very least you would need either a relay or small circuit.
All in all I wouldn't recommend 2 PSUs unless the 2nd one is for an electrically detached device, such as a pump for watercooling or a peltier element.
I run my HD4870 1GB OC and slightly oc'ed Intel E8200 and some HDD's and regular stuff - 500w. Lots of headroom left too. Also, u cant mix PSU's that easily. Just to use them separately (never use 2 different on 1 card - example: 2 PCI power slots). U kinda should build them up on 1 unit.
Quote from blackbird04217 :My voltage values;
+3.3v = 3.18v (-.12)
+5v = 4.82v (-.18)
+12v = 12.04v (+0.04)

Those voltages don't really indicate that you are on the limit of your PSU. It just means that the PSU has those voltages running. The voltages don't drop linearly as you use more power, your PSU could have those voltages even if you used half the power you are using now. Some PSUs just have voltages little under or over the intended value, but as long as they are within the tolerance it's fine (5% iirc).

As for the OP. Seeing your specs I can say you don't need 700W. Just get a quality PSU with around 500W and you are fine.
Quote from blackbird04217 :No;

680i SLI
Core 2 Duo (E6600) at 2.4ghz (no overclock).
GTX 280 OC
8800 GTS XXX'
500gb HDD
DVD Drive
TV Tuner Card

Cooler Master 650wt PSU;

A few USB connections.

Anyways; my voltage levels are very close to what I'd rather them not be. I've been told by several people whom I consider trustworthy sources; good friends that know a bit about hardware side of things what values should be as I compared them with what they are. I should expect to see positive values with a decent range instead of negatives for my +3.3v and +5v.

My voltage values;
+3.3v = 3.18v (-.12)
+5v = 4.82v (-.18)
+12v = 12.04v (+0.04)

You are nowhere near the limits of a 650W PSU with that setup.
Well, I am near the limits of my 650wt PSU, as you can tell from the voltage levels that I've collected information from. I should be higher than the specified, not lower. So a different 650wt PSU might tell a different story, however I have a > 2yr old PSU that rarely ever shuts off - it is likely to wear and as I said, I won't be upgrading my ram, which I want to as it is the performance bottle neck at this time, until I get a new PSU.
99.9% of the time the power supplies that come with a case are garbage. even if they do supply enough power where it counts, chances are it won't be good, clean power.

With a C2Q and a 9800 you will be fine with any quality 500 watt PSU. look at 500w PSU's with either a 30-35A 12v rail, or dual 20-24a 12v rails (2 x 22A 12v rails will give you about 32A total with 12v). Those 2 components probably draw ~10A on the 12v rail, each. That is 240 watts right there.

If you give us an idea of your budget then maybe some specific PSU's could be mentioned. i.e. a quality 500w PSU will cost the same as an adequate 700w. you might consider adding in several new hard drives. in that case the 700w might be better.


Something from Enermax, PC Power and cooling, Antec, OCZ, Seasonic, Fortron/Sparkle, Corsair are usually a good unit. (HERE is a very comprehensive list-probably TMI, but interesting if you are interested in computers--you can pretty much look at PSU's at a store like Newegg and then search in that thread for it and see where it stands)


When it comes to PSU's, its not the watts, its the amps you are interested in. in many cases a quality 500w power supply will be better than a cheapo 800w for your application because it has the same or higher amperage where you need it. There is a lot of marketing jargin you have to see through to tell if the PSU you are looking at is really good, with the exception of a reputable company. Some PSU's are rated by the MAX output, which is not the same as what they can continuously put out 24/7. Chances are a correct PSU for your hardware is also more efficient and you will not be wasting power. if you go out and buy a 1kw PSU that says its 85% efficient, it is probably only 85% efficient when it outputs around 750-850 watts. at 350-400 watts it might only be 60% efficient (there aren't exact numbers, just a ballpark example). this means that to get 400 watts to computer components you are drawing 650+watts at the wall. If you had a 600watt PSU that is 80%+ efficient around 400 watts you would only be drawing 500w from the wall. the efficiency rating is how effectively power is converted from Ac to DC. Also, power supplies lose a certain percentage of their output every year just from wearing out. Most will lose 5-10% of their power output per year, so buying the bare minimum might not work out in a couple years.
Well, i am flat broke so i only have around £20 to spend on a PSU right now. I know that won't get me a quality long term PSU, i have seen some in shops for around £50 which look pretty good. I will be adding a 1TB Sata hard drive later on also which will make it three in total (1x 80GB IDE 1x 200GB Sata).
Quote from blackbird04217 :Well, I am near the limits of my 650wt PSU, as you can tell from the voltage levels that I've collected information from. I should be higher than the specified, not lower.

Being over the specified voltage is not any better. Computer parts are designed to work with the specified voltage and on the ideal situation you PSU would supply that exact voltage. Going over or under is a bad thing. There are certain tolerances that the voltages are not supposed to go over. The little drops you have are within the tolerances. It could just be that the PSU was not manufactured with high quality parts so it the voltages differ from the ideal a little. That does not indicate that you are on the limit. If you had dramatic drops that would be another thing, but those voltages you have are well withing the normal operation tolerances.
#25 - STF
Quote from morpha :
  • ...
  • Switching the second PSU could prove difficult, at the very least you would need either a relay or small circuit.

You mean switching it on, or..? Can you elaborate a little on that?

If just for switching on, can`t he use a wire, a bobby pin or something steady to shortcircuit any black and green wire contacts from the 20/24 pin connector (goes to motherboard)?
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2 Power Supplies?
(28 posts, started )
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