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New member help (psu related)

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Adonai

New Member
Joined
Sep 24, 2012
My Specs (for reference):
AMD Phenom II X4 965
RAM: 8GB (2x4GB) DDR3 PC3 [email protected]
Motherboard: Biostar TA790GX A3+
GPU: Radeon HD 5770
HDD(s): 2xSATA [email protected]
Power Supply: Antec Earthwatts 650 (EA650)

Hi,
I'm a new member to the community. Actually, I think I had an account on this forum once a while back, but it's been so long (over a year) I went ahead and signed up a second time. I've been considering an upgrade for my system, well more like two upgrades, but one of the upgrades I'm considering involves a potential power supply and since I don't know much about performance psu's (still learning) I've come to you for all advice. I've got a bit to explain, but if someone could be kind enough to read what may unintentionally turn out to be a lengthy post and help me out I would greatly appreciate it. So I've come to a point where I've decided to try out crossfire. Not that anything is wrong with my 5770 which has been a faithful card for about three years now, but it is starting to show its age performance wise. I'm getting slight framerate lag in games, nothing major and they're not even half a second, but instead of spending a lot of money on a Radeon HD 7000 series card I would go crossfire instead and get relatively the same performance. When contemplating crossfire there are two major factors to consider which are motherboard and power supply.
I've looked into my motherboard and it can handle it. It runs a single PCI-E 2.0 gpu at x16 but will only do multi-gpu at x8. I'm losing half of the bi-directional bandwidth on the pci-e bus, but I figure it's a trade off since with two gpu's I'll be able to run most newer games at max settings. Now, comes the power supply.Since with AMD/ATI it doesn't matter what two cards you can crossfire and they can be from any series I'm looking to add either a 6870 or a 6950. I'm not sure which it will be yet, it all depends on which I can get for a better price so it will be one of those two and I'm just biding my time on ebay waiting for the best deal.
I really don't want to spend more money on another psu if it isn't absolutely necessary so I went to a psu calculator to get a general idea of what I would need. My Antec EA650 has been a great psu and running strong for about five years now. I really haven't had an issue with it yet and being an 80+ certified it is relatively inexpensive to run. I think it was a good buy and I like it, but I'm not sure if it can handle crossfire. I put in the specs of what my system would be with an additional gpu and the recommended wattage it gave me was 573 w. On the same webpage as the calculator it stated one of the most important aspects to consider is the total amperage of the +12V rails. I wasn't exactly sure of what the EA650 had, I know it has three +12V rails, so I went onto newegg and looked it up. The EA650 has the output listed as: [email protected], [email protected], [email protected], [email protected], [email protected], [email protected], [email protected]. It also has 1x6 pin and 1x6+2 pin PCI-E connectors. From the way it looks it's designed to be a power saver and it's questionable if it can handle a performance setup as efficiently and maintain system stability. Now newegg has the EA650 listed as SLi certified and crossfire ready, but when I click on the details tab in the sections where it says SLi certified and crossfire ready it specifically says "No" for both. The dicrepancy is a typo, but since it exists it makes me question my psu. Either it can handle crossfire or it can't and I'm not sure which now.
So looking at psu I've narrowed my selection to a Corsair Enthusiast series CMPSU-850TX which is about $110 on ebay. At 850w it can undoubtedly handle the power requirements and its output is listed as: [email protected], +5V30A, [email protected], [email protected], [email protected] The corsair seems to have only one major +12V rail at 70 amps, but it has four PCI-E connectors (2x6 pin and 2x6+2 pin). I'm also beginning to wonder if the corsair's second +12V rail really is 0.8A...that seems kinda low. I can get other 850w crossfire psu's on ebay such as Vioteks (in the $60 price range) and Azzas (in the $70-80 price range), but these units are highly questionable in quality and reliability. I get the impression Corsairs are pretty well known and well liked units from what I have read on these forums as well as the net so if I'm going to spend some money might as well as shell out the extra $40+ and get something with a reputation. Of course if I can avoid spending money on another psu altogether then that would be preferable. So, what do you all think? Bite the bullet and try a crossfire with my Antec or make a grab on the Corsair? I really do apologize for such a long post, I probably could have shortened it a bit, but I wouldn't to provide as much relevant info as possible so that I can get the best recommendation. I want the Corsair, but I don't know if I really need it.
 

Bobnova

Senior Member
Joined
May 10, 2009
Hi,
First up, AMD is more friendly with pairing cards than Nvidia does, but they still have to be very similar.
A 5770 can crossfire with a 5770 or a 5750, but that's it.
The first two digits have to match. A 4870 for instance can crossfire with a 4830, 4860, 4870 or 4890. A 7770 could crossfire with a 7770 or a 7750.

Your current EA650 PSU is more than enough for a second 5770. It's good enough for almost any two AMD cards when you get down to it.

The corsair's -12v is just that, negative 12 volts. It's used for ethernet and/or serial ports I think. Not much uses it other than for signaling.
 
OP
A

Adonai

New Member
Joined
Sep 24, 2012
Thank you very much for your response. You pretty much told me what I wanted to know.