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Hi all,

Have just started building a new PC which is going to be a mining rig alongside.

The motherboard has room for 3 5850's, but only bought one so far.
Am going to be running an i5 2500k as well.

What size psu do you recommend? I'm trying to go as cheap as possible but don't want it to fail on me!

Thanks

Anywhere from 850+ should be fine. I would go with a 950 corsair just be safe with the CPU.

I have a rig with 4 5830s OC'd running and a crappy cpu and it runs fine with 850.

Ya I agree id go 850 to 900 that way you've got some headroom, if your really tight on money a 750 probably could run that, don't skimp on brand with your psu...get a corsair, antec, seasonic, ultra, OCZ ....ect

I agree basically with everything thats being said.
I have heard this corsair 750 watt is amazing.
http://www.newegg.com/Product/Product.aspx?Item=N82E16817139016

If you don't get something like this bump it up to 900ish and you'll be fine.

Personally I'd go with the Corsair HX850. May be a little more than you want to spend, but the quality and efficiency are worth it. Check out the review of it on hardwaresecrets.com.

Go for 80plus gold unless you get free electricity.

You have to a little careful about trusting the 80+ ratings, since they are allowed qualify for the various levels (bronze, silver, gold) at an unrealistically low ambient temperature. Many of the gear testing sites such as hardwaresecrets.com run their own efficiency tests at realistic ambient temps, and results can differ significantly. There are some silver rated PSUs that are actually as efficient at normal ambient temps as some gold rated PSUs. And some manufacturers actually choose to rate their PSUs at the efficiency they get at normal ambient temps even though they would qualify for a higher rating at a lower temp. The Thermaltake toughpower xt 775w for example would actually qualify for a silver rating, but Thermaltake chose to rate it at bronze instead since the bronze rating more accurately reflects the actual efficiency of the unit at normal ambient temps.

Each 5850 can draw up to 180~200W overclock, so you're looking at 600W + some for the system.
General rule of thumb, don't load a PSU constantly above 80%, maximum efficiency is usually around the 50~70% range.
Going by those limits, you're looking at 850W on the low side and 1300W on the high/safe side.
Anything in between should be OK.

Importantly, go for one with as high efficiency as you can, the amount of power drawn by mining makes the difference worthwhile.

How does this one look?

http://www.amazon.co.uk/Corsair-CMPSU-800GUK-Gaming-Performance-Supply/dp/B004WDY9OO/ref=sr_1_2?s=computers&ie=UTF8&qid=1311887194&sr=1-2

How worth it is it to overclock the gpu's? What difference does it make in terms of m/hash rate?
Thanks for the advice everyone!

Look at the review on Jonnyguru and Hardocp. They test at 50C, which is unrealistically high. PSUs like the Ax1200 and the HCP1200 still maintain their 80plus gold certification.

Depends on your GPU, it would be best if you got a cheap wattmeter to measure your power draw. To optimize returns, clock them up until you start getting less MH per watt than the previous clockspeed.

Anything above 900 watts is extreme overkill if you go with a good brand.

Wow. Literally every suggestion in here has been wrong. 900watts for 3x 5850s? lolz. Only run your PSU at 50%?  ::)

Here's a real rule of thumb: Get a quality PSU and run it up to 100% of its rated continuous power output.

I heard a really good anecdote once -- Buying a cheap PSU is like buying a cheap condom. Seems fine until you have a blow out.

For a mining rig, a quality gold rated PSU will literally pay for itself over say, a decent bronze rated psu, if running 24/7.

I've become a bit of a fanboy of the seasonic X series, though they're not as cheap as they once were. You will likely be fine with an x650, though if you're super super paranoid you can go with say an AX750, such quality it is (and basically the same unit as the X750 with some minor alterations). Also sweet but too expensive is the NZXT Hale90, but looks awesome. Lower quality but still respectable units are the OCZ ZX series, Thermaltake ToughPower, FSP Aurum series, Enermax Pro87+ series, Lepa GXXX series. Not as good units but if you can find a bargain they'll generally be good enough. I'm currently running 2x5870s and 1x5850 on my seasonic X650 right now, as I recall it pulls something like 580Watts from the wall, full load overclocked. That's roughly 500Watts to the system, don't listen to anyone that tells you a 5850 is going to pull 200Watts from the PSU.

A quality powersupply labelled "XXX Watts" can deliver XXX Watts to the system. Which means it can pull XXX + XXX*efficiency watts from the wall, and deliver it all day long 24/7. Now if you cheap out and get some no name cheapo-brand 10000 watt PSU, you might get enough watts, you might not, it might blow and with no OCP destroy your whole rig, or it might not, no one knows. I prefer to play it safe myself.

