8800gtx PSU

[dreddfunk]

All though this Christmas season, I've been planning on getting the 8800gts for myself (eVGA). With new information from the wife, I may be able to swing the 8800gtx (which I would love for its performance, though it will apparently be a very tight fit in my Antec Super Lanboy case).

I'm ever so slightly concerned about my PSU, and I'm looking for informed feedback.

I've got the Antec TruePower II 430W, which has two 12v rails, each rated at 17A. My understanding is that means that I have a total of 34A available on the 12v rails, which is more than the 30A recommendation for the 8800gtx.

The PSU doesn't, however, meet the 450W minimum requirement. I've learned enough about PSU's to know that they vary greatly in quality (and thus the reason for some of the minimum 'wattage' requirements).

Yet I wanted to see if the informed readers here at AT felt that the 34A on the 12v rails is good enough (I only have one HD, see sig, but two optical drives), despite having only a 430W PSU (rated for a maximum draw of 410W).

I have read most of the articles on the 8800 series and noted the power draws (which aren't that much more, truthfully, than my x850xt). I'm more just looking for confirmation that I've got the power issue straight.

Thanks!

 

[tersome]

IIRC, you can't just add the two rails. Almost all psus are single-railed, with a chip that splits the current into x amount of rails to be in accordance with some safety spec.

Anyways, 12v x 34A = 408 watts, a nice feat for a psu rated for a maximum draw of 410 watts. Realistically, the psu probably has only 25A or so on the 12v rail, which is well below the 30A recommendation for the 8800gtx. You might be able to pull it off, however.

 

[dreddfunk]

Thanks for the reply tersome, although it provokes more questions. Since the manufacturer's specifications show the rating of each rail, and don't ever provide an aggregate number, how does one determine the total allowable draw on the 12v rail(s)?

 

[SlowSpyder]

I have an Antec NeoPower HE 500 watt (I think that's what it's called). It has 3 12v rails. I think Antec power supplys all have pretty stout 12v rails, but usually are lacking on the 5v power. You have to take the 12v, 5v, and 3.3v into account.

*edit - I looked at some 500 watt power supplies on Newegg. My Antec is rated at 17amp on the 5 volt but other 500 watt power supplies are rated at 30-40+ amp on the 5volt rail. However, Antec seems to put more umph in the 12volt rail then other power supply manufacturers.

 

[Captante]

You might be able to get by with the 430 watt Antec considering how little stuff you have in your system at the moment, there just isn't going to be much to spare & if it blows up un you while in operation it might take other components along with it when it goes including your shiny new GPU.

Its your call, but I'd give serious thought to upgrading to somthing in the 550-600 watt range which will provide a bit more juice then you need now & leave some space for future upgrades.

 

[dreddfunk]

Thanks Slow & Captante, I'll probably just go for the GTS, it only needs 26A and 400W. That's a little bit on the safer side.

There's no way I can convince the wife to spend another $75-100 on a quality 550W PSU in addition to the extra $$ for the GTX. I'll just have to get the GTS from eVGA and start saving for the step-up!

 

[Gamingphreek]

Don't pay any attention to Nvidia's recommendation.

Given what is in your system right now I wouldn't worry about power too much.

Given that in a Dual Core system, with 2 gig of RAM that Anand used in his initial review uses 520 Watt total power in an SLI configuration I would say that you are probably just fine right now. Your problem will come in that you need 2 PCI-E power connectors, I dont know if they make a Y-Splitter for those or not.

Additionally, you can add the power from the two rails. Unless they are completely independent from each other (VERY VERY rare that each rail has independent voltage regulation) you can add them together to get your total amperage rating. I suggest heading over to SPCR. They are EXCELLENT at in depth power supply and electricity analysis.

-Kevin

 

[tersome]

Originally posted by: dreddfunk
Thanks for the reply tersome, although it provokes more questions. Since the manufacturer's specifications show the rating of each rail, and don't ever provide an aggregate number, how does one determine the total allowable draw on the 12v rail(s)?

It should say on the large label on the case of the psu "Max load on 12v rails not to exceed x amps" or something similar. It can be fairly close or pretty far away from the sum of the rails.

 

[dreddfunk]

Thanks again Kevin & tersome -- I found on another forum a common belief that the TPII 430 had a combined 31A on the two 12v rails (though it doesn't say anything like that on the spec sheet or the PSU itself). I did see SPCR's review of the TPII 430, and it was mostly positive, saying that it should have plenty of power for most any configuration.

I don't have a lot of other stuff in my system (and don't plan to) so my gut feeling was that it would probably be fine but I like double-checking with more knowledgeable folks.

Thanks again!

 

[Brian48]

CompUSA has the Antec 550w Trio on sale (ending today) for $69.95 after rebates. This is one hell of deal for this PSU and is much better than it's pricier cousin the NEO.