PSU for 2x5870s

[Net]

background: these cards are used for calculations.

my setup:

i7 980
2x 5850s
850TX corsair

now, i'm adding 2x5870s. I will be using add2psu to allow me to use another psu dedicated to only these 2x5870s.

How much psu do I need for only 2x5870s.

 

[lehtv]

A ~500W unit with four PCIe connectors.

edit: clarification: you will need molex->PCIe adapters to have 4 PCIe connectors on 500w unit. If you don't want to use adapters, buy a unit like XFX 650W that has four PCIe connectors by default.

 

[Smoblikat]

A nice solid 450w to 500w will do fine. It HAS to be a high end one, otherwise you will get low performance due to the other rails not haviong enough load.

 

[Net]

Okay, I just found this on slickdeals: http://slickdeals.net/permadeal/74452/newegg-ecs-ic780ma2-v1.0a-am3-amd-770-atx-amd-motherboard

and I bought it ($15! these are for calculations, x1 PCIe is all I need).

I'm going to run:

Sempron 140
Motherboard ECS IC780M-A2
1GB Ram
2x5870s

How much psu do I need for that?

 

[lehtv]

Since the other components add to the load, I'd recommend 650W. If you were powering ONLY the 5870s you could get away with 500W

 

[Wall Street]

Have fun dremeling those x1 slots open.

 

[Sunny129]

Okay, I just found this on slickdeals: http://slickdeals.net/permadeal/74452/newegg-ecs-ic780ma2-v1.0a-am3-amd-770-atx-amd-motherboard

and I bought it ($15! these are for calculations, x1 PCIe is all I need).

I'm going to run:

Sempron 140
Motherboard ECS IC780M-A2
1GB Ram
2x5870s

How much psu do I need for that?

i'm not sure i follow your logic. you plan on using 2 HD 5870s, which would require 2 PCIe x16 slots just to make them physically fit, regardless of whether you need that much bandwidth or not...and that mobo only has 1 PCIe x16 slot on it. are you planning on butchering the PCIe x1 slots to allow the HD 5870s to fit in them instead?

...which brings me to my next question - what kind of calculations are these cards going to be doing? and are you certain that these cards won't benefit from more PCIe bandwidth (not by speeding up individual calculations of course, but by allowing more calculated results pass through the PCIe bus at any given time)? the reason i ask is b/c i have quite a few GPUs doing nothing but calculations 24/7 in slots w/ full x16 bandwidth, and if i move them to a PCIe x16 slot that's limited to x8 or x4 bandwidth, they don't get nearly as much work done in the same amount of time...

 

[Net]

i'm not sure i follow your logic. you plan on using 2 HD 5870s, which would require 2 PCIe x16 slots just to make them physically fit, regardless of whether you need that much bandwidth or not...and that mobo only has 1 PCIe x16 slot on it. are you planning on butchering the PCIe x1 slots to allow the HD 5870s to fit in them instead?

...which brings me to my next question - what kind of calculations are these cards going to be doing? and are you certain that these cards won't benefit from more PCIe bandwidth (not by speeding up individual calculations of course, but by allowing more calculated results pass through the PCIe bus at any given time)? the reason i ask is b/c i have quite a few GPUs doing nothing but calculations 24/7 in slots w/ full x16 bandwidth, and if i move them to a PCIe x16 slot that's limited to x8 or x4 bandwidth, they don't get nearly as much work done in the same amount of time...

its quite common among the people that do similar work to use a PCIe riser http://www.amazon.com/BestDealUSA-R...ref=sr_1_1?s=pc&ie=UTF8&qid=1334429648&sr=1-1

i'm certain, x1 is more then i need.

Have fun dremeling those x1 slots open.

i'd never do that.

 

[Sunny129]

oh ok...you neglected to mention the riser before, so you had me confused LOL. anyways, good luck w/ your new calculators

 

[Net]

Since the other components add to the load, I'd recommend 650W. If you were powering ONLY the 5870s you could get away with 500W

lets say I add another 5870 so I have 3 5870s total with the sempron 140.

then do I need an 850w, such as a corsair 850 hx? or can I get away with less?

 

[Net]

oh ok...you neglected to mention the riser before, so you had me confused LOL. anyways, good luck w/ your new calculators

That's because they are irrelevant to the question this thread is about.

 

[lehtv]

lets say I add another 5870 so I have 3 5870s total with the sempron 140.

then do I need an 850w, such as a corsair 850 hx? or can I get away with less?

Normally you don't see 850W units with 3x PCIe connectors so you'd need adapters; but a quality 850W unit will handle 3x5870 at stock just fine. E.g. XFX 850W $120 (powerful single +12v rail)