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PSU support for hd 4850 or 4870 crossfire

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January 7, 2010 6:10:18 AM

Hi all

I'm planning to build a new system and was wondering if I could do 2x4850 (512mb or 1gb) or 2x4870 (also 512mb or 1gb) crossfire on this PSU:
http://www.newegg.com/Product/Product.aspx?Item=N82E168...

This PSU has only 2xPCI-e connectors and there's something I'm confused about: the hd 4850 512mb has only 1 connector right? Do these two - hd 4850 1gb and hd 4870 512mb - have 1 or 2 connectors? The 4870 1gb has 2 connectors so I can't run 2 of them on this PSU right?

This has been confusing me forever and I can't seem to find a clear answer searching on google and such. Any help would be much appreciated!

Parts list so far:

(On a 23" 1920x1080 monitor)
http://www.newegg.com/Product/Product.aspx?Item=N82E168...
http://www.newegg.com/Product/Product.aspx?Item=N82E168...
http://www.newegg.com/product/product.aspx?item=N82E168...
http://www.newegg.com/Product/Product.aspx?Item=N82E168...
http://www.newegg.com/Product/Product.aspx?Item=N82E168...
http://www.newegg.com/Product/Product.aspx?Item=N82E168...
http://www.newegg.com/Product/Product.aspx?Item=N82E168...
http://www.newegg.com/Product/Product.aspx?Item=N82E168...


PS: DO you think I could get cheaper ddr3 ram or should I go with at least the one I listed?


Thank you!
January 7, 2010 6:30:32 AM

The video cards will come with molex to PCIe power adapters. It's preferable not to use them, but if your PSU has adequate capacity, you'll be OK.
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January 7, 2010 6:39:09 AM

So you're saying that I could use any pair of the 4 cards with molex (what is this anyway?) if this PSU can handle the wattage? Do you think it can? It does say it is crossfire ready...

Sorry if it's a dumb question I'm obviously not high level tech at all hehe.
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January 7, 2010 6:54:50 AM

The power supply should be fine unless you plan on running a usb farm. Newegg has a PSU calculator on its website, but they way overestimate the power needed...so if you use it subtract about 100w or so from what they suggest.
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January 7, 2010 7:12:12 AM

I just did the calculator thing you mentioned and the results were 657w for 4870 x2 and 579w for 4850 x2. The PSU is labeled 700w but I'm not sure if it can handle the 4870 x2 if I get another HDD for example (696w). Any thoughts?

Another thing... Do you think I should get a better power supply if I want to overclock the phenom II x3 720? (and maybe activate 4th core).

Thanks!
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January 7, 2010 7:54:08 AM

That RAM you suggested is 1600, but my MB says it supports 1333 (it doesnt mention 1600) should I be worried about compatibility?

Btw, can I run a 4850 512mb + a 4850 1gb on crossfire?

Thank you!
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January 7, 2010 8:05:20 AM

Yes, the ram will work fine. If you don't set it manually or OC it will default to the Mb standard settings, but the MB will support it at 1600 OCed.
When you crossfire two cards they will both default to the lowest amount of ram and clock speed (if there is a difference), but will still work together without problems.
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January 7, 2010 2:26:39 PM

That's not a great PSU; it isn't 80+ certified for efficiency. I've read a few things about OCZ PSUs suggesting they may cut some corners on component quality; nothing serious, but there's better out there.
Antec, Corsair, and Seasonic all make some excellent PSUs in the 650W-750W range you'll need for your setup. The Antec Truepower, in particular, are semi-modular and 80+ bronze.
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January 7, 2010 7:03:00 PM

Thanks all for your replies, they were very helpful.

I guess I'm gonna start looking for a slightly better PSU to be safe? Thing is I didn't want to spend too much on a PSU and this one at $50 after rebate seemed like a sweet deal.
If anyone would suggest PSUs for this setup I'd be much apprecciated.
Also any thoughts on 2x PCI-e connectors+molex vs. 4x PCI-e connectors would be very helpful.

I'm still wondering if I could run a 4850 512mb + 4850 1gb setup. Anyone know about that?
If that's not possible, what do you think would be better price/performance wise, 2x 1gb or 2x 512mb? I plan on buying 1 card first and then getting the other one, and I'll be running a 23" at 1920x1080. Due to the high resolution, I thought I would get the 4850 1gb and then add the 4850 512mb (I don't think I need more than that at 1920x1080 do I?).

What do you guys think? Is it a good idea? What would you do?

Thank you!
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January 7, 2010 7:45:38 PM

512 mb is a better deal right now. It will not handicap you in anything but a few titles with AA and AF cranked all the way up. Your overall performance with 2x4850 will be higher than a gtx285, or similar to a 5850. Check out these charts.

http://www.tomshardware.com/charts/gaming-graphics-card...
http://www.tomshardware.com/charts/gaming-graphics-card...

I also disagree about the PSU...I think the one you selected would work well. And to correct a mistake made by the other poster it IS greater than 85% efficient.
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January 7, 2010 9:59:53 PM

The OCZ PSU is NOT 80+ certified. There may be circumstances under which it is efficient, but overall it may not be. OCZ is not a crappy brand, but it is not in the same league as Antec, Corsair, PC Power & Cooling, or Seasonic. I read a couple of articles recently in which they were cited for using some substandard capacitors in their "consumer grade" PSUs. Absent a competent technical review of the model you want, I'd choose something known to be good.
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January 7, 2010 10:57:01 PM

IMO the PSU you currently own is sufficient to power up 2x4850 or 2x4870.

