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canoli
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850W / 70A enough for two 780s?

Fri Apr 24, 2015 9:14 pm

I want to add a 2nd GPU for CUDA rendering. It won't drive the displays it will only run fluid sims generated by TurbulenceFD, a Cinema 4D plugin.

The PSU is a Corsair HX850. I have a 6GB GTX 780 card and want to add another. I realize Maxwell is more efficient but the 780 with higher memory bandwidth and a larger frame buffer is better suited to run TurbulenceFD.

The 780s are "rated" as 250W cards. Can the HX850 run 2 of them? The rest of the system: 24GB DDR3, i7 980X, two SSDs, three HDDs, two optical drives, 4 fans.

Thank you guys for any thoughts you can share.
 
vargis14
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Re: 850W / 70A enough for two 780s?

Sat Apr 25, 2015 12:52 am

Your corsair 850 PSU is plenty to drive 2 780's. I am running 2 EVGA GTX 770 4gb classifieds in SLI with a older corsair Corsair TX850 v2 that is as old as my 4 year old Sandy bridge 2600k system OCed to 46-5000mhz. I know for a fact that with my 2 770 classifieds that use 2x 8 pin PCIE power connectors per card use as much wattage as a GTX 780 with the clocks on the core and memory I am running at +15% power.

Just put in the second 6GB 780 and SLI them and enjoy all those cuda cores...Plus it will help gaming a lot. Unfortunately when I got my 1st EVGA GTX 770 Classified 4gb card the only 780 classifieds that were out were 3gb and the 780ti was yet to be released so I figured with the extra high clocks my 770's had the potential to run at compared to the 780s lower clock speeds it would pretty much balance out the difference in performance. Plus I knew I was going to be running a Hi resolution monitor. Currently running a new LG 34UM95 34" 21/9 3440x1440 resolution IPS 8 bit/10bit with dithering and a 99% sRGB color rating running at 60hrtz. My SLI'ed 770s have performed fantastic and I hope they continue to do so with DX12.

Oh and just so you know I am jealous of your 6gb of VRAM but seriously when you use a SLI bridge connector and SLI is disabled it will just use the primary card for your video output and will not alternate frame render. Or you can use SLI and use the second card to do all your post effect like 32x SLI AA and stuff like that. I think for your reason for installing a second 6gb 780 for your fluid dynamics/Fire Dynamics you will need to use a SLI bridge anyways, I could be wrong but I do not think so. BTW I checked out the webpage and it looks neat. Let us know what kind of performance increase you get by adding the second 780 6GB card. I would love to see how it worked on my 4gb 770's and my 4660mhz ATM sandy system compared to your killer 980 6 core monster and 6gb 780's.
I am curious if your CPU speed makes a big difference in your TurbulenceFD application. Ifit does I would definitly see what kind of overclock you can get on your CPU without increasing the stock voltage to your CPU. The least you can do is make sure you have your turbo settings to use all 6 cores at the max stock turbo of 3.6ghz or try 3.8ghz if Turbulence uses all 12 threads. If that is the case you will get a decent increase in performance just by letting all 6 cores run at 3.6-3.8ghz turbo speed instead of them dropping to from 3.6ghz to 3.3 ghz. If they have a free to try version of the program and you have a simulation to run I would love you to send it to me and let me try running the simulation on my rig to compare it to yours.

PM me if interested. It just might make you want to get a 4790k Haswell system or a even more powerful Haswell-E system with 6 or 8 cores. I know my i7-2600k is almost as old as your i7-980 but My sandy bridges performance per core is better then the 980's and Ivy and Haswell increased that about 6% for Ivy and for Haswell to be about 16% faster clock for clock to my Sandy..unless it comes to gaming then it is way lower under 5%
2600k@4848mhz @1.4v CM Nepton40XL 16gb Ram 2x EVGA GTX770 4gb Classified cards in SLI@1280mhz Stock boost on a GAP67-UD4-B3, SBlaster Z powered by TX-850 PSU pushing a 34" LG 21/9 3440-1440 IPS panel. Pieced together 2.1 sound system
 
Chrispy_
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Re: 850W / 70A enough for two 780s?

