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GHost117
11-11-06, 01:41 PM
I heard that you need 600-800 watts and that you need 30 amps on a 12v rail. I still dont understand how the rail thing works so I was wondering if any of thse cards would work.

This is a 700 watt card with 4 12v rails at 18 amps each. Will this work or do I need 30 amps on one rail?
http://www.newegg.com/Product/Product.asp?Item=N82E16817341002

There are a lot of simular cards with less and more wattage but i stilll havent found a good one with 30 amps on one rail. As far as i understand if there is more then one rail then the first one if dedicated for the prossesor but the other 3 can pool together for the GPU. Right? If so then this card would work. Right?

Aslo was i right in my information that an 8800 should have about 700 watts?

s3V3n
11-11-06, 01:45 PM
even SLI works on that.

Xion X2
11-11-06, 01:48 PM
Yes, it's overkill for one GTX.

Rytr
11-11-06, 01:54 PM
It should work very well. Have not heard about the 700W. I thought Nvidia recommended a minimum of 450W with combined +12V rails of 30A. Have not checked lately but there were a number of 500-600W PSUs with 30A+ rated rails.
I have a new Antec 480W v2.0 with two 18A +12V rails that I use with my 7950 GX2. This is a solid PSU for under $100.

GHost117
11-11-06, 02:32 PM
Are you sure? I read somewhere that even though Nvidia recomended 450 it really needs about 650 to work well.

Rytr
11-11-06, 02:45 PM
If you planned running SLI then I would say 700W would be a minimum and possibly not enough, depending on the quality of the PSU. But with one GTX I would have no problem with my 480W although I would make it the minimum and would probably go with one of my 600W Enermax PSUs just to be safe.
I was using a 600W with my GX2 until last week and I changed it out with the 480W just to see if any difference was noticeable. The 480W supplies more than enough on that system where the 600W is actually overkill. With all that said, I would rather have more than not enough (especially Amps). :D

noko
11-11-06, 02:49 PM
Running great with 550w single 8800 GTX with OC of cpu. I only think you need a 600w plus if you are going SLI and have alot of other stuff in your system.

|MaguS|
11-11-06, 02:56 PM
Seasonic S12 600w is able to support 8800GTX SLi. ;)

Lfctony
11-11-06, 04:23 PM
Guys I have a Tagan 480w PSU with 28A on the 12V, it should be fine, yes?

nrdstrm
11-11-06, 05:07 PM
Guys I have a Tagan 480w PSU with 28A on the 12V, it should be fine, yes?

Probably not. 8800GTX wants 30 A on the 12 volt :(

Lfctony
11-11-06, 05:25 PM
Well I hope it's ok, I can't afford spending any more money. I spent $880 on that GTX.

Also, I have the X1900XT 512MB now and it's working fine. The 8800GTX requires only 14W more than the 256MB model, mine requires more power than that, since it's 512MB. So it should consume about the same power, given that the X1900XTX consumes more than the 8800GTX.

http://www.techreport.com/reviews/2006q4/geforce-8800/power-load.gif

sillyeagle
11-11-06, 05:33 PM
Well I hope it's ok, I can't afford spending any more money. I spent $880 on that GTX.



Give it a shot. I have not heard of Tagan, but if thats a high quality PSU it might work depending on how conservative the Nvidia recomendation is.

Lfctony
11-11-06, 05:41 PM
I believe they're of very high quality, they cost around the same as the OCZs do in the UK.

Found these at newegg.

http://www.newegg.com/Product/ProductList.asp?DEPA=0&type=&Description=tagan&Submit=ENE&N=0&Ntk=all

Rytr
11-11-06, 07:02 PM
I have always heard Tagan PSUs are quality made. I have never tested one or even used one but people that have them only say good things about their experiences. Think OCZ use re-branded Tagan cores.
If your Tagan has 28A rated +12V rail I would not worry cause the 28A rating is probably conservative. Anyway, you will know if it is lacking because the worse case it will not boot or if it does not have enough Amps it will suffer from instability under load.

GHost117
11-12-06, 12:42 PM
SO just making sure one final time:
if a PSU has 3 12v rails at say 16 amps each then it is just as good as a PSU with 32 amps on 1 12v rail. Right?

If i understand correctly, if there is only 1 12v rail it should be above 30 amps but if there are 2 or more then all but the first rail should add up to 30 amps or more because the first rail will only power the CPU. Right?

I hope so because im buying a PSU in 3 hours or so.

Cyant
11-12-06, 01:01 PM
SO just making sure one final time:
if a PSU has 3 12v rails at say 16 amps each then it is just as good as a PSU with 32 amps on 1 12v rail. Right?

If i understand correctly, if there is only 1 12v rail it should be above 30 amps but if there are 2 or more then all but the first rail should add up to 30 amps or more because the first rail will only power the CPU. Right?

I hope so because im buying a PSU in 3 hours or so.

Yeah thats basicly it, always depending on how thing are distributed on the multiple rails. If the PSU you buy has 3 rails of 16A try to find out wich rail are connected on wich wires.