But even if its not(which i highly doubt) you can get the new psu after you've tested the GPUs and witness with your own eyes the lack of power(BSOD, shut downs,unexplained crashes etc)
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January 7, 2010 11:26:00 PM

AFAIK, the Truepower New models are similar, except for the LEDs. They were reviewed very favorably at www.jonnyguru.com.
My next PSU will likely be either a Truepower New or a Seasonic "X;" probably the Antec since I will likely only need 550W.
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January 7, 2010 11:30:40 PM

What about the 4850 1gb vs. 512mb option? is it possible to have one of each on crossfire? Would that be better than a 2x 512mb?
I ask this because I found 1gb cards at only $10-$25 more than the 512mb:
http://www.newegg.com/Product/Product.aspx?Item=N82E168...
http://www.newegg.com/Product/Product.aspx?Item=N82E168...
http://www.newegg.com/Product/Product.aspx?Item=N82E168...

Which of the above would be better btw?

Also which of these 512mb cards is better?
http://www.newegg.com/Product/Product.aspx?Item=N82E168...
http://www.newegg.com/Product/Product.aspx?Item=N82E168...

Sorry if these questions are annoying, but I just can't stop wondering about these options.

Thanks!



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January 8, 2010 2:00:54 AM

Okay, I'll try one more time and then I'll give up. If you've been convinced by jtt that all the specs provided by the PSU you originally posted are just made up, get this http://www.newegg.com/Product/Product.aspx?Item=N82E168... it is the best PSU made under 850W. I have personally used it in 100s of builds without a problem. (it is our gaming PSU of choice unless more power is needed for quad crossfire/sli) Although for your needs it is probably no better than the original model you were looking at.
I've answered this before, but I'll do it again. YOU CAN RUN A 1GB AND 512GB TOGETHER, BUT THEY WILL BOTH DEFAULT TO 512GB WHEN YOU DO. Did you check out the graphics charts I linked for you? You really have nothing to gain by getting the 1gb versions of the cards. I would probably go with the sapphire 512 because it has a vent which will help with cooling. You could acheive the same with the powercolor model by removing the rear expansion cover on your case directly below the slot you use for the card.
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January 8, 2010 2:25:13 AM

I apologize belial2k, in the previous post when you talked about them defaulting I didn't quite get it... all these tech specs are kinda new to me and this will be the 1st system I will build. For that reason I thank you and everyone else for all of your advice. It has helped me much in making informed decisions on how to build this system.

About the PSU, I'm debating if I should (risk it and) go for the OCZ or get another one double the price, but that will give me a little bit more peace of mind.

Guess I will go with the 2x 512mb then, sorry for being a pain!

Tom's forums + Newegg = EPIC WIN!! :D 
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January 8, 2010 2:50:20 AM

No problems....I didn't mean to come off as rude, but it seemed you kept asking the same questions after they had been answered. I build custom computers for a living, so don't often give completely wrong advice, although from time to time us old timers will have a slight difference of opinion on subjects like PSUs and such. This is where I should have pointed you in the first place...it is a very good and accurate PSU calculator unlike the one on newegg that severely overestimates the Power needed....
http://extreme.outervision.com/PSUEngine
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January 8, 2010 4:36:32 AM

Thanks for the link, that's very handy, though I don't know what to put in the "overclocked Vcore" field. I put 3300 for OC'ed Mhz.
And should I add the OC'ed cpu wattage to the wattage up top?

Thanks
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January 8, 2010 5:26:48 AM

just select your cpu from the drop down menu, then in the overclock part select what you WANT to Oc to, in the voltage put 1.45 (probably more than you'll ever use, but this is the max safe voltage on the cpu) then hit the OC button and it will calculate the cpu wattage for that OC....I think the rest is pretty much self explanatory...just select all your components from the drop down menu. When I ran it for your rig I came up with around 450W.
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January 8, 2010 9:01:29 AM

I wasn't looking for an argument. I also wouldn't say the OCZ specs are "made up," just that when buying new, there's better out there, such as the Corsair belial2k linked.
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January 8, 2010 2:51:03 PM

Not trying to argue, and I respect an honest difference of opinion. I don't think the big issue with that PSU is efficiency, though. It has been tested to greater than 85%, so I will believe OCZ until they are proven wrong. What I would worry SOME about is reliability, since reading the reviews about 5 -10% seem to blow up in the first year. It seemed the OP was looking for a "bargain" it seems to have good specs and decent reliability for the price. But if you don't mind spending a little extra cash, the corsair should eliminate all worry. As I said, out of 100s of builds I've never had a customer have an issue with one of those, although I have had a couple arrive DOA (quick replacement from newegg, though)
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January 8, 2010 4:31:24 PM

I have another question about the calculator belial, in the video card field should I put 4850 x2 and then Crossfire for the video type or does this translate into 4x 4850?
I'm still getting around 550w when I calculate that's probably the issue no?
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January 8, 2010 4:42:36 PM

yes, you should just be putting one 4850 in the video card section, then select crossfire in the next dropdown menu.
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January 8, 2010 4:58:21 PM

Thank you all, I think I'm all set to boot! :D 
Your immense help is truly appreciated!
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!