Sat Apr 25, 2015 1:36 pm

It'll be close, but should be okay - 100W to spare or so.

Power supply calculators agree with Vargis but that includes no ageing (capacitor wear) on the PSU.

http://www.extreme.outervision.com/psucalculatorlite.jsp

The problem is really the age of the capacitors in the PSU. Most people suggest 10% per year and if it's the same age as your 980X you could find that you PSU gives up with two 780's and the CPU at full load. If I assume the PSU is five years old and would still be capable of 850W after the three years of warranty (that's usually how PSU manufacturers decide on how much headroom above the rated wattage) then your PSU has something like a 20% reduced peak output now and is now a 710W PSU.
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canoli
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Re: 850W / 70A enough for two 780s?

Sat Apr 25, 2015 3:12 pm

thanks you guys for your replies, I appreciate it very much.

Vargis: TFD is easy to try for free but of course you need C4D (or Lightwave) to host the plugin. TFD is capable of generating its sims through a CUDA-enabled GPU or the CPU but naturally the parallel processing on the GPU is much (much!) faster. What's cool about TFD is the UI has a drop-down where you choose the engine you want, before you run the sim, and whatever is installed on the system is listed there - GPU(s) and your CPU. But even 12 threads at 3.75Ghz are no match for a modern CUDA card. Jawset recommends a >4GB frame buffer though TFD will still run on cards with less...but once the cache fills up TFD automatically switches to the CPU. I've timed my i7 980x against the GTX 470, the 770 and the 780 and it's not even close: the CUDA cards always finish at least 4 times faster.

I won't be using an SLI bridge. The 2nd card will run the sims without the burden of driving the viewport (or any display) at the same time. Though it's tempting to see what 2304x2 CUDA cores could do, along with 198x2 texture units and 48x2 ROPs. Hmm maybe I should experiment...see what happens.

http://help.jawset.com/en/c4d/

Chrispy: I'm a little worried about the cap aging. The whole system incl the PSU is indeed almost 5 years old and during that span it's processed many long renders (30+ hours). I wouldn't be surprised if the PSU is nearing its EOL.

The HX850 supplies 70amps on the +12v rail. How that's possible when it's plugged into a 15A circuit (or a 20A) is beyond me....but I don't really need to know.

I guess there's no substitute for experimenting - what's the worst that can happen? Anything's possible but would you agree the most likely result is the PSU just dies? Even though X58 is old - and even though I'm itching to build an X99 system - I'd rather not risk frying the mobo right now. But I can't see how that would happen just by stressing the PSU... ??

thanks again you guys!
 
sluggo
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Re: 850W / 70A enough for two 780s?

Sat Apr 25, 2015 3:28 pm

Chrispy_ wrote:
It'll be close, but should be okay - 100W to spare or so.

Power supply calculators agree with Vargis but that includes no ageing (capacitor wear) on the PSU.

http://www.extreme.outervision.com/psucalculatorlite.jsp

The problem is really the age of the capacitors in the PSU. Most people suggest 10% per year and if it's the same age as your 980X you could find that you PSU gives up with two 780's and the CPU at full load. If I assume the PSU is five years old and would still be capable of 850W after the three years of warranty (that's usually how PSU manufacturers decide on how much headroom above the rated wattage) then your PSU has something like a 20% reduced peak output now and is now a 710W PSU.

I have to chime in.

I've seen this "most people suggest 10% per year" or variations on it several times now. It's just not true. Aluminum electrolytic capacitors from reputable vendors will experience a decay in capacitance value over their useful life, but the decay is more like 15-20 percent over a period of 15 -17 years (given normal operating conditions). This works out to a little over 1% per year.

Second, the decay in the capacitance value of a capacitor in the supply doesn't directly translate to a decline in the current capacity of the supply. Making a one/one correlation like that ignores a lot of relevant circuit complexity. If there's some question about the state of an older PSU, it's probably better to ask "how much heat was it exposed to and for how long?".
There is nothing more frightful than ignorance in action - Goethe
 
vargis14
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Re: 850W / 70A enough for two 780s?

