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Will a 650w run 2 crossfire 6950s?

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September 30, 2011 10:44:13 PM

My Current Rig:
1x MSI 87A-G54 AM3 Motherboard
1x AMD Phenom II x4 955 (Not Overclocked)
2x 2GB of XMS3 RAM @ 1333MHz
1x 320GB LAPTOP HDD as BOOT DRIVE
1x 1TB DESKTOP HDD (for files and FRAPS)
1x Standard, Crappy DVD Drive
5x PC FANS of Mixed Variety & Sizes
1x ATI Radeon HD 5770 (Not Overclocked)
**ALL OF THIS IS RUNNING ON A 650w PSU**

I Plan To Upgrade To:
1x Phenom II x6 1100T (Overclocked To 4.0GHz)
1x Corsair h80 Water Cooling System
2x ATI Radeon HD 6950 (Also planning on Unlocking those to be 6970s)
2x 4GB of XMS3 RAM @ 1333MHz

My current rig is quite amazing compared to what I used to have to deal with but its coming to the one year mark and the only thing i've added from the original build is a hard drive, a new case, and a Black Magic Intensity Pro. I mostly play games and live stream xbox but with the release of BF3 I really want to play it on Max settings and get more into Eyefinity gaming. I've picked my parts and thats definitely what im going with but the problem is that I am not sure if my PSU can handle it all. I can always go without overclocking the CPU/CARDS to save some wiggle room for the other things and I really want to avoid buying another power supple as those are really expensive. Could I risk putting this all together, firing it up, and the powersupply not working?
October 1, 2011 8:55:27 AM

Ok so i've pretty much come to the conclusion that yes, a 650w will be just fine :) 
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a b ) Power supply
October 1, 2011 9:06:19 AM

It also depends on the quality of the psu. A good silver/gold efficiency power supply will pose no problem, but an average bronze quality one can be troublesome.
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October 1, 2011 9:10:41 AM

gaming wise where do you see the point of changing your cpu from 955 to an 1100T?
The difference is minimal at best...why dont you just get a cpu cooler for the 955 and overclock that to 4.0ghz?

Also since you have an AM3+ board... it would be foolish in my opnion on buying the 1100T now... wait for bulldozer to come out before you upgrade your cpu since it will be compatible and a totally new architechture with better performance...

Also I don't think you will be able to run two 6950s on a 650 watt psu, at least not reliably since you will be at a very high load on it. What is the exact brand and model of your psu?

Use this PSU calculator http://extreme.outervision.com/PSUEngine, select your components, and remember if you plan on unlocking to 6970s select those since they use more power.
The conclusion is you will need a bigger power supply.

My recommendation is to for now get a single 6950, see how it goes, and then wait for the bulldozer chips to be released and buy one of those instead of the 1100t.
Also don't upgrade to 1333mhz ram, get at least 1600mhz since the price difference is so small anyways/
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a c 87 ) Power supply
October 1, 2011 5:20:21 PM

circumventor said:
Ok so i've pretty much come to the conclusion that yes, a 650w will be just fine :) 

Yes you are correct.
I agree with some of the point Amirp makes. Mostly about the CPU. But he is wrong about a 650W unit not being able to power two a build with two 6950s.
Altho as others have said it depends on the quality of the power supply. What make and model do you have? Or otherwise reassure us that it is high quality.

ksampanna said:
It also depends on the quality of the psu. A good silver/gold efficiency power supply will pose no problem, but an average bronze quality one can be troublesome.

It seems like you misunderstand efficiency. It doesn't effect how much power the unit is able to supply, it effects how much power is drawn from the wall to supply the power that the unit is actually using.
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October 1, 2011 5:47:23 PM

Yeah it's not the efficiency of the power supply like ksampanna said, but how many amps it offers on the 12v rail. The higher the efficiency the less power it needs from the wall to supply the same amount of power, so regardless of the efficiency rating (bronze, silver etc.) it still can provide the power required assuming it's a quality unit.

