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Stupid question about 12volt rails.

Last response: in Components
January 16, 2011 7:03:29 PM

I am in the market to purchase a 600-800w PSU in the coming week. I currently have a Cooler Master Elite 360 case, so PSU size matters to me a lot. The current PSU I have installed is the Cooler Master eXtreme Power Plus 500W. It has 2 - 12V rails at 18A each. I upgraded the computer with many new parts recently, and I am currently on the edge of the PSU's power limits. Let me tell you what I've got. And then I have a stupid question to follow, LOL. :kaola: 

AMD Phenom X4 965 BE C3 OC to 3.8GHz on air cooling.
Asus M4A88T-M/USB3
4 x 2GB Kingston DDR3-1333
2 x 1TB WD Caviar Blue SATA2 HD
1 x Pioneer DVD-DL Burner SATA
1 x Zotac GTX465 1GB GDDR5 Memory

The Cooler Master PSU calculator says my system pushes approximately 488W, and I am running a 500W PSU... so I want to upgrade with something that has much more wattage and greater efficiency. But I have a problem with my current case. Right now with this tiny case, and this large video card, I have only 1/4 inch space between the video card and the PSU (luckily the video card power connectors are on the side and not the back or it would never fit). So I have been looking at other Cooler Master PSU's like the GX 750W, because it's size is exactly the same as my current PSU. The dimensions are 5.9 x 5.5 x 3.4 inch (150 x 140 x 86 mm). Anything LONGER will not fit, period.

Also I must mention that I am an American living in China, and I cannot find any PSU locally over 500W... they think 750W is insane or something and have to order it. So I will likely be ordering this from the Chinese NewEgg. The Chinese NewEgg only carries 1 Antec and it is too large to fit. They carry most of the Cooler Masters and Coolmax brand. So keep this in mind with regard to any recommendations you may have for me. My brand selection is quite limited as is my size.

Now for the stupid question. Is it more important to have one large rail? Or 2,3, or 4 +12V rails. In all my years of building PCs, this is the first one that required me to ask this question because of the large power requirement of this particular video card. I never ran SLI or Crossfire systems, and up to now I never had anything over the 9800GT. So stability and rails have never entered my mind. I always just pick something 100-200 watts more than they system will draw.

My current PSU has 2 +12 rails, but the one I am considering has one large +12v rail (+3.3V@25A, +5V@25A, +12V@60A, -12V@0.5A, +5VSB@2.5A)

What is most important for the voltage stability and system performance? Raw wattage on one rail? Or wattage equally distributed on several rails? I do not plan on running more than one video card this board only supports one anyways.

Any ideas would be greatly appreciated! :sol: 
a b ) Power supply
January 16, 2011 7:21:36 PM

Both antec and corsair have ps with a single large 12v rail. If you have no plans to use multple video cards, then the large single 12v rail is what I would get.
a b ) Power supply
January 16, 2011 10:37:41 PM

cooler master's extreme series is total crap. their other series are decent, but still not as good as antec, corsair, or seasonic, which are very good.

and coolmax is even worse it REALLY SUCKS!
a good 500w psu would do that fine. but not that cooler master extreme, because while cooler master did a decent job on all their other psus, they made total crap called the elite power and extreme power. they manage to sell these because people are like "yay its cooler master it gotta be good!"

so there ya have it LOL
Related resources
January 17, 2011 12:39:26 AM

Those "PSU calculators" are not very reliable, in part because
PSU manufacturers make a much larger profit margin on their
large wattage units.

In other words, they almost never underestimate!

> The Cooler Master PSU calculator says my system pushes approximately 488W

To be perfectly honest with you, 488W sounds WAY TOO HIGH
for the components you have listed.

See also what Newegg's specs say about the Zotac GTX 465:

i.e. "550-watt power supply recommended"

BEST WAY is to buy an Uninterruptible Power Supply / Battery Backup
with an LCD display that reports wattage in real-time, like this

Any good PC should be powered by a quality UPS anyway,
because reliable input power will prolong the PC's useful life.

Watch the UPS display during POST, because there is always a
current surge when a computer is just starting up e.g.
during HDD spin-up.

Also, test it with a full load too, so you can get an empirical
measurement of the operational range of your wattage loads.

When in doubt, a good rule of thumb is to target 50% utilization,
on average: most PSUs reach maximum efficiency at or near 50%,
and that target will leave lots of room for future expansion, and
for the temporary peak that happens during startup.

p.s. I ditto the Seasonic, Antec, Corsair PSUs, especially Seasonic.
If you have already decided to upgrade --
"I am in the market to purchase a 600-800w PSU in the coming week." --
that's a good range: you can get very good deals from Newegg
for most of the quality units in that range.