Sat Apr 25, 2015 5:02 pm

Canoli I have to agree with sluggo. MY PSU is 4 years old and is a seasonic produced TX850v2 watt unit produced for Corsair and I have had my CPU and GPU overclocked since day 1 including the 2 SLI'ed EVGA GTX 560 Ti SuperClocked cards running at 1ghz on the cores and I think 2400 on the memory with a .1v voltage bump for stability that are now replaced with the 2 4GB SLI'ed EVGA GTX 770 Classifieds running at 111% power on both cards, stock volts on primary card and 1.2v on secondary card with a very small overclock so they both boost sustained and never throttle below 1280mhz core and the 4gb of memory memory is running at 7996 mhz and my fans on my profile go aggressively from 29% in a steep arc to 100% at 55c...just checked my 24/7 setting I use with EVGA's Precision X software. I also have a movie watching setting that keep the fans below 45% to 75c but they never break that even though my MadVr settings do use 99% GPU usage it just is not like a gaming 99% load with over 2gb of Vram being used.

I wish I could have Johnny Guru come to my house and test my PSU and see what wattage my PSU can do after 4 years of 24/7 use.

In fact Canoli you should visit his site and see if he reviewed your particular PSU. If so he will tell you who made it for Corsair and will have it taken apart to see what components were used in its contruction and let you know if they are good components or bad, solder job, How it works cold, How it works Hot, power ripple under load...the works. He is very informative. I got lucky when I purchased my Tx-850 v2 I had no idea it was made by seasonic....but I read his original TX850 v1 review that was not a seasonic unit and it got great marks so I figured I could not go wrong with Corsairs V2 version and Luckily seasonic made it whoo hoo:)
Anyway here is Johnnys review of your Professional grade HX-850 http://www.jonnyguru.com/modules.php?na ... y&reid=153
Well it states it will last 100,000 hours and if you have ran it 24/7 for 5 years that would be only 43,800 hours. It also has a nice 140mm adjustable fan according to the load/temp on the unit, I like that feature Now that my PC is right next to me. Voltage ripple is quote:Outstanding. If I were choosing my next power supply based on ripple suppression alone, I'd be mighty tempted to say, "So long Delta plan!" fantastically efficient
12V ripple suppression second only to a very few high end units
very, very stable regulation
Rated 9.6 outta 10 it is a fantastic PSU....read the article you might want to tighten the loose screws that you possible have. I did it to mine it was very easy I didnt even have to unplug my MB or Graphics cards...just do it on a big enough table that it does not fall and jerk on your connections! That could be very bad.

You have no worries, enjoy the extra Cuda power and use a SLI bridge :) When I have time I will click on that link and mess around maybe and see what my puny 4GB 770's can do. "Big extra wide slightly flabby 770 guy flexes next to a 780 body builder with no body fat " My 770s are like 1.5-2" wider than a stock 780 and have 14 power phases :roll: , also a stock 780 has 6 power phases for the core and probably 2 for 6gb of memory.
I am curious, what case are you running and what brand 780's and cooler type....Blower, open air? If your case has spots for side panel fans the type of 780's you have will let me know if the side panel fans should be on intake or exhaust. If they are blowers intake all day long without a worry, If they are open air the best fan configuration could be exhaust or intake depending on which way the fins run on the cards heatsink. This is why I am asking for the exact brand case and cards. I am concerned since I had a real problem with my huge 6 heatpipe Classified cards running over 80c and hitting 90+ on occation with 2 120mm fans blowing in right on the cards and 18c ambient temps! That lasted a whole 2 days but It turned out my 2 Cougar Vortex 120mm intake fans focused so much airflow at the side of my graphics cards that were trying to expel the heat towards the side panel and motherboard making a dead spot on a large area of the heatsinks that have 2 92mm fans trying to push air away from the card......switching the fans to exhaust dropped temps 20-25c. This is why I ask since a cooler running card or CPU in fact uses less voltage than a hot ones...same goes for PSU's, the hotter they are the more voltage they pull from the wall to give you the same wattage lowering your PSU efficiency.
Also I cannot recommend the Cooler Master Nepton 140xl AIO cooler enough, for the 89$ I spent on it with 2 Jetflow 140mm fans in push pull configuration that are silent when controlled by the CPU fan header running between 700 and 1100 rpms it is pretty inaudible and my soldered on IHS is transferring the heat so good. At 4660mhz at 1.345 v @ 19c ambient I am idling at 22c and loaded with Intel BT2 not breaking 57c at 1100rpms. I am sure your i7-980 would run super cool with its soldered on IHS and the Nepton 140XL has a 38mm thick radiator a huge copper cold plate with extra micro fins that surpass the DIY cooling blocks, along with a extra powerful pump hooked to about the largest diameter Coolant lines on the market right now. With as thick as the radiator is and being 140mm it is like having a 240mm radiator for the most part, but having the high static pressure fans in push pull makes up for the extra thick radiator big time.
So how did you like my book Canoli? Does it need much more work? :wink: I have been working all week 10-12hr shifts so I have been flopping and passing out right after I eat when I get home.
2600k@4848mhz @1.4v CM Nepton40XL 16gb Ram 2x EVGA GTX770 4gb Classified cards in SLI@1280mhz Stock boost on a GAP67-UD4-B3, SBlaster Z powered by TX-850 PSU pushing a 34" LG 21/9 3440-1440 IPS panel. Pieced together 2.1 sound system
 