EDIT: P.S. Corsair makes some very good units, but the GS series is basically their lowest quality, crappest piles of nonsense. Not recommended.

After what he said I'd like to recommend this again http://www.newegg.com/Product/Product.aspx?Item=N82E16817139016
:P

Nobody in this thread suggested "only run your PSU at 50%".


You're going to take responsibility if somebody's quality PSU blows in a few weeks and maybe take out a component or two? Giving the max isn't the same as giving responsible advice. We told the OP the various factors, outline the min/max scenarios so that he can make his decision how fine he wants to cut it or how safe he'd prefer to play it. Giving an unqualified "get a quality psu and run it up to 100% rated" isn't responsible. You're overlooking factors like thermal derating and manufacturing variance.


What you pull is only applicable to your rig. We don't know how exactly he's going to run it, how overclocked, how much overvolting. Again, it's a question of irresponsible and responsible advice.

Using your condom example it's like saying "I can reuse the same condom a few times and never caught anything so just do that". Sure the same condom would probably last a couple of fucks, but who's going to be responsible if somebody follows that advice, get a break and get a STD?



It's XXX / efficiency watts from the wall, not XXX + XXX * efficiency.

OCP doesn't stop a PSU failure from taking out components, it depends on the actual failure mode. Having deployed literally thousands of systems with quality PSU from various manufacturer including Seasonic in one of my previous jobs, I can tell you it's 100% that a good PSU with all the protection mechanism can avoid collateral damage. Just like not every cheapo PSU will cause component damage if it pops.


I'm not saying he can't try to run 3x5850 on a 650W, it's definitely theoretically possible. But just don't make it sound like it's a guaranteed sure no problem configuration.

Hi,

Your advice has been great, have decided I'm going to play it safe and get a top end 850w corsair.

Does this one meet the requirement or is there anything fundamentally wrong with it!?

http://www.amazon.co.uk/Corsair-CMPSU-850HX-Professional-Power-Supply/dp/tech-data/B002FJ6954/ref=de_a_smtd

Cheers!

That one's OK. But if you don't have any objections to other brands or other etailers, how about this
http://www.scan.co.uk/products/850w-antec-high-current-pro-80plus-gold-135mm-quiet-fan-atx12v-23-eps12v-v291-psu

It's 80+ gold for only 6 pounds more?

Long long post. I don't really want to address every point. I already stated that one can go with a 750 if one feels the need to play it safe. What I said was that suggesting a 900 watt PSU was retarded. There is absolutely no way to draw anywhere near that level of power with 3x5850s, unless maybe you have a full time DICE cooling a super high level OC. Suggesting that someone throw money away for no reason is not really good advice. If you've deployed literally thousands of systems, one would expect you to know that. Are you going to take responsibility for someone throwing money into the gutter? Stupid question.


Anyway, for the OP: The Corsair HX850 is a decent PSU, but it is a rather older platform. Someone overpriced for the quality of the unit. I would recommend http://www.amazon.co.uk/Corsair-CMPSU-750AXUK-Professional-Power-Supply/dp/B003QP417E/ref=sr_1_1?s=computers&ie=UTF8&qid=1312195693&sr=1-1 over the HX850 hugely. Not only is it cheaper, and more than you will ever need powerwise, it is one of the highest quality units you can buy and Gold Rated (I believe it tested something like 89% efficient at full load).

Again, don't listen to the naysayers, a 5870 uses far more power than a a 5850, I've run overclocked as hard as the cards would allow 4x5870s on a Hale90 850Watt PSU, with room to spare (Wall draw was 901Watts overclocked, even assuming an 87% efficiency that's 783Watts).

While I agree fully that there's no way for 3x5850 to draw up to 900W, saying it's retarded is not true.

I guess the problem here is that we have very different definition of safe. Your definition of safe includes running a PSU at 100% load 24/7 and "paranoid safe" is just running at 80% load. For some of us, "safe" includes margins for thermal derate, degradation from deterioration over time and safety margins for load spikes. While 3% different in efficiency might seem insignificant, but when you're running high power 24/7, 3% will add up to a lot. In some places, that would pay for the difference between a 750W and a 900W in less than 12 months. That is the difference between running a PSU at 50% and at 80~100%.


You see the difference is that you are telling them to do something risky without any caveats, in a way that makes it sound like your recommendation is the only way.

