How much power will I need?

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Borna12345

Borna12345

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Croatia
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I've checked across several different PSU calculators, and results are not consistent, so I figure I will ask here:
Intel i5-3550
ASRock Z77 Pro3
AMD Radeon HD 7770 (MSi)(I might get a 2nd one eventually - a lot depends on the PSU)
Seagate Barracuda 7200rpm, 500GB
DVD-RW, CD-RW drive
I've got some telling me I'll need around 400 watts for CrossFire, some saying I'll need 650 watts for two cards... If you could specify some range of wattage to buy, and how much amps I'll need on which output - it'd be much appreciated.
 
I think a psu with about 400w would do the job well for a single card and would give you enough power for you to add some hard drives. Example Corsair CX430

For crossfire you would need more power but I think 500-550w would be good enough because the 7770 is not very power hungry.

Don't take my advice as fact as I am not very experienced.
 
Well Tuga your advice is right on the spot. 400W PSU at least for a HD 7770 and if you want to crossfire, at least a 500W PSU. 80Plus certification ratings are important too. That way you will have an idea that it will perform close to the adverted power ratings.
 
That would be cutting it very fine. I would go with 650 standard and 800+ for crossfire.

It looks like 7770's use a little over 200w each.
 
450-500 watts with 36A or greater is pretty much on the safe side for HD 7770 Crossfire setup.

EDIT: Corsair CX500 should do the trick. It has 38A@12V and 2x PCI-E.

DQuaN
It looks like 7770's use a little over 200w each.
Click to expand...

Two HD 7770's use 160W max total. Where did you get that kind of a number?
 
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I tend to agree with DQuaN. It may also be worth remembering two other general (i.e. not always true) points:
1) a less stressed PSU will live longer, because point 2 means it'll generate less heat and heat is generally what kills capacitors.
2) a PSU is more efficient under lower utilisation, meaning a 650W PSU giving you 390W (for example) will use less current from the mains supply than a 400W PSU giving you the same amount. Higher efficiency means less waste, less waste means less heat, less heat is good! Also higher efficiency means lower electricity bills. It may be a small difference but if you're the type who just leaves your PC on all the time (like many people) the PSU may pay for itself in its life time. Maybe. Please don't quote me on that.
 
I don't leave my PC on all the time, and my room is pretty cold most of the time, I think I could get away with some 550 to 600 watts.
 
Get a Corsair/Seasonic 650w+ unit and enjoy not having to replace it for many many years. I have an overclocked 3570K + GTX670 on a Corsair HX650 and it has plenty of power to spare, I could add a second 670 and still not have any power issues ;)
 
DQ's figure is probably from the ASUS calculator - it lists each card as 200 W. Any more recommendations for the CX500? I happen to be able to acquire one.
 
By the way, could you tell us what website are you using for ordering your power supply? We could look around if there's something good before making final decisions, because not all webstores always sell the same stuff.
 
From my experience, I would not get a PSU smaller than 750w. Inefficiencies set aside, 750+ should give you adequate head room for bigger cards, overclocking, more devices, fans, etc.

Trying to trouble shoot issues that are related to PSU shortcomings will drive you crazy. I would rather have too much power at my disposal than having to trouble shoot crazy issues that may or may not be PSU related.

Of course, given some of the hardware out there, you may need even more power, but for what you are listing now, 750+ should give you a safe margin of available power.
 
I know from experance that a card like a HD 6950 will pull 300watts under FurMark with a hdd, ssd, and a dvd drive plugged in(it makes no use of the cpu whatsoever). Add in a test of Prime95 and that increased to 400watts. So what they recommend is the minimum. A HD 7770 in a PC with other parts will probably take 300-400watts, which is why you should get at least a 400W PSU, as it's headroom. That CX500 is a good option. It should allow you to run two cards in crossfire.
 
djinline
By the way, could you tell us what website are you using for ordering your power supply? We could look around if there's something good before making final decisions, because not all webstores always sell the same stuff.
Click to expand...
I'm not using a online retailer, but the prices are the same and I know the guy so I can't really tell you what's available.
nick09
I know from experance that a card like a HD 6950 will pull 300watts under FurMark with a hdd, ssd, and a dvd drive plugged in(it makes no use of the cpu whatsoever). Add in a test of Prime95 and that increased to 400watts. So what they recommend is the minimum. A HD 7770 in a PC with other parts will probably take 300-400watts, which is why you should get at least a 400W PSU, as it's headroom. That CX500 is a good option. It should allow you to run two cards in crossfire.
Click to expand...
Thank you for the advice - I am probably going with the CX500, at least initially.
 
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Sorry for thread revival, but I need to know can I actually do Crossfire on the mobo mentioned above. It has it listed in features, but only one PCI-E 3.0 16x slot so I think they're trolling me.
 
ASRock Z77 Pro3
Z77%20Pro3(m).jpg


- 1 x PCI Express 3.0 x16 slot (PCIE2: x16 mode)
- 1 x PCI Express 2.0 x16 slot (PCIE3: x4 mode)
- 1 x PCI Express 2.0 x1 slot
- 2 x PCI slots
- Supports AMD Quad CrossFireX™ and CrossFireX™

Looks like the second slot is still an x16, just PCIe 2.0 instead of 3.0. Might not be the highest performance but should still be fine for crossfire.
 
I might be incorrect with this:

PCI-E Gen 3 slots can run at Gen 2 slot speeds so CrossFire will work, but it'll run at PCI-E Gen 2 speeds which means you lose *some* bandwidth but not much to really notice a performance drop.
 

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