# saphhire 6870+PSU



## reflexx20 (May 16, 2011)

is FSP SAGA 500W ok fr 6870 or 6850 toxic edition??.......budget is 2k..


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## Piyush (May 16, 2011)

what is your full setup?
please do mention the processor , amount of RAM, HDD and any other device necessary


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## reflexx20 (May 17, 2011)

@piyush Gigabyte G-41 MES2L v1.0
            E5200 @ 2.8 GHz
            3 GB DDR2 800 MHz
            No system fan...:O
            seagte barracuda 500GB
            and planning to buy 6870 + FSP SAGA..


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## Piyush (May 17, 2011)

for 6850 its enough
but 6870 ....its a so-so situation
better to go for these

tagan stonerock 500W @ 3k
corsair vx 450W @ 3.5k


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## sukesh1090 (May 17, 2011)

^^i think he has overclocked his processor,so 450 will it be enough for him?


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## Piyush (May 17, 2011)

hmmm....by 300mhz i guess....
both of the above PSUs i mentioned will do good job


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## Cilus (May 17, 2011)

I think a 500W PSU is necessary for the build. SO better go with the TAgan Stonerock 500W 80+ Bronze


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## coderunknown (May 17, 2011)

when he is spending 10-13k on a GPU, why not spend that 1k & be safe. FSP Saga II will handle but peace of mind not guaranteed


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## reflexx20 (May 18, 2011)

hmmm....lets see....thanxx all fr ur suggestions

wat abt corsair CX 430 @ 2.2k  for 6850 toxic edition or 6870???


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## Piyush (May 18, 2011)

first of all, finalize your gfx card
6850 and 6870 are 2 different deals
so finalize gfx card first and tell us your decision


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## reflexx20 (May 18, 2011)

@ piyush bro if corsair CX 430 can handle 6870 den i'll go wid dat


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## coderunknown (May 18, 2011)

CX430W is a bad choice. either get CX400W or tagan 500W @ 2.8/3k.


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## saswat23 (May 18, 2011)

BTW whats your total budget. I mean how much at max can you spend..???

Avoid CX-430, as SAGAII 500W is much better than it. Instead go with CX-400 with 400 bucks more.


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## reflexx20 (May 19, 2011)

@saswat23 11k fr GPU + 2.2 k fr PSU....:O......overall 13k (approx)


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## Piyush (May 19, 2011)

then it should be 6870 with FSP saga 500W


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## reflexx20 (May 19, 2011)

@ piyush so are u sure that there will be no problems with FSP SAGA 500 + 6870 ........i'm just asking to have a peace of mind..

because i want know that whether SAGA provides just enough power or more than enough power to meet 6870's requirements......


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## Cilus (May 19, 2011)

FSP SAGA 500W can handle HD 6870 and in your situation it is perfectly ok as your system components are not the power hungry ones. The major advantage of all the new AMD cards are the low power requirement. HD 6870 consumes even less power  than GTX 460 1 GB version. So it is safe to go for a FSP SAGA II 500 along with HD 6870.


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## reflexx20 (May 19, 2011)

one more question Cilus...

what's the difference between dual rails of +12V providing 18 AMP each(in total 36 AMPS)

and a single rail of +12V providing 35 AMP.......and if both provide almost same AMPS  then y the single rail PSU are expensive????


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## Cilus (May 19, 2011)

Actually most people think that the 12V rail is required for supplying power to the Graphics card which is actually not true. Actually the 12V rail delivers the current to most of the components and also minimize the current loss
Computer peripherals like CPU, mobo needs high amount current in low Voltage. Normally the dencer components like CPU, GPU need low voltage power.
 Now you guys know that 
I= V / R and P= V X I
I=Current flowing to the circuit
V=Potential difference 
R= Resistance of the circuit.
P= Power

Now if you reduce V then for supplying same amount of power, I needs to be increased.

Initially the 5 V rail was used to supply the 50-60% current to the circuit but that leads to high power loss as for  maintaining low voltage with high amount current, the resistance needs to be increased which leads to significant power loss. For minimizing this power loss the concept of 12V rail has came to the picture. A good PSU should deliver its 85 to 90% power through its 12V rail and the power output in 12V rail is more important than the total power output.

Now if a single 12V rail is used to deliver the 85-90% power of the total power then this wires need to be of very very high quality with minimal resistance for suppressing heat generation, power loss and most importantly damage to the wire. Thats why some of the PSU use multiple 12V rail.

Typically, a power supply will guarantee at least 17 A at 12 V by having a current limit of 18.5 A, plus or minus 8%. Thus, it is guaranteed to supply at least 17 A, and guaranteed to cut off before 20 A.
These groups are the so-called "multiple power supply rails". They are not fully independent; they are all connected to a single high-current 12 V source inside the power supply, but have separate current limit circuitry. The current limit groups are documented so the user can avoid placing too many high-current loads in the same group. Here the total power that can be delivered through the 12V rails are not specific to individual rails but actually to assigned to the whole group.

But most of the premium PSU makers actually use single 12V rail to omit the extra complexity and circuit limit circuitry. They actually use very very high quality components to deliver the whole power through the single 12V rail.

So dual 12V rail with 18A each does not mean that it can provide (2X18 X 12) = 432W power. It can only provide the amount of power that has been specified by the manufacturer to the whole group. So if a PSU has two 12V rail with 17A each and the total 12V rail has a rating of 350W then each of the wires limit is also 350VA, not 408VA.
Although dual or multiple 12V rails look more promising than their single rail counterpart, there are some problems. It is because assignment of connectors to rails is done at manufacturing time, and it is not always possible to move a given load to a different rail.


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## reflexx20 (May 20, 2011)

@ cilus wow !!! that was great......thanxx


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