Topic: PSU question: Is 850W enough for 3 cards?? (Read 1702 times)

that rad is good for 1.2kw at 10c delta with 9 low speed 120mm fans the rad is a mo-ra 1080 i think

milk crate rigs get to hot because of room temp ( my rigs are staked to draw air from the house and blow hot air out the windows lol )

i think the 120mm fans are 1.2w each lol

if you need more info or have questions pm me

zack

You have basically what I have for my main machine.  I have a 1055t overclocked ( no water cooling....lol) with ssd as boot drive, and 8gb. My main minning rig is using semperon on a ASROCK|970 EXTREME4 AM3+ 970 R. And a 1000 gold 80 plus power supply.

that rig is a 1090t cpu 256gb ssd cpu watercooling ( 25w waterpump ) 6 120mm fans  8gb ddr3 1600and a led  monator lol have a look at it its my card testing rig / gaming rig lol
http://s1315.photobucket.com/user/zackclark70/library/#/user/zackclark70/library/

edit its a hx750 psu so max it can pull from the wall 850w ( at 90% efficiency )

edit croshair iv motherboard

Properly undervolted 7950 (I run mine at 1.075v that gives me 630kH) draws just under 200Wa. Your system is using between 100-160wa.

In one of my systems I run 3x5850 and at the wall I have 500 wa consumption.

You should be able to run comfortably 3x 7950/7970 or 4 older cards at efficient PSU utilization.

Kill-A-Watt is awesome tool when optimizing your miner settings. Remember, you want to undervolt and overclock your GPUs.

 

Thanks for the pictures. Nice rig, I like your fan setup.
My 3x 7950 system is a milk crate setup with a single 20 inch box fan blowing across it. The box fan uses 80 Watts even on the lowest setting. I'm thinking of moving to a 3x 120mm fan setup like yours to save some Watts.

That radiator for your CPU is insane! Its like something off a motorcycle or small car! I like it.

Now, if only I could work my way up to 20 rigs like you.

Damn...I am running my 7950s (650khs) at:

1120 core
1550 memory
15% powertune
19 intensity
16334 threads.


Also got a 6870 cranked up to 415khs. (Special 6870 card...5870 rebranded)
https://bitcointalksearch.org/topic/rebranded-5870-6870-for-only-130-on-newegg-200060


Looks like I am burning some juice...  

I might try to under clock/volt to see what type of savings I can get.  You guys have yours really dialed in for power savings!  

im using reaper so mem clocks dont make much difrents  1250 is the standard seting on my cards
it makes 4w difrents lowering the mem to 1000 on the 7950 vaporx oc edition but makes them less stable and gets 10kh less

( i have 20 rigs with 4 cards and 1 test rig with 3 cards )

picks of my test rig its only cpu watercooled because i game on that rig ( amd 1090t ) http://s1315.photobucket.com/user/zackclark70/library/

Thanks for the kind words. 

The Asus power supply calculator that you linked is nice but it provides very high estimates. This is not an entirely bad thing because of course, as you pointed out, power supplies are typically most efficient around 50% load and it's always better to have a larger power supply than you need.

My motherboard and CPU are quite efficient and I have the CPU underclocked and wayyyyy undervolted. If I unplug my 7950s and plug in an old PCI videocard then boot to desktop, the system idles at only 55 Watts.


Thanks for posting this info, I was just about to ask.
Your setup seems to be running nicely. Have you tried running your memory even lower than 1250 (i.e. ~900)? I was able to drop over 40 watts by taking the memory down from 1250 -> 900 and I didn't lose any hash rate.

Oh, ok.  That's quite good.

But you still would be at (or near %) capacity of psu which kills your power efficiency.  You must also be running other low draw hardware (like ssd/lower mem/ semperon/Ect).  Like I said it depends on a ton of factors.  And every online calculator I have seen would recommend a larger psu for those 3 cards.


Edit...re-read your post...you are at about 97% of capacity.

sorry i ment to say i have 3 7950s runing at 630kh each

edit 1050 core 1250 ram 1.050v core 55% fan

That's easy...some cards only pull 15watts!

The poster I was referring to was running 3 7950s (underclocked).

If he was running these under load (scrypt mining/over clocked) he would not be able to run them with a 850psu.  Additionally he would be burning a lot of wasted power because of the efficiency drop.

It sounds like you're having fun with coins and mining! That's great.
Be careful out there, gambler.

The LTC difficulty is (relatively) nice right now so it's definitely prime time for mining it.

Here's the tool I use to check my power usage: http://www.amazon.com/P3-International-P4400-Electricity-Monitor/dp/B00009MDBU

It's also possible to use an AC line splitter and a clamp-style ammeter to calculate your wattage.

