Data point for "Is this enough of a PSU for this card?" question.

[torin3]

PSU - Corsair 750W semi-modular, Model: CX750M 80+ Bronze.

February 2014.

Ran 2 7970s, then 2 970s, then 2 1070s.

Yesterday morning, it smelled of ozone in my office and the computer was off. I thought it was the UPS initially, but after it shut off when I'd switched out the UPS, I figured it was the PSU. Removed PSU, and it smelled very strongly of burnt electronics. Couldn't see any burn marks or popped caps. Replaced PSU and computer is working, though with only 1 card at the moment (replacement 850w PSU should arrive today or tomorrow.

Computer has always been on a 1500VA UPS.

So, I'd put 750 watts right at the minimum of being able to power 2 1070s. You can do it, but it looks to be a bit hard on the PSU long term.

 

[Johan45]

Thanks Torin3, was that a 24/7 folding machine?

 

[Alaric]

Interesting. If it ran two 7970s I would have thought two 1070s would be like a day off.

 

[torin3]

Thanks Torin3, was that a 24/7 folding machine?

Yep, 24/7 mining for a year then 24/7 folding after that.

 

[wagex]

Interesting. If it ran two 7970s I would have thought two 1070s would be like a day off.

my thoughts, 7970 has a 300w tdp and gtx 1070 has 150w i think.

sounds like just being rode hard for a long time.

 

[EarthDog]

PSU - Corsair 750W semi-modular, Model: CX750M 80+ Bronze.

February 2014.

Ran 2 7970s, then 2 970s, then 2 1070s.

Yesterday morning, it smelled of ozone in my office and the computer was off. I thought it was the UPS initially, but after it shut off when I'd switched out the UPS, I figured it was the PSU. Removed PSU, and it smelled very strongly of burnt electronics. Couldn't see any burn marks or popped caps. Replaced PSU and computer is working, though with only 1 card at the moment (replacement 850w PSU should arrive today or tomorrow.

Computer has always been on a 1500VA UPS.

So, I'd put 750 watts right at the minimum of being able to power 2 1070s. You can do it, but it looks to be a bit hard on the PSU long term.

I think psu crapped out, period. That psu can easily handle everything you threw at it. The 2 7970s were worse at 250w each...the 1070s are 150w cards... it wasnt the 1070s which did it, they just happened to be installed at the time.

Id fold with 2 1070s on a quality 550w psu, never worry, and still have plenty of headroom.

You should grab a kill a watt amd see how much power that system is actually drawing.

 

[caddi daddi]

like earthdog says, get a killawatt you'll be surprised how little the system is actually drawing. few cards will ever draw near tdp unless you clock it to get there.
my 2 1060's in a 6800K rig will never pull over 350 watts, and tends to 325-330 total system draw rendering at very high clocks.
if you have voltage adjustment, that changes things.

 

[SPL Tech]

750 is more than enough. You could run three overclocked 1070s and still be fine. I've had my 750W PSU for almost 10 years and I've ran several rather serious SLI setups. I had a set of GTX 265s in SLI and those things were complete power hogs. Overclocked them and ran the CPU at a high voltage and heavy overclock. I ran the computer so hard I burned up the VRMs on the mobo after a year. That was four builds ago and I am still using the same PSU. I started out with 8800GTS cards and now I am running a 1080Ti. Havent changed the PSU once and it was Corsar's second from the bottom of the line at the time I bought it. Corsair seems/ seemed to make some pretty solid PSUs.

The number of PCI-E plugs that comes with the PSU is an indication of whether it's powerful enough or not. In short, as long as you havent used ALL your PCI-E plugs and you're using adapters to create even more PCI-E plugs, you're not going to be over the limit. A 750W supply is going to come with four PCI-E plugs, so any two cards requiring two 8-pin PCI-E ports (or less) will be acceptable. The GTX 1070s usually only have one port each so you theoretically could even get away with FOUR GTX1070s and probably still be fine on a 750w supply, although you'd probably be right at the limit.

