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Question and dual 12v rail PSU and amps

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January 31, 2007 6:46:48 PM

I just got a 400w psu for my dell, it has dual 12v rails 1 at 15 and 1 at 14 amps for a total of 29 amps.

It came with a pci-x connector for my 1950 pro.

Will the psu connector draw power from both 12v rails to get the full 29 amps for the video card?

The psu is 2.01 or whatever complaint it says.

heres a link to the psu:
http://www.startech.com/Product/ItemDetail.aspx?product...

i had to get this one cause i have a dell 8200.
My old p/s works fine btw, but im stretching it thin i think.
and i dont have hardly any components in the case.
I know everyone is gonna say more power more power,
but if my 300w psu is working fine, im hoping this will
be perfect.

Thanks in advance!
January 31, 2007 7:27:33 PM

A peek at the label shows us the OEM is ATNG who also sources Enlight, Rosewill and Coolmax. It is suspiciously identical to these coolmax units, the CA-400 and the V-400...

Hmm, I am pondering... for your system a 20A would be recommended but can't say I would get either of those coolmax units for it.
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January 31, 2007 9:20:14 PM

Wow, that's what you picked up? Did you really pay $94.99 for it? That's crazy. Are you sure that this is one of the only power supplies that will work with your old Dell? That's brutal. But yeah, 400W should be enough for that card in your system. A card like that probably needs something like 400W and 20A on the +12V rail, combined. However, you don't just add the two rails together to get the total amperage. You have to divide max wattage on the rail by the rail value, i.e., 384W/+12V = 32A. I'm not sure what that Startech one is since they don't say max wattage. But anyhow, if you knew it, that's how you'd do it. Is the motherboard in that Dell proprietary or something, so that no other PSU will work? That's too bad if so. You could have gotten something better for the same amount of money. But in the end, you're probably ok.
February 1, 2007 10:59:50 AM

nah i paid 50 bucks for it, free shipping.

its 375 max, so im looking at 31 amps.

Cool beans btw its an agp, its one of the reasons i picked this psu,
cause it offered proprietary dell fitting, and had a pcie connector,
so I didn't have to use that splitter and use my 4 pins.


i installed it last night, and it works fine. my bench scores are low, and people kept saying it was cause of my shitty psu, so i swapped it out, and they are the same.

oh well atleast im safe now, the system is OLD, and the old psu was saturated in dust and thick gooey smoke filth from cigarettes. haha.
So it was probably for the best i swapped it out.

I recently cleaned the system out well and re did the cpu fan and heat sink with new compound and stuff. so I think its good to go for another few years.
February 1, 2007 11:28:04 AM

That PSU is probably worth about 16A total on 12V rail, regardless of it's label. Remember on lower end PSU it's NOT what they claim it can output, that claimed figure is a peak value it cannot sustain long term.

I have 240W PSU that are better than it is at powering your system. It will not last years and may kill parts when it dies, unless you rarely ever turn the system on and don't do much but leave it idling away.

I'm not saying "more power", I'm saying it isn't even competitive with a good 300W PSU, for example what Dell would spec as 300W is better than it is.

With such a low end PSU you would be better off not having split rails. Cheap PSU (and even some of the better ones) don't have independent 12V rails, they use a low ohm parallel-resistors arrangement which even further reduces the true output. I'm not familiar with that PSU's topology but if you insist on continuing to use it, it could be a good idea to have a fairly high speed fan for it's exhaust wired straight to 12V rail for max RPM/cooling, and (depending on your skill level, don't come back from the grave and complain about being electrocuted) possibly modifying it such that these split rails are recombined into one.
February 1, 2007 7:07:01 PM

Quote:
That PSU is probably worth about 16A total on 12V rail, regardless of it's label. Remember on lower end PSU it's NOT what they claim it can output, that claimed figure is a peak value it cannot sustain long term.

I have 240W PSU that are better than it is at powering your system. It will not last years and may kill parts when it dies, unless you rarely ever turn the system on and don't do much but leave it idling away.

I'm not saying "more power", I'm saying it isn't even competitive with a good 300W PSU, for example what Dell would spec as 300W is better than it is.

With such a low end PSU you would be better off not having split rails. Cheap PSU (and even some of the better ones) don't have independent 12V rails, they use a low ohm parallel-resistors arrangement which even further reduces the true output. I'm not familiar with that PSU's topology but if you insist on continuing to use it, it could be a good idea to have a fairly high speed fan for it's exhaust wired straight to 12V rail for max RPM/cooling, and (depending on your skill level, don't come back from the grave and complain about being electrocuted) possibly modifying it such that these split rails are recombined into one.