Usualy rail 1 is the CPU that almost always like that. Then check how are PCI-Express and molex connectors are spread (the manual should have some mention of this if its a good brand anyway). And try split the load (card/fans/hdd) or the remaining rails.

nippyjun
11-14-06, 01:20 AM
Is 36 amps on one 12 volt rail enough for dual 8800gtx's the mobo, and 3 drives? The cpu is on the other 12v rail.

Rytr
11-14-06, 02:23 AM
Is 36 amps on one 12 volt rail enough for dual 8800gtx's the mobo, and 3 drives? The cpu is on the other 12v rail.

Yes.

TiKiMaN1
11-14-06, 03:45 AM
even SLI works on that.

Maybe... Here are the certified PSU's though:

http://www.slizone.com/object/slizone_build_psu.html#certified_powersupplies

glObalist
11-20-06, 07:22 AM
Seasonic S12 600w is able to support 8800GTX SLi. ;)

OK so I read this PSU has 18A + 18A on the two 12v rails. What's the combined output on the 12v then if it can sustain two 8800GTXs?

And is it really true that the CPU takes ALL of the 12v1 amps in dual-rail PSUs, like Xion said in another thread?

I don't think so, as that would leave you with only 18A for your entire system minus the CPU, which would be just crazy...

Xion X2
11-20-06, 10:43 AM
And is it really true that the CPU takes ALL of the 12v1 amps in dual-rail PSUs, like Xion said in another thread?

I don't think so, as that would leave you with only 18A for your entire system minus the CPU, which would be just crazy...

Believe me, it's true. This is the way that all multi-rail PSU's are designed, for the most part (12v1 is CPU only). There are very few exceptions to the rule, like the Silverstone Element 500W and the Mushkin 550W, for example:

Silverstone Element 500W review:
The SilverStone Element 500W is one of the few power supplies we've seen where the two 12V rails are actually additive (18 + 18 = 36.)

http://www.jonnyguru.com/review_details.php?id=23

Mushkin 550W review:
This power supply has a pair of +12V rails, each set to do 20A. The combined 12V capability is 336W, or 28A.

What this typically means is that you can put as much as 20A on each 12V rail, but never more than a total of 28A on both at the same time. But the Mushkin HP-550 has what's called "Rail Fusion." "Rail Fusion" is what Topower calls it when a PSU's rails can be combined to create one big 12V rail.

So obviously the "20A" rating on each rail means nothing. Why even bother with two 12V rails? Well, even though this PSU can not be considered ATX12V compliant since you have rails that are capable of more than 240VA, the rails are capable of isolating EMI from one another. So you do get one of the positive features of split 12V rails while not having to deal with the negative feature of "running out of available power."

http://www.jonnyguru.com/review_details.php?id=31

In most cases, on multi-rail PSU's however, the 12v rails are split up simiilar to the PSU that I now have, the Silverstone Zeus 850W:

The way the 12V rails are distributed are as follows:

12V1: CPU-1. Typically powered through the 4-pin connector of a power supply. On the ST75ZF, power for CPU-1 is provided by the first two 12V wires on the 8-pin EPS+12V connector.
12V2: CPU-2. Typically, dual CPU motherboards that would require each CPU have it's own 12V rail would get it's power from the second two 12V wires on the 8-pin connector. Silverstone also puts the SATA connectors on this rail as well as PCI-e connector #3.
12V3: This rail powers many things. The EPS AUX 6-pin is on this rail, as is all of the Molex connectors (used for hard drives, floppy and optical drives, fans, lights, etc.) and the main ATX connectors (powers fan headers and slot powered cards that require 12V.) PCI-e connector #4 is also on this rail.
12V4: This rail is dedicated for use with PCI-e connector 1 & 2.

http://www.jonnyguru.com/review_details.php?id=15

With the advent of dual and later tri and quad-rail PSU's, PSU companies started dedicating an entire 12v rail to the processor since ATX specs specified until recently no more than 20A on a single 12v rail could be used for multi-rail PSU's. They did this to assure that the system would always be guaranteed to operate at the most basic level. Without doing this, and by stacking other components on a rail with it, they would've been chancing the processor being starved for power since it will generally take more than 20A to run your average system off of, and therefore, the processor would be starved for power in many cases.

glObalist
11-21-06, 12:49 AM
OK thanks for the info, but is Magus' PSU also additive like those Silverstone and Mushkin ones then? Otherwise I don't see how it is pulling all that PLUS another GPU...

Xion X2
11-21-06, 02:12 AM
It's possible, or it's possible that Seasonic seriously underrates their power-supplies.

But yeah, I'd say it's likely the dual-rails on the Seasonic are additive. That makes the most sense.

glObalist
11-21-06, 12:00 PM
Now I cannot get this anywhere confirmed as I'm looking at the Seasonic S12-500 PSU but would anyone know if the rails on it are indeed additive?

I need >30A for my graphics card on the +12v line but if the rails are split then this PSU will not cut it.

Xion X2
11-21-06, 12:32 PM
For your wattage range, you need to just go the safe route with a single 12v rail. The Silverstone ST56ZF is a 560W PSU that has 38A on a single 12v rail and is a great performer.