I have a Killowatt meter. Using the computer in my signature, I draw around 450w while gaming. Note that is the power the SUPPLY draws, not the equipment itself. The supply is not 100% efficient and so it draws more power than the computer components use which means if it's drawing 450w from the outlet the computer is probably using around 420w.

 

[Alaric]

In defense of the CX750M, I've had one running an OC'd hex core FX for a few years and it's still chugging along just fine.It's just a little more than the rig needs (on purpose) so I expect it to keep on keeping on for a while longer.

 

[EarthDog]

The supply is not 100% efficient and so it draws more power than the computer components use which means if it's drawing 450w from the outlet the computer is probably using around 420w.

Or to put actual math behind it...

If a your psu is gold and 90% efficient, it will be taking 10% more from the wall. So if your PC is actually using 450W, it will draw 495w from the wall/what the kill a watt says.


Cx750m is serviceable. Not great. Most expect it to 'work'. Id bet its a lot more than your system needs, not a little.


Anyway, i hope people who see this thread read past the first post... a 750W psu isnt close to the minimum for 2 1070s... bad datapoint.

 

[gsrcrxsi]

dont worry about the total power rating. the total rating includes the 5v and 3.3v lines as well as 12v

only worry about what the 12v rails can supply. that's more realistic.

who cares if you have an 800w PSU if it can only supply 500W via 12v...

also if it's multirail, keep in mind what youre powering with what rail. when i first built my system I wanted to keep the wiring clean, so i didnt plug in more connectors than necessary. I needed the 8-pin CPU and 2x 8-pin PCIe connectors, which were all available hardwired to the PSU. I have the option for 2 more PCIe but didnt think I'd need them. well even though my PSU has 4x 12v rails all of the hardwired options come from the same rail with a 25A limit. the first stress test I ran, the computer promptly shut down from exceeding 25A on that rail. So i had to plug in one of the extra PCIe 8-pin cables to distribute the load.

 

[petteyg359]

750 is more than enough. You could run three overclocked 1070s and still be fine. I've had my 750W PSU for almost 10 years and I've ran several rather serious SLI setups. I had a set of GTX 265s in SLI and those things were complete power hogs. Overclocked them and ran the CPU at a high voltage and heavy overclock. I ran the computer so hard I burned up the VRMs on the mobo after a year. That was four builds ago and I am still using the same PSU. I started out with 8800GTS cards and now I am running a 1080Ti. Havent changed the PSU once and it was Corsar's second from the bottom of the line at the time I bought it. Corsair seems/ seemed to make some pretty solid PSUs.

The number of PCI-E plugs that comes with the PSU is an indication of whether it's powerful enough or not. In short, as long as you havent used ALL your PCI-E plugs and you're using adapters to create even more PCI-E plugs, you're not going to be over the limit. A 750W supply is going to come with four PCI-E plugs, so any two cards requiring two 8-pin PCI-E ports (or less) will be acceptable. The GTX 1070s usually only have one port each so you theoretically could even get away with FOUR GTX1070s and probably still be fine on a 750w supply, although you'd probably be right at the limit.

I have a Killowatt meter. Using the computer in my signature, I draw around 450w while gaming. Note that is the power the SUPPLY draws, not the equipment itself. The supply is not 100% efficient and so it draws more power than the computer components use which means if it's drawing 450 from the outlet the computer is probably using around 420w.

That'd be 93% efficiency at ~ 60% load (450/750). I doubt most people are running 80+ Titanium PSUs these days, given they're still quite expensive. Though that'd only be at the Gold/Platinum level on a 240V circuit. Given your PSU is only Bronze, I suspect the real system load is closer to 380 W than 420 W.

 

[SPL Tech]

Or to put actual math behind it...

If a your psu is gold and 90% efficient, it will be taking 10% more from the wall. So if your PC is actually using 450W, it will draw 495w from the wall/what the kill a watt says.


Cx750m is serviceable. Not great. Most expect it to 'work'. Id bet its a lot more than your system needs, not a little.


Anyway, i hope people who see this thread read past the first post... a 750W psu isnt close to the minimum for 2 1070s... bad datapoint.

