Will my PSU be ok for this graphics card??

grx · Feb 10, 2010

I decided to upgrade my old and low performance geforce 7100gs to a low performance evga 9400gt :doh:

. On the evga website it says it requires at least 300W power supply with 18A on the +12V rail.

So i opened my pc and looked at my AOpen PSU, it said "DC Output: 300w". "It should be enough", thought. I installed it with win 7 and played games like GRID (obviously with the drivers updated). It worked apparently fine. Only sometimes GRID closed unexpectedly (Could it be related? :eek:

). But after a week i noticed that the PSU has only 8A and 14A on the +12V1 and the +12V2 rail. I've heard you can't just add them to obtain how many amp it really has.

Thus, the question is: Is it enough for my graphics card?. Also i don't understand why is that electric current necesary on the +12V, considering the 9400gt don't even need external power¿?

*Uploaded the photo of the psu for you to check it.

Hope some expert can solve my doubt...

Frostmourne · Feb 10, 2010

That PSU is OEM junk. I would keep this PC as a media server and build a new one for 7 - your resources are not enough for GRID or 7 - not enough RAM or CPU power. As for the 9400GT, it depends on the model. Don't install it, that PSU isn't suitable.

Kipper · Feb 10, 2010

yep, a good quality Power Supply so very critical to system health and component longevity. you will find PSU calculators at most of the manufacturers sites.

Good advise above from Frostmourne, start a new build and I would recommend after you have the rest of your components identified then go to a reputable PSU site (Enermax, SliverStone, Corsair, to name a few) and pick up a PSU that will afford you future upgrades to boot.

Fumz · Feb 11, 2010

Hi grx,

The reason you need high amperage on the +12 volt rail is because basically everything in a modern computer runs off it it.

A few things to note:

Don't be deceived by PSU's that claim to have dual, triple and quad +12 volt rails; they're not. Yes, true dual rail PSU's exist, but they're rare, hard to find and a bit pricey. What you'll most often find is that the manufacturer has simply "split" the +12 volt rail. This isn't optimal because once slit, power cannot move back and force between rails if the system needs it... your conclusions were correct.

Don't be overly concerned with overall wattage. Makers sell insane PSU's these days despite the reality that most, if not all purchasers will never come even close to using all that power. http://www.xbitlabs.com/articles/coolers/display/system-wattage.html

What you want is a moderately priced PSU that's a quality build. There are only a few name brands where you basically just cannot go wrong: PC Power & Cooling, Zippy and Seasonic. For all the rest of the PSU's out there, you're going to have to pick the right model because, for example, while OCZ, Silverstone and Enermax do make some very good PSU's, they can and do also churn out some garbage.

It is always best if you do a little research on your motherboard. Just because you have a great board and a great PSU does not mean they will play nice together. This doesn't happen often, but it can and does... although admittedly it's less frequent these days.

Here's a list of PSU's to consider. There are others of course, but this is a list of hardware that's been thoroughly tested: Official XS Power Supply Ranking Phase I - XtremeSystems Forums

Pick one that has high amperage on a single +12 volt rail, that also comes with a multi-year warranty. Happy shopping.

krazymate · Feb 11, 2010

onest i wouldnt build a new machine theres really no point in wasteing your money on a new build when you just can buy a new PSU which is what ? 400W and will work fine
youy can pick them up in stores now for no less than 20 quid
thats if you didnt want to build a new system which i really dont see the point in doing
because you might already be happy with the one you got

Fumz · Feb 11, 2010

A $20.00 cheaply constructed power supplies is definitely not recommended. While CPU's, graphics cards and RAM get all the glory, the PSU is really the heart of any system... but sadly, it gets no love. If your power supply isn't sufficiently strong, sufficiently stable and able to provide clean power all that fancy stuff won't mean squat... voltage errors aren't easy to diagnose because they're not always easy to reproduce.

grx · Feb 11, 2010

well thanks. grid and win7 worked fine, but that's not what mattered to me. I just recently began to modify my pc, so i was wondering about the PSU. I noticed its quality wasn't good, so now i'm looking for one, not so expensive but with more wattage, and a good amperage +12V single rail.

Frostmourne · Feb 11, 2010

grx said:
well thanks. grid and win7 worked fine, but that's not what mattered to me. I just recently began to modify my pc, so i was wondering about the PSU. I noticed its quality wasn't good, so now i'm looking for one, not so expensive but with more wattage, and a good amperage +12V single rail.

Corsair HX 620w should be enough for your usage.

JonM33 · Feb 11, 2010

Frostmourne said:
grx said:

well thanks. grid and win7 worked fine, but that's not what mattered to me. I just recently began to modify my pc, so i was wondering about the PSU. I noticed its quality wasn't good, so now i'm looking for one, not so expensive but with more wattage, and a good amperage +12V single rail.

Click to expand...

Corsair HX 620w should be enough for your usage.

I concur. I have had a Corsair HX520 for 3 years. It has been reliable through all my upgrades and remains as quiet as the day I got it. Corsair was also cool enough to send me out some additional SATA power cables since the HX520 only came with 4 connectors.

sbrads · Feb 13, 2010

Another vote for a Corsair HX 520w. Reliable, efficient and quiet and it CAN share current amongst its 3x12v @18A supplies if needed (so Corsair say). The highest power I've seen it have to draw from the mains supply is only 115w though during an Intel stress test, with an overclocked 3.4Ghz E7300 C2Duo, 4Gb, Nvidia 9500GT, 3 HD, 2 DVDR/W type of system. It's gamer graphics cards that are the real power hungry devices in a system these days, and a basic card that runs direct from PCI-e is only going to use a few tens of watts.

pparks1 · Feb 13, 2010

I run a Corsair HX620 in my box and I have been very impressed and satisfied with this power supply. I don't think after using a modular power supply that I would ever go back to a non-modular power supply for my home machine. Keeping the wiring neat and tidy is a key element to a nice computer for me.

bobkn · Feb 13, 2010

Fumz said:
Don't be deceived by PSU's that claim to have dual, triple and quad +12 volt rails; they're not. Yes, true dual rail PSU's exist, but they're rare, hard to find and a bit pricey. What you'll most often find is that the manufacturer has simply "split" the +12 volt rail. This isn't optimal because once slit, power cannot move back and force between rails if the system needs it... your conclusions were correct.

I'm not sure that I buy that. People used to have trouble with the way some multi-rail PSUs were wired, when trying to use a pair of high-power graphics cards in SLI.

SLI and CrossFire Push Power Supplies to the Limit - CPUs, Boards & Components by ExtremeTech

I think that multiple small voltage regulators may be cheaper than one high-capacity one.

A 9400GT needs no external power, and consumes less than 40W max, so I'm pretty sure that it would operate in grx's system.

I have no idea whether a game like GRID would run tolerably at any settings on grx's system, with the upgraded GPU. Adding a $100+ PSU to permit adding a $40 graphics card sounds like a poor bargain.

Fumz · Feb 13, 2010

bobkn said:
Fumz said:

Don't be deceived by PSU's that claim to have dual, triple and quad +12 volt rails; they're not. Yes, true dual rail PSU's exist, but they're rare, hard to find and a bit pricey. What you'll most often find is that the manufacturer has simply "split" the +12 volt rail. This isn't optimal because once slit, power cannot move back and force between rails if the system needs it... your conclusions were correct.

Click to expand...

I'm not sure that I buy that. People used to have trouble with the way some multi-rail PSUs were wired, when trying to use a pair of high-power graphics cards in SLI.

So what's all this rubbish about multiple 12 volt rails?

Will my PSU be ok for this graphics card??

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