This Corsair 650HX is an excellent unit with a single +12V rail:

"Up to 85% energy-efficiency under real-world load conditions"

(Unless we already know the history of a certain product -- from reading reviews
or direct experience -- we avoid "bargains" on motherboards, RAM and PSUs
because those are the single most important components, besides the CPU.)

Hope this helps.


January 17, 2011 1:47:49 AM

I thank everyone for their input. Seems my biggest problem is a case limitation more than whether to get more rails. If I get the Corsair PSUs, especially the 650HX (150mm(W) x 86mm(H) x 150mm(L)... I will need to take off the case on my video card and shave the PCB or remove the outer case from the power supply to make anything other than Cooler Master fit. I can't go any longer than 142mm without it being too tight against the video card. Cooler Master designed this case like this on purpose probably, knowing that if someone wanted a single large video card, they need to buy the matching Cooler Master power supply.

I really don't want to buy another case just to accommodate this either, I picked this case because of the tiny size and use it in my bedroom as an HTPC that I can play all my games on. I could put my 9800GT in there which is much shorter, but then I don't need a bigger power supply, and Crysis will suck again. I am getting dizzy now, Lol.

Also, in the Chinese NewEgg, I don't got so many choices like the US.

Here is all their Corsair PSUs... but I can't really afford to spend more than 800 RMB ($120) and I cannot afford to change cases or video cards at the moment.

And this is the ONLY Antec they sell: and it won't fit in my case because of 1/8 inch clearance issue.

These are the only Seasonics I can find:

And this is the Cooler Master I was looking at, because it is 750w and is the same size as I have now:

I can read Chinese and know all the differences in these... but it seems I can't find any information on the Seasonic dimensions. And I know the Corsair and the Antec won't fit. Sounds like I am screwed for now. And if I take the 9800GT out of my other PC and put it back in here, my other PC only has a 450 PSU and and can't handle the new video card. I am between a rock and a hard place.
January 17, 2011 1:53:54 AM

Also, the Coolmax RM1000B is cheap, and it will fit

But everyone keeps telling me they suck. All the Chinese shops swear by them. I can pick up the Coolmax 1000W for $60 here on sale for Chinese New Year at my local shop. But I gotta order it 2 days before I go. But I don't think I want to go with it because my US brethren say they suck a lot, LOL.

And also note, I need all the cables to come out of one side. Modular may also interfere with my video card. I want to bang my head on the wall now. :cry: 
a b ) Power supply
January 17, 2011 1:56:55 AM

they suck they suck they suck they suck they suck theysuck they suck they suck...

i think you get the point, and yes i bought one once too lol. it hasnt died yet, maybe because i only used it for like a week its sitting on the shelf iwth my other like 500 psus lol :) 
January 17, 2011 2:03:16 AM

The 500W eXtreme power I am using now hasn't caused me any problems yet. I am just worried that my system is drawing too much since I upgraded. The original CPU was a Core 2 Duo 65W... Now I am running the x4 965 @ 140w. Since the video card also sucks a lot of juice, I am concerned. But I have run this setup for a month and never had a single issue.
January 17, 2011 2:05:00 AM

PS, I do have the C3 125W revision, but I'm running it at 3.8GHz... so I just estimate the 140W.
a b ) Power supply
January 17, 2011 2:06:09 AM

yes the best reason to be worried about it is because its not considered to be the most honestly rated psu. actually, i own one of those, and upon opening up the psu, i checking it out to see besides using a cheapo fan and not having pfc, its a decently made psu. but i wouldnt trust it more than 450w continuous for a long time!
January 17, 2011 2:21:58 AM

I want to ignore the PSU calculator. Let's try to add it up on here without buying meters and such...

Now, Nvidia recommonds a 550W PSU when using the GTX465 or 470.

What is the stock power of the Zotac GTX465? It has 2 PCIe 6 pin connectors.

Also, I believe the mainboard ASUS states is around 22-30W.

I have the Phenom x4 965 BE clocked at 3.8GHz (possible 125-140W), it is the C3, but I am not running it completely stock.

I have 4 - 2GB low profile Kingston DDR3-1333 (how much wattage here?)

I have 2 - WD 1TB Caviar Blue disks (how much wattage here?)

I have 1 - Pioneer SATA DVD-DL burner (how much wattage here?)

I have 1 - 120mm case fan (wattage from this is negligible.

No additional coolers or PCI cards, and no future plans to add anything else ever. The case is the Cooler Master Elite 360, and I use it for an HTPC and a gaming PC. In a year or 2 if I upgrade, I will likely change everything. Right now I can't afford another case and don't want a huge ATX tower by this little 24" screen, LOL.