Silvune the only reason I say it wont power it is because personally I wouldn't stress a power supply so far, at 100% it can't really be all that efficient can it?
Also take a look at how many fans he has, and the fact that he wants to overclock cpu, and unlock the gpus, and add in a watercooling system. Would that not add a decent amount to the power requirements?
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October 1, 2011 8:10:49 PM

My power supply is an ULTRA ULT-LSP650P.

I know about the bulldozer chips but there is no release date on those am I correct? If they are coming out soon then ill spring for one of those since my board is AM3+? I couldn't find anything on MSIs website about whether or not I could run an AM3+ chip but if you say so then thats awesome. I need the processing power because I livestream xbox and PC and my current processor has issues with some games (BF3).

As for overclocking my current one, I've cranked it up to 4.1 GHz just for encoding video and then I drop it down to 3.5GHz just for everyday use. Im using the stock fan and im getting around 70c full load. Is that bad? I've got some spare cash right now I could also run over to COMPUSA and pick up some form of cooling unit.

Probably just wait a month or two before I do any of this actually because of the FX chipset and all that. I would like some pricing information before I purchase anything :) 
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October 1, 2011 8:26:55 PM

here's the bad news:
You definitely CANNOT I repeat CANNOT run that system on that power supply. Doing so would be dangerous and foolish. Sorry for being harsh but that is an awful unit, no certification, and low 12 amp rating. Those tigerdirect Ultra power supplies aren't very good. Buy a new corsair or other QUALITY brand power supply with at least 750 watts for dual 6950s and your other desired components.

for example your 650 watt power supply only has 38 amps on 12v rail.
My corsair 650 watt power supply has 53 amps on 12 v rail.... that is a huge difference meaning mine can supply much more power than yours.

Lesson: dont buy cheap power supplies.
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October 1, 2011 11:03:23 PM

Ok thanks. That is what I needed to know.
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October 1, 2011 11:12:28 PM

And btw sorry I forgot to answer your previous questions,
I am not extremely informed, but I see AM3+ on your board so hopefully bulldozer will be compatible in the future. EDIT: I am only saying AM3+ because you wrote it up there, where did you see this? I checked newegg and it just says AM3 for that board.

And 70degrees is too hot for sure. According to AMD max temp should be 62 degrees: http://products.amd.com/en-us/DesktopCPUDetail.aspx?id=...
Im sure you will be reducing the lifespan of the cpu at those temperatures.


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October 2, 2011 5:06:24 AM

ah, I didn't mean to put AM3+. Going to edit my post to avoid further confusion :) 
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a b ) Power supply
October 2, 2011 5:23:01 AM

Sadly, 6950 crossfire will likely get a nasty bottleneck from Phenom II @ stock clocks (even overclocked) in most situations.

Bulldozer could be different however. Especially if you decide to overclock.
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October 2, 2011 5:39:32 AM

circumventor said:
ah, I didn't mean to put AM3+. Going to edit my post to avoid further confusion :) 



On the msi website there seems to be two versions, and one it says AM3+ , maybe a bios update will let you support AM3+ CPUs, definitely look into it in the future if you decide to go for bulldozer chips.

Also something I just noticed.... your board only supports 16x and 4x crossfire... meaning your second card willl be bottlenecked by the pci-e slot. Honestly I wouldn't recommend doing crossfire with two 6950s on a board like this, esp with a phenom II x4.

You're good to buy one 6950 though now, and then save up for a new system if it's not fast enough still.
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October 6, 2011 12:38:43 AM

Good deal. Ill probably go for a top-of-the-line motherboard, and PSU when the 990FX comes out.
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October 6, 2011 12:57:45 AM

Or, could I use the 990FX in my board now, purchase a higher end card like the 6990, get a 1050w 80+ Silver rated psu, and skip Crossfire all together? I could always go for this that way ive got the latest and greatest CPU, GPU, and I wouldn't break the bank as much as throwing out my entire rig save hard drives and ram and starting from scratch. I could always buy a new mobo later :) 
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