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+12v wattage? - Page 2

post #11 of 18
Quote:
Originally Posted by Nihilanth View Post
Your probably right but how much would you say 30+ amps on a single rail equate to on a dual rail? Can't quite figure out how 36 A(combined) on dual rails comes upto 24-26 A overall. Is there absolutely no hope of running my intended purchases even on stock? I admit i am a real noob when it comes to PSU's
There's no way of figuring it out unfortunately. The label should mention it, and even then, the label may be lying. On crappy power supplies there is no such mention usually because the manufacturer has something to hide. That's why you only buy units that have been reviewed professionally somehow, since those units would have been pushed to their limits by people who know what they're doing and have the tools to do it properly

Frankly though, I still think it'd be fine if you've had it for a while with your current system and it ran well. But it looks like a cheap unit, just by the looks of it, so I wouldn't put any trust in it personally.
post #12 of 18
You could figure it out by opening up the power supply and finding the datasheet for the +12V rectifier(s).

Otherwise, no.
post #13 of 18
Quote:
Originally Posted by Nihilanth View Post
Can't quite figure out how 36 A(combined) on dual rails comes upto 24-26 A overall. Is there absolutely no hope of running my intended purchases even on stock? I admit i am a real noob when it comes to PSU's
Yes there is hope, in fact there's a decent chance it'll work okay as your system shouldn't draw that much power, provided it's actually a decent unit that can safely provide the rated wattage or at least somewhere near it.

The reason that you can't just add up the 2 18A 'rails' is because they are not actually two separate 18A power supplies. In actuality, all the 12V wires are hooked up to the same source of power, with two overcurrent protection circuits protecting two sets of 12V wires. These two groups of wires with inline OCP's are 'the rails'.

What the 18A is actually specifying is how much (max) you can pull out of each set of wires that comprise each 'rail'. IOW, 18A is where the overcurrent protection is configured to 'trip' (i.e. shut off the PSU) for each of the two sets of 12V wires.

So, what the spec sheet means is just that you can pull 18A out of each of the two 'rails' ... but that doesn't mean you can successfully pull 18A out of both 'rails' at the same time. That's why most (quality) PSU makers will also specify a 'total' 12V amperage that the unit can put out across all the 'rails' simultaneously. Generally, this number is roughly 70-80% of what all the 'rails' add up to, so that's where I came up w/that number I quoted you.

You could try it dude, just go 'easy' ... no OC's or overvolts, ease into the stressful situations.

Whatever game you play first, make it an older game, and use v-sync to keep the GPU usage down. Run the game in windowed mode, and use some kind of voltage monitoring app (most mobo's come w/something along those lines, or you can probably use Speedfan) and keep an eye on the regulation on your 12V rail.

If you find the 12+ voltage dipping down into the 11.4V range, I would be inclined not to press the issue at that point. You'll need another PSU.

If, otoh, the voltage stays stable (i.e. what it actually idles at, which is hopefully around 12V), try removing v-sync, then try a modern, stressful game like Metro or Crysis ... and keep an eye on what happens with the regulation on the 12V circuit. Big dips in voltage = trouble.

Watching 12V regulation as you increase the load in this way is a bit of an 'eyeballing' method, but there's really no other simple way to 'monitor' the safety of the situation. Without having a UL number (these will always start w/the letter 'e' so if you can't see such a code anywhere on the label, we're pretty much out of luck) to try to assess the actual OEM/platform, this methodology is about the best you're going to get I'm afraid.
Edited by brettjv - 6/13/11 at 9:48pm
    
CPUMotherboardGraphicsRAM
xeon X5675 6-core @ 4.1ghz (1.29v, 20x205 +ht ) rampage iii extreme msi rx470 gaming X (the $159 budget king) 3 x 2gb corsair xms3 pc12800 (9-9-9-24-1T@1600MHz) 
Hard DriveOptical DriveCoolingOS
hynix 250gb ssd (boot), 2tb deskstar (apps),1tb... plextor px-712sa - still the best optical drive... corsair h8o v2 aio W10 home 
MonitorPowerCaseAudio
asus vw266h 25.5" (1920x1200) abs sl (enermax revolution) * single 70A rail 850w silverstone rv-03 XFi Titanium 
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CPUMotherboardGraphicsRAM
xeon X5675 6-core @ 4.1ghz (1.29v, 20x205 +ht ) rampage iii extreme msi rx470 gaming X (the $159 budget king) 3 x 2gb corsair xms3 pc12800 (9-9-9-24-1T@1600MHz) 
Hard DriveOptical DriveCoolingOS
hynix 250gb ssd (boot), 2tb deskstar (apps),1tb... plextor px-712sa - still the best optical drive... corsair h8o v2 aio W10 home 
MonitorPowerCaseAudio
asus vw266h 25.5" (1920x1200) abs sl (enermax revolution) * single 70A rail 850w silverstone rv-03 XFi Titanium 
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Reply
post #14 of 18
Thread Starter 
Quote:
Originally Posted by Shub View Post
There's no way of figuring it out unfortunately. The label should mention it, and even then, the label may be lying. On crappy power supplies there is no such mention usually because the manufacturer has something to hide. That's why you only buy units that have been reviewed professionally somehow, since those units would have been pushed to their limits by people who know what they're doing and have the tools to do it properly

Frankly though, I still think it'd be fine if you've had it for a while with your current system and it ran well. But it looks like a cheap unit, just by the looks of it, so I wouldn't put any trust in it personally.
bloody liars ..thanx for the heads up

Quote:
Originally Posted by brettjv View Post
Yes there is hope, in fact there's a decent chance it'll work okay as your system shouldn't draw that much power, provided it's actually a decent unit that can safely provide the rated wattage or at least somewhere near it.