I don't think I am leaving anything out. What do you think the total system draw is while playing Crysis Warhead or Bad Company 2?

January 17, 2011 2:27:24 AM

The Cooler Master PSU calculator suggests 488w... but I am imagining these numbers as a worse case...

CPU 140w
MEM 20W total (guessing here)
HDDs 20W total (guessing here)
DVDR 20W total (also guessing)
GFX CD 200W possible (guessing again)
So I see the guessed wattage around 430. But perhaps I am way off... :D 
January 17, 2011 2:39:31 AM

1965ohio said:
I thank everyone for their input. Seems my biggest problem is a case limitation more than whether to get more rails. If I get the Corsair PSUs, especially the 650HX (150mm(W) x 86mm(H) x 150mm(L)... I will need to take off the case on my video card and shave the PCB or remove the outer case from the power supply to make anything other than Cooler Master fit. I can't go any longer than 142mm without it being too tight against the video card. Cooler Master designed this case like this on purpose probably, knowing that if someone wanted a single large video card, they need to buy the matching Cooler Master power supply.

I'd strongly recommend avoiding Coolmax and Logisys. I had a Logisys recently that was horrible, just horrible. So I studied hard on PSUs - something I'd never done as they were always an afterthought - and I bought the Cooler Master Silent Pro M 850 watt. Their top-of-the-line Silent Pro Gold line is vastly overpriced, especially compared to their 2nd best Silent Pro M. Besides, the Golds have 90+ amps ... you could start a car with a Silent Pro Gold, I don't want that. The Cooler Master GX line looked great, too ... almost got the GX-750 but found a killer price on the M 850.

If you want Cooler Master, I'd recommend choosing a GX or Silent Pro M:

Other stuff I picked up ... the number of coils is not important. 'Multiple coils' sounds good because it seems to jibe with multi-core CPU, but that's not true. And one article actually said the heavier in weight PSU is almost always the best. Go figure. Makes sense, because that crappy Logisys I bought is so light I can't even use it as a paperweight.

Best solution

a b ) Power supply
January 17, 2011 2:46:41 AM


Nvidia says that card can eat up to 200(no game will push it that hard, maybe furmarks) watts on its own. So depending on the rest of the system, you will determine power use.

If you want to know your power use get a kilo-watt or similar power utilization meter(it looks like a digital timer, but it tells you power use). Remember that will also take into consideration power losses in the power supply so actual power will always be lower then that it shows, but running a power supply at high loads is stressful on it. Half way is best for it(efficiency).

Most multi rail psus are just a single rail unit with overcurrent protections enabled. This allows then to make the ATX specs. They all draw from one big rail, but prevent a user from plugging EVERYTHING onto one molex and smoking the wires.

It is important to know that 12 volt capacity is the primary thing to look for now days. You can have a 500 watt psu with only 360(your current power supply) watts on its 12 volt or another one with 450-480 on its 12 volt rail.

Also higher efficiency power supply units run cooler and quieter.

For example.

This system has a HX850. I know its overkill.

With 4 sticks of memory(other 2 are on loan) and a clock speed of 3.5 on my I7 system with 4 hard drives and a 5870(188 watts as per ati) draws an idle power of about 202 watts(from my ups - my other system that is on here too).

Prime it up and I am up to 312. add Starcraft 2 replay at 8x 320-366. Without prime the same replay is 296watts.

This is all with my other system running too(its low power, i5 750 + 5770 + 300 watt psu, yeah 300 is more then enough for that system.). I will have to get the exact numbers with it only so they can be taken off the numbers above(about 50-60 watts).

My point is, i do not think you need a massive power supply for most systems.

Newegg has reviews for that coolmax unit

another option? read on

Your current psu has a limit of 360(30 amps max) watts for both its rails combined since they are shared.

Corsair 600 watt unit(but its more like a 500[480 watts or 40 amps on its 12 volt rail] watt unit from its specs). I still think its got the goods. and the 30c operation temperature should be no problem with your cases vent for the power supply.

anyone else have an opinion on it?

If you are not getting a new psu right away, I have a X4 955 @ 3.7(3.8 needs over stock voltage on mine, so i do not run it that high). I can add my 5870 to it to get you some approx power measurements.

Hope the long read gives you some useful info...
a b ) Power supply
January 17, 2011 2:52:50 AM

there's about 20 things wrong with what you said but we won't go on to that just the thing about the weight. How you going to feel the weight when buying online?

You can't feel weight online? i never knew that:p 9(i had to) High efficiency power supplies are in fact getting lighter :)  yet better.