Example clamp meter: http://www.amazon.com/Sinometer-UT202A-Auto-ranging-Clamp-Meter/dp/B005FSSKJA
Example AC line splitter: http://www.amazon.com/Tekpower-M920-AC-Line-Splitter/dp/B003A0MD48

i run 3 cards on a 750w psu ( 700-725w  at the wall )

Nice post Xanthe,

I am surprised even with underclocking your 3 7950s you can get by with only a 850psu.  These cards supposedly draw up to 300w under full load (depending on what coin you mine).  Then trying to power other peripherals make it seem like your power supply would be running at 100% capacity(or more).  Even simple calculators would recommend at least at 1000 for those three cards.

http://support.asus.com/powersupply.aspx


Also, When you draw at such a high percentage of the rated capacity you loose power efficiency.  Supposedly running at around 50-70% gives you the best power efficiency.  Above those numbers you are burning more electricity in regards to heat.  Even using a high efficient power supply..like a 80plus gold.


http://en.wikipedia.org/wiki/80_Plus


Anyhow,  seems like you have yours dialed in to give you results and performance you are looking for!

if you get 7950s buy the saphire vaporx oc edition they are worth the extra mony ( 630kh vrm under 80c core under 60c room temp 27c )
if you need 7950 seting pm me  ( i get 1,950kh with 3 cards 730w from the plug and over 2,550 with 4 cards just over 900w from the plug  )

Thank you so much for this detailed response!  I'm currently mining FTC and LTC.  I was mining BTC but the pool I was in (Triplemining) went down and I decided to move on.

My electricity cost is pretty insignificant ($0.06/kwh) but I will look into undervolting them if I can get the 3 card set-up to work.  I would love to have 3 7950s, but I imagine I will end up getting another 5850 or something that I can find on Craigslist for under $100.  I might need to check out one of those fancy multimeters (?) so I can measure my wattage at the wall.  If my math is right, 850W running at max for 24 hours a day, would only be $36 at my kwh rate, so I am not too concerned with it since anything over 600MH(or KH)/s should be sufficient to profit. 

Right now I'm cranking out 700-800KH/s so I am just really trying to get it up to 1+MH/s and then put it in the corner, set up cgwatcher to mine the crap out of it, and then gamble with all of the coins 

Definitely wouldn't mind getting a 7950 in it though... that would boost the speed significantly.

There are so many factors it's really hard to say why that setup didn't work out. It's possible that the 12V rail(s) on the 630W were simply not up to the task (PSU wattage does not tell the whole tale). Antec likes to put multiple +12V rails on their PSUs. Each rail has its own OCP (over current protection) and sometimes on the lower wattage PSUs (650 and under) a single rail simply won't provide enough amperage for mining without tripping. This or any number of other things could have been causing your issue.

I looked into the Antec 850 that you have and it seems decent. It has four +12V rails which are distributed a little oddly but I doubt will cause you problems. According to this review: http://www.hardwaresecrets.com/article/Antec-TruePower-Quattro-850-W-Power-Supply-Review/555 the OCP for each +12V rail doesn't trigger until 32A (the official rating says 18A). If you decide to try three cards, I'd certainly recommend that you undervolt them if possible to reduce the total load on the PSU and also save on your power bills. The stock voltage setting for cards is usually wastefully high and can safely be backed down a bit to lower temperatures and increase efficiency. It's usually not a good idea to run your PSU at 90%+ of its rated capacity as it greatly reduces the expected lifetime of the PSU. Efficiency and voltage regulation capabilities also drop off sharply around this point.

Anyway, I really do believe that your Antec 850 will be enough still, especially if you can undervolt your cards. Also, you never mentioned what you're mining. SHA256 (Bitcoin) mining uses less power than scrypt (Litecoin) mining.

I'm currently running 3 7950s on an 850W PSU (XFX PRO850W) without issue. I did undervolt my cards quite a bit though. At the stock voltages of 1.2V on these Sapphire cards, I was easily running at 90%+ of my PSU's capacity mining Litecoin (~900W measured at the wall). By undervolting the cards significantly and lowering the memory clockspeeds, I was able to get the total system power usage down to 620W at the wall.

Current setup:
3x 7950s
570Kh/s each, 1,710Kh/s total (scrypt)
.985V core
955Mhz core
900Mhz memory EDIT: just double-checked and corrected this value.
620 watts, measured at wall (via Kill-A-Watt)

My hash rate is a bit lower than the numbers often bandied about but since my power costs are fairly high, I've realized that efficiency is more important. My cards will run up to 650Kh/s but the extra power used to get there isn't worth it anyway.

With a bit of tweaking, I think that you can make your setup work out as well. As long as you can lower voltages, your 850W will be more than enough. Good luck!

First off it depends on what other hardware (CPU/motherboard/hard drive/etc) you are running.  Regarding the cards, look at this chart to see their power consumption:

https://en.bitcoin.it/wiki/Mining_hardware_comparison

You will likely have a hard time running 3 cards stable but it does depend on what cards and what other hardware you are powering.

Hmmm... so why was 630W not enough for 2 cards? 

I guess that's why I am confused.  But I hope you are all right because i would love to be able to get another card running and not have to mess with the PSU again

i have 3 7950s on a hx750 only 730w from the wall

buy a plug in watt metter and look at your wattage ( 7950 vaporx is unde 250w at 630kh )