Except that is not actual math because the efficiency ratings are:

1. An average across many units which will change from unit to unit and depending on several conditions including exact input voltage and temperature of the PSU.

2. The most efficient point of the cycle. The PSU's efficiency will change as the load changes. It wont have the same efficiency value at 20% load as 80% load.

If the unit is labeled as being 90% efficient then it's actual efficiency is likely going to be 80 - 90% at any one given time. The rated efficiency is the best you will ever get, not what you will get on average. Sort of like when a car says it gets "up to" 40 MPG.

 

[EarthDog]

1. Lol, dont split hairs....and No.
2. True. However youd be surprised at how little difference there is between those values. A couple percent at best with modern psus. Look at a jonnyguru article... for example, my 750w gold...varies by 2% from 150w to 750w.
http://www.jonnyguru.com/modules.php?name=NDReviews&op=Story4&reid=380

Here is a ckrsair hx850 from 2009 showing 2.5% difference...
http://www.jonnyguru.com/modules.php?name=NDReviews&op=Story3&reid=153

Point is, after around 10-15% load, its an incredibly flat curve for efficiency. Titanium psus vary even less down low as they include a 10% load spec.


You'll get what its rated at when at the given wattage... feel free to peruse any jg review for halfway modern and not crap psus for additional proof.

 

[petteyg359]

Except that is not actual math because the efficiency ratings are:

1. An average across many units which will change from unit to unit and depending on several conditions including exact input voltage and temperature of the PSU.

2. The most efficient point of the cycle. The PSU's efficiency will change as the load changes. It wont have the same efficiency value at 20% load as 80% load.

If the unit is labeled as being 90% efficient then it's actual efficiency is likely going to be 80 - 90% at any one given time. The rated efficiency is the best you will ever get, not what you will get on average. Sort of like when a car says it gets "up to" 40 MPG.

Nope. The 80+ efficiency ratings are minimums from 100% down to 20% load. If it's 80+ Titanium, then the efficiency rating of 90% extends down to 10% load.

80 Plus test type|115V internal non-redundant||||230V internal redundant||||230V EU internal non-redundant|||
Percentage of rated load|10%|20%|50%|100%|10%|20%|50%|100%|10%|20%|50%|100%
80 Plus||80%|80%|80%||||||82%|85%|82%
80 Plus Bronze||82%|85%|82%||81%|85%|81%||85%|88%|85%
80 Plus Silver||85%|88%|85%||85%|89%|85%||87%|90%|87%
80 Plus Gold||87%|90%|87%||88%|92%|88%||90%|92%|89%
80 Plus Platinum||90%|92%|89%||90%|94%|91%||92%|94%|90%
80 Plus Titanium|90%|92%|94%|90%|90%|94%|96%|91%|90%|94%|96%|94%

 

[EarthDog]

I even linked that above earlier...

Edit.. oops that was in tyes thread....

But yeah, that wiki page has an image that shows the tiers.. they are MINIMUMS. It is NOT an average, thats for sure.



This thread is just full of misinformation from the get go.

 

[SPL Tech]

Nope. The 80+ efficiency ratings are minimums from 100% down to 20% load. If it's 80+ Titanium, then the efficiency rating of 90% extends down to 10% load.

Thanks for correcting that. You are correct, although there is a difference between claims and truths. Just because that's what the standard says and just because companies say they meet the standard doesent actually mean the PSU in your hands will match that chart. It's not exactly a secret that companies often stretch the truth and make fictitious claims. *cough* GTX970. Claimed 4 GB of usable RAM and we quickly learned that was basically an outright fabrication.

 

[petteyg359]

Thanks for correcting that. You are correct, although there is a difference between claims and truths. Just because that's what the standard says and just because companies say they meet the standard doesent actually mean the PSU in your hands will match that chart. It's not exactly a secret that companies often stretch the truth and make fictitious claims. *cough* GTX970. Claimed 4 GB of usable RAM and we quickly learned that was basically an outright fabrication.

And now you're grasping at straws...