I bet starting a car with a power supply would just kill it :) 
January 17, 2011 2:56:09 AM

The case size and video card size are whats truly killing me! If I just had an inch to work with, I probably would just buy the Antec or Corsair 750w without making a post, LOL :D 
a b ) Power supply
January 17, 2011 3:00:13 AM

I feel your pain on the small case:) 

January 17, 2011 3:05:15 AM

I went with this case in hopes of staying small, but not too small like ITX! I turned off my overclock and am running stock speed until I can sort this out. But I have to be careful what I buy. I have to order it, and if it don't fit... there are no refunds or exchanges for other products in China. Once you buy something, you are stuck with it!
January 17, 2011 3:14:12 AM

If I buy an Antec or something longer than 142mm... I need to take the PSU out of it's box and custom mount it somehow. Haha. Gotta love little cases and big video cards. I didn't take this into consideration when I bought the case last year and ran a Core 2 board with a 9800GT... but it was getting stale for my newer games.
January 17, 2011 4:17:26 AM

Take a look at this pic... (not my cards, but same case...)

Now imagine trying to use a deeper PSU and have a GTX465 butted up against it or not fitting at all. Now I am regretting choosing this case. :cry: 
a b ) Power supply
January 17, 2011 12:23:15 PM

newegg has good reviews for that psu. Off course they want to sell it.

they also have bad reviews. Its not like they remove bad reviews, i have seen many bad reviews over there.

I still think the corsair 600 watt builder series should fit the bill.

1965ohio, the OCZ MODXSTREAM(552 watts or 46 amps on its 12 volt rails) 700 should work, BUT it is MODULAR and the cables may get in the way. I have the GAMEXSTREAM 700, but find it to be loud.

Newegg reviews. And yet there are 1 and 2 egg reviews, guess newegg does not sensor those after all.

Your case does take standard atx sized power supplies. It is just that some higher wattage units are larger(longer). The HX 850 comes to mind. It is not fitting to the standard atx dimensions(length).
January 17, 2011 12:42:46 PM

Nothing longer will fit because the GTX465 is already 4mm away from the 140mm PSU. Doesn't matter now. I swapped out cases with my Intel build. I am still using the same PSU, but I will buy a new one this week. I am using a Chinese case made by Lian-Da... knock off of the Lian-Li's. It is full tower with the PSU mounted up top. I can fit any size now. I just really didn't want this larger tower sitting as my HTPC, but no choice since I want to run the GTX465.

I will get the Corsair or the 750w Antec from the Chinese NewEgg possibly. If I got the money I'll just buy a modular 1000w supply just in case I want to change boards and run SLI in the next year or 2. I only got the Cooler Master eXtreme 500 because the dealer gave me a discount on the case and PSU together. But since I moved it into a large case, I find the wires are all too short and I cannot route them in a nice way. Looks like $hit. The Intel build is using a Chinese power supply called Huntkey DH6... it is only 400W but it is very quiet, very stable, has long wrapped wiring, and plenty of connectors. The modular would be best since I am using this case, cause I'm obsessive about the cable routing being efficient and pretty too, lol :p 
January 17, 2011 12:47:09 PM

Best answer selected by 1965ohio.
January 18, 2011 10:04:52 AM

there's about 20 things wrong with what you said but we won't go on to that just the thing about the weight. How you going to feel the weight when buying online?
So you're new to computer power supplies, eh? Well like I said, I did my homework so I can help.

1) Though many manufacturers like Cooler Master and Antec list the net weights of their units in the specs, nobody said it was practical to shop for a PSU based on weight. We merely pointed out weight is a proven indicator of quality:

"Herein we document a very simple way to estimate the quality of a computer power supply by the weight. We measured the weights of 38 standard ATX power supplies of different wattages, models and manufacturers. The weight data were then correlated with the current price and wattage on the label" . . . . . "This study clearly confirms an empirical knowledge: the quality of a power supply can be estimated by its weight."

2) My point that Multi-Rail configurations have no advantage, make no difference, well ... this very forum pointed that out almost two years ago:

3 Though many mid-size and larger vehicles require up to 200 amps to start, the fact many smaller cars can be started with 75 to 150 amps is pretty common knowledge for a mechanic. And like I said, the Cooler Master Silent Pro Gold units have 90 to 100 amps. So no luck there either.

But starting a car is off the beaten path really, and I want to keep this simple for you. Understand that you can gather knowledge all by yourself! Try this: go to "" on the Internet (that's a "search engine"). Type in a few important terms (words), and click enter. There's lots of information available in the sites that appear on the next page. But you have to take the time to read them ... no more short-cuts!