The reason that you can't just add up the 2 18A 'rails' is because they are not actually two separate 18A power supplies. In actuality, all the 12V wires are hooked up to the same source of power, with two overcurrent protection circuits protecting two sets of 12V wires. These two groups of wires with inline OCP's are 'the rails'.

What the 18A is actually specifying is how much (max) you can pull out of each set of wires that comprise each 'rail'. IOW, 18A is where the overcurrent protection is configured to 'trip' (i.e. shut off the PSU) for each of the two sets of 12V wires.

So, what the spec sheet means is just that you can pull 18A out of each of the two 'rails' ... but that doesn't mean you can successfully pull 18A out of both 'rails' at the same time. That's why most (quality) PSU makers will also specify a 'total' 12V amperage that the unit can put out across all the 'rails' simultaneously. Generally, this number is roughly 70-80% of what all the 'rails' add up to, so that's where I came up w/that number I quoted you.

You could try it dude, just go 'easy' ... no OC's or overvolts, ease into the stressful situations.

Whatever game you play first, make it an older game, and use v-sync to keep the GPU usage down. Run the game in windowed mode, and use some kind of voltage monitoring app (most mobo's come w/something along those lines, or you can probably use Speedfan) and keep an eye on the regulation on your 12V rail.

If you find the 12+ voltage dipping down into the 11.4V range, I would be inclined not to press the issue at that point. You'll need another PSU.

If, otoh, the voltage stays stable (i.e. what it actually idles at, which is hopefully around 12V), try removing v-sync, then try a modern, stressful game like Metro or Crysis ... and keep an eye on what happens with the regulation on the 12V circuit. Big dips in voltage = trouble.

Watching 12V regulation as you increase the load in this way is a bit of an 'eyeballing' method, but there's really no other simple way to 'monitor' the safety of the situation. Without having a UL number (these will always start w/the letter 'e' so if you can't see such a code anywhere on the label, we're pretty much out of luck) to try to assess the actual OEM/platform, this methodology is about the best you're going to get I'm afraid.
Thanks for the detailed explanation...that was a truck load of information and it cleared quite a few of my doubts but a few still abound So like you say if it stays above 11.4V then should it be ok? Also how much do you think a 6850 or 460 pulls of the +12v rail? Read someone mention somewhere that its 25a for a 6850 which falls between your estimation of the 24-26a on my PSU. Is it true?

No man i don't intend to OC or overvolt my rig as long as i am using this thing and i mostly always use the V-Sync otherwise it almost always causes horizontal tearing on my BenQ G2200HD.

Incidentally games like Crysis and Metro are the reason why i am upgrading though i first want to get my hands on Dead Space 2 and Portal 2. Even though i have finished them before, i want to play them at relatively better settings especially Metro which was an absolute torture anywhere out in the open even on 1024*768 although i had cranked up the settings to Very High..i know silly me
post #15 of 18
A single 6850 would never pull 25A, such a recommendation would be for the entire system at full load, and even then 25A is kind of a lot for a standard system with a 6850. The 6850 is a 100-120W card, so you're looking at 10A at the very most for the card alone. A 460 is a bit more demanding, but it's still just ~12A at the very most.
post #16 of 18
Thread Starter 
Quote:
Originally Posted by Shub View Post
A single 6850 would never pull 25A, such a recommendation would be for the entire system at full load, and even then 25A is kind of a lot for a standard system with a 6850. The 6850 is a 100-120W card, so you're looking at 10A at the very most for the card alone. A 460 is a bit more demanding, but it's still just ~12A at the very most.
Oh alright..got the numbers all mixed up..glad you clarified that.

Btw slightly off topic, i took your advice and did a little research on the i3 2100 and it does seem to be faster than even a Phenom II X4 970 at times when it comes to pure gaming which is my main criteria. Went through a few benchmarks and it beats the phenom regularly but unfortunately i couldn't find any comparisons for games like BFBC2 and GTA4. Searched around, people seem to be recommending the i5 which is not an option for me. The absence of the 2 cores plus the fact that it can't be OC'd at all are the main roadblocks to the i3 destination. I know you asked me to research but since i can't find a definitive answer what would you opt for? Are there gonna be a multitude of games using more than 2 cores soon if they are not here already? Am i good for at least a year?

Also the TDP is just 65w which is equal to my e7200(i know..outdated ) compared to the 955 which is 125w. How much does the phenom pull of the +12v rail(amp wise)? Going i3 might help me out in the PSU department as well.
post #17 of 18
The difference is that you can overclock the Phenom and get an extra 20% boost in performance, while the i3 is stuck at its stock clockspeed due to Intel's BCLK dickery.
post #18 of 18
Thread Starter 
Quote:
Originally Posted by Phaedrus2129 View Post
The difference is that you can overclock the Phenom and get an extra 20% boost in performance, while the i3 is stuck at its stock clockspeed due to Intel's BCLK dickery.
damn man..now i am confused Saw benchmarks where the i3 edges the 970 so for the the 955 to beat it i have to OC it. Read in reviews that the 955BE doesn't OC all that well and 3.7-3.8Ghz is all that it reaches without throwing serious voltages at it and aftermarket cooling which brings me back to square one with the PSU and my budget. I get where you are coming from though, i3 is still a dual and it takes away the oc factor hence i am not completely sold on it yet.

Decisions..so many decisions..my head's starting to hurt
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