canoli
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Re: 850W / 70A enough for two 780s?

Sat Apr 25, 2015 9:09 pm

thanks Sluggo, very interesting article on cap aging. Not that I understood it completely ... "probability density function" took me a few passes ... but an interesting read all in all. Earlier I said I wouldn't be surprised if this PSU was nearing its EOL but after reading the article I doubt that's true.

JohnnyGuru's site is a tremendous resource - thanks for the link Vargis. I've read his stuff over the years but never checked out my own PSU till recently. Good to see he gives it high marks. 'll check the heat sink screws...it's about time for a thorough cleaning anyway - thanks for the heads-up.

So I guess I've got my power question answered - thanks again guys.

btw Var - the 770 did a great job with TFD. I only went to the 780 b/c EVGA was offering it on their StepUp program - and I wanted the 6GB cache of course. As you can imagine the extra 2GBs make a huge difference at HD rez: TFD rarely needs to switch to CPU rendering.

HAF X case, excellent for air cooling - it ought to be considering its size (it's humungous) and its three 200mm fans - 2 intake (front/side) 1 exhaust on top - along with a 140mm rear exhaust fan. All the extra room allows for superb circulation - for awhile I thought the sensors were stuck (!) - it idles in the high teens and under load rarely hits 65C. For once Intel included a respectable HSF http://www.hardwaresecrets.com/article/Intel-DBX-B-CPU-Cooler-Review/1000/1

EVGA GTX 780 6GB, 06G-P4-3787. It's never hit 70C yet even running a long fluid sim - no fan profile, stock everything. I had Precision for awhile, ran it OC'd but frankly I didn't notice any difference except it ran a bit hotter.
 
vargis14
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Re: 850W / 70A enough for two 780s?

Sun Apr 26, 2015 7:10 am

I remember that Intel tower cooler, I believe it was only offered on your top of the line 1366 x58 CPU. It would have worked better if it used a fan or fans that had shrouds that would force the air through the fins. But if your a happy camper then you are good to go.
I am also using a HAF case the so called mid tower 922. I agree they have great air flow.

I have the same coolers on my 770's if your using the side panel fan option make sure it is on exhaust it will help with GPU temps, your GPU heatsink fins are in the same configuration as mine, just mine had a extra heatpipe and is 1.5+ inches wider ...besides that they are identical.
BTW glad to help when I can.
2600k@4848mhz @1.4v CM Nepton40XL 16gb Ram 2x EVGA GTX770 4gb Classified cards in SLI@1280mhz Stock boost on a GAP67-UD4-B3, SBlaster Z powered by TX-850 PSU pushing a 34" LG 21/9 3440-1440 IPS panel. Pieced together 2.1 sound system

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