So .... ready to roll out your other 16 "wrong things" Skippy? :wahoo: 
a b ) Power supply
January 19, 2011 12:38:33 AM

Well, here it is, the power stats for the closest system I have.

Gigabyte 770T USB3
Phenom X4 955 @ 3.7 - stock voltage
1TB Drive(Seagate)
2 Sticks of memory.
AMD 5870(188 watts MAX per ati, close as I have to a GTX 465)
HP DVD burner
Antec 300 case(like it matters)
OCZ Z series 550 watt 80+ Silver

Stats at the wall so actual DC output is lower(15-20%[maybe even more at idle, as in more power waste since its not in the 20% range spec'd by 80+] power depending in load).

January 19, 2011 2:59:45 AM

I can't stand when people post replies about how google is your friend. Did you know when you google this kind of thing it just takes you to a forum, like tom's that helps answer your question? Maybe someone else is searching this problem and will end up on this thread here and their question will get answered. So google is your friend as long as someone else has asked the question before. The tech sites aren't directly clear of the benefits of multiple rails versus a single large rail. Real world advice for a specific situation is why people ask questions here.

Also, if you shopped for electronics by weight, the companies would just make the box heavier. That is like Intel selling the netburst CPUs based on raw clock speed not performance. Weight is not an indication of performance. It could be an indication of better materials or better workmanship, but not performance. Electronics are getting smaller and lighter everyday and the performance is getting better.
a b ) Power supply
January 19, 2011 3:19:05 AM

i think it was deer (the worst psu manufacturer) that caught on to the wieght thing; for a while they put magnetic weights on the inside of the psu casing to make it seem heaver.
January 19, 2011 6:21:37 AM

Well, my local guy doesn't have anything over 500w in stock right now... so anything I want will have to be ordered. The other local stores want to rip me off. Looks like I will have to order from the Chinese NewEgg or Taobao (like the Chinese eBay). For around $100-130 USD I have it narrowed down to a few models. Right now I am trying to figure out which place to buy it.

The Chinese NewEgg always packs the cheap things well, and doesn't pack expensive things at all. I already am having trouble with them over a Western Digital WD1001FALS HD. They didn't pack it well, but it worked fine for 3 months. Now it has SMART errors with too many bad sectors warning, and it sounds like a lawnmower. I tried to contact the Chinese NewEgg and they basically told me I am $hit out of luck and need to contact WD. WD tells me the HD is fake and the SN on the top and bottom don't match their records. They say it is either an OEM part with no warranty, or it is fake. So I am stuck with a black edition WD hard drive which cost too much, and has no 5 year warranty, or any warranty at all. So I am weary about the Chinese NewEgg at the moment.

Also in China, there are no refunds. If something doesn't work, you can only swap it for the same thing or next model up and pay the additional. Even if it is defective, no refund... exchange only.

The field has been narrowed down to the OCZ Fatality 750w, Seasonic M12D SS-750, Antec TruePower 750, or the Corsair GS700. I can get the Cooler Master GX750W, but I don't like the reviews I am seeing about heat and noise. So I will have to give this a good 2 or 3 days to make a decision.
January 19, 2011 6:27:06 AM

The OCZ, Antec, and the Corsair are all over $120 in China. But the Seasonic one I listed is only $90...
a b ) Power supply
January 20, 2011 12:47:38 AM

yeah lol :)  they should get sued for that :)  but they probably wouldnt answer the phone, too busy scheming about how to make the psu even cheaper! :p .

ps, i like your sig:
Join The Army, Visit exotic places, meet strange people, then kill them
January 20, 2011 12:57:51 PM

Do you mean Huntkey? That is the most famous brand here in China. And they have a gold and silver now. Huntkey X7 900w.
a b ) Power supply
January 21, 2011 2:01:08 AM

1965ohio said:

That's they Huntkey x7. Cost about $150

I notice something interesting from reading a review about some of the Huntkey power supply units. They use some components that are not well enough cooled to put up with running on the 110-120 volt power found in the western world.

Could this be the issue it self?
This power supply uses one D15XB80 rectifying bridge in its primary stage, which can deliver up to 3.2 A (rated at 25º C) without a heatsink installed, which was the case. If Huntkey had attached a heatsink to this bridge its maximum current would be 15 A at 100º C. This is definitely something Huntkey should have done, because this bridge is limiting the maximum amount of current this power supply can deliver. At 115 V this unit would be able to pull only up to 368 W (115 V x 3.2 A) from the power grid; assuming 80% efficiency, the bridge would allow this unit to deliver only up to 294 W without burning this component. This is ridiculous and a hint that something is wrong with the project from this power supply.

Damn things may work better over there after all.