I did some investigating based on your comments, and wrote to startech, here is the response I recieved.

Dear George:

Thank you for your inquiry! Our power supplies are manufactured to high
standards and are not cheap power supplies. We use quality components and the
specifications listed in the Technical Specs are what the power supply delivers.

If you have any further questions, please contact us.

Best regards,


Ray Aoki
Technical Support Team
(800)265-1844


Also, I did some searching and found some reviews here:
http://www.techwarelabs.com/reviews/cases/startech_480w...

and here:
http://www.bigbruin.com/html/startech500w.htm

Both reviews and some others say the Startech Psu is quite good.

Did you say all that stuff without really knowing?
February 3, 2007 11:16:01 AM

Quote:
That PSU is probably worth about 16A total on 12V rail, regardless of it's label. Remember on lower end PSU it's NOT what they claim it can output, that claimed figure is a peak value it cannot sustain long term.

I have 240W PSU that are better than it is at powering your system. It will not last years and may kill parts when it dies, unless you rarely ever turn the system on and don't do much but leave it idling away.

I'm not saying "more power", I'm saying it isn't even competitive with a good 300W PSU, for example what Dell would spec as 300W is better than it is.

With such a low end PSU you would be better off not having split rails. Cheap PSU (and even some of the better ones) don't have independent 12V rails, they use a low ohm parallel-resistors arrangement which even further reduces the true output. I'm not familiar with that PSU's topology but if you insist on continuing to use it, it could be a good idea to have a fairly high speed fan for it's exhaust wired straight to 12V rail for max RPM/cooling, and (depending on your skill level, don't come back from the grave and complain about being electrocuted) possibly modifying it such that these split rails are recombined into one.



I did some investigating based on your comments, and wrote to startech, here is the response I recieved.

Dear George:

Thank you for your inquiry! Our power supplies are manufactured to high
standards and are not cheap power supplies. We use quality components and the
specifications listed in the Technical Specs are what the power supply delivers.

If you have any further questions, please contact us.

Best regards,


Ray Aoki
Technical Support Team
(800)265-1844


Also, I did some searching and found some reviews here:
http://www.techwarelabs.com/reviews/cases/startech_480w...

and here:
http://www.bigbruin.com/html/startech500w.htm

Both reviews and some others say the Startech Psu is quite good.

Did you say all that stuff without really knowing?

No, did you really think a company CSR is going to tell you "our products are crap"? You would get that kind of response about the worst PSU on earth.

As for the techware labs article, beware of that kind of non-technical review, they didn't even bother to assess the electronic design nor sufficient load test. I can take any of the lower quality PSU, mate it up with a modest load and run it for a couple hours, but it doesn't tell you anything about it's quality to have it do that. Many poor PSU end up failinglater, even killing equipment but could pass such an inadequate test.

Would you be satisfied with a car, washing machine, or whatever, if it was built worse than the other alternatives? What would having it work for a few hours prove? Nothing really, any product that wasn't defective from the factory would work that long.

As for the second review, are you even aware that is a different PSU? It is a significantly better than the prior, if we consider the better quality generics then the second, Bigbruin reviewed unit might be about average for a 500W, but when you see PSU suggestions appropriate for a system that might need upwards of a 500W PSU, they are not for these merely median grade, average units because they aren't designed for long term use at 500W, that is still a peak, not sustained rating. If I needed a PSu for a modest system and found the one BigBruin reviewed at a low price, I'd consider it. The one in the first review, I would pull out of a system, replace immediately.

Did you notice BigBruin put it up against an ALLIED(!) PSU? Did you recognize Allied are junk? BigBruin apparently didn't, what would be the point of comparing these two? Is it like the PSU special olympics?

On that review we can see that both of them are either miscalibrated (at the factory) or struggling on their 12V rails already, as 12V dips low on multimeter reading while 5V is rising. To be fair they might do better on an older system but you don't want to have to think "use this PSU on a different system" because you buy it for a specific system, normally.

In short, ignore lazy reviews where all they do is hook up to a system and measure voltage then declare it ok. It is a waste of your time, and the reviewer's time. Sometimes a reviewer will show a lot of competence in PSU reviews, but your average reviewer does not, they review like it's just some peripheral that is being benchmarked by the only parameter their layman knowledge can grasp.
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