I take full responsibility for my comment because I lay out the lower and higher bound, stating why (general safety and optimal efficiency) and leave the decision of which way to go to the person. I didn't tell him "The rest of them are all idiots, just buy a 1200W, or a 1000W if you're a cheapskate!" ;)

Are you on drugs???

Use calc http://extreme.outervision.com/psucalculatorlite.jsp

Input CPU and Video Cards only, recommended is what your will need 12v.

Using HD 5870 shows 570 watts are needed for three.

Recommended that 12v output on PSU label closely matches model number and what calc. gave needed.

Open air or case with PSU in the bottom are best for mining.

GOLD rating will probably not pay off and SILVER will only pay off if you get a great deal.

Can usually gauge a power supply by warranties ie. one , three <==minimum, five, or seven years.

http://www.newegg.com/Product/Product.aspx?Item=N82E16817703027

http://www.newegg.com/Product/Product.aspx?Item=N82E16817341049

http://www.newegg.com/Product/Product.aspx?Item=N82E16817371031 (they had these for $40)

Newegg is high priced unless there is a sale, sometimes higher rated psu is cheaper, and watch the shipping.

There are other stores on the web you know a google, bing search, buy.com, walmart.com,

amazon.com can be used for shopping.

And not enough PCIe power use Molex => PCIe Power Adapters included in card boxes.

No, are you?


Alright, fair enough. although the riskiness of what I am suggesting is still overblown a bit. I have both calculated and empirical data on the general usage of a normal mining rig utilizing what he requested. I gave specific examples of exact make and model PSUs that are well known to be overdesigned to ensure clean and stable power at and above their rated power levels. Even after a few years (the general time-frame where the largest amount of degradation occurs) of relatively intensive usage, the bare specs, and "safe" suggestion will be fine. Now admittedly I didn't layout the case where the OP runs a full water loop with chiller in reservoir and extreme overvolts to murder gpus as fast as humanly possible, but I expect that in that case they might mention something like that. If not, well, caveat emptor, I don't live to warn everyone of every contingency life might possibly envision. Two standard deviations is enough for me.


although that is probably the best PSU calculator around, it is still flawed, and I wouldn't really use it to gauge my needs. I also disagree with your statement that gold rating will not pay off. Here is a simple example:

Say you have 3 PSUs, one is Gold, one is Silver, one is Bronze. Since we're building a beefy system lets say that they're running at 50% load for a 850Watt PSU, or drawing 425Watts.

The draw from the wall for each is --
Gold: 472.22Watts
Silver: 482.95Watts (+10.73Watts from gold)
Bronze: 500Watts (+27.78Watts from gold)

Over the course of 1 year, running a 24/7 mining load, assuming 11¢/kWh that turns out to be $26.77 difference between gold and bronze. Higher loads yield even higher savings (double the load is a little more than double the savings). Unless you don't plan on using the PSU very long, or your power is very very cheap, or you find a very cheap bargain PSU, gold rated PSUs will pay for themselves in savings over a bronze rated one most often in mining.

I would recommend a Corsair 850 PSU.  I am running 3 HD5850's and an HD5870 on my Corsair 850 without any problems at all.  Its a very solid PSU.

Amazon has them for about 134 bucks!  Heres a link:  http://amzn.to/o0VCiO

Just buy a quality brand with a warranty (design life) for the time frame you will be using it.
A quality brand will output it's fully rated power safely and shutdown safely when overloaded.
Was dead on for my setup Intel i5-2500k and two hd 6950s @ 510 watts AC individual results may vary. Bronze 750w $70 Gold 750w $140; Considering most of that $26.77 will be heating your house in the Winter and power rate is cheaper the more power consumed it is going to be a long time to close that gap. $70 / $13 = 5.4 years at best.

Indianapolis Power & Light Company
One Monument Circle
Indianapolis, Indiana

Customer Charge
For bills of 0-325 KWH per month
$ 6.70 per month
For bills over 325 KWH per month
$11.00 per month

Energy Charge
Any part of the first 500 KWH per month
6.70c net per KWH
Over 500 KWH per month
4.40c net per KWH
With electric heating and/or water heating
over 1000 KWH per month
3.18c net per KWH <==========This is what you save not 11c

Must be nice where it's cheaper to use more power. Sadly, some of us pay more as we move up the usage tier. :(

Is it the same throughout the US like where ever bitmofo and bcpokey are (making the assumption they are Americans), or just Indianapolis?

Agreed, go gold and 1000-1200W range, you want optimal efficiency, which is around 50% load. Gold tends to last better, get better RMA service as well.

Also buy a spare PSU for all your rig, be safe and minimize downtime.