Topic: Is my Kill a Watt wrong? says pulling almost 1300W from 1200 W PSU? (Read 7835 times)

Will definitively try that bios pretty soon! 1.090V is GOOD

Besides the power savings, the cards I run with the 1.09V BIOS are about 10 degrees C cooler vs the 1.25V BIOS.

I know, I'm loosing money , but efficiency is my main concern, I'm right now at 2.5MH/W , If i clock up in linux, efficiency goes down like a rock!, In windows is another matter because with trixx I can lower the voltage and maintain efficiency or better at higher clock speeds.

that's why I am messing with modify the card's bios to lower default voltage, once I get enough feedback and information, I will go with it

You might want to look into your settings, you are running super slow. While you are saving a little bit by having lower power consumption, you are also losing a ton of $/Mhash by running expensive cards at low speeds.

I don't know about 7970, the ones i ordered are coming this monday, but my 3 x 7950 are using 510W (at the wall) right now, 1.4 GH @ 1.125v, Will try this mod to lower it to 1.100V first, then 1.050v, I'm pretty sure it would reduce the power consumption at least for 80W or more, but yes, modify the bios by hand is dangerous hehe

Altsay:
Yes the PSU i am using is 5% LESS efficient than a coolermaster GX (tested it, but have to change it anyway because my GX is only 650W and using 500W from a 650W PSU scare the shit outta me, so I stick with the Sentey SDP850SS (850W), less efficient but more secure, more than 300W spare.

Power consumption is higher than the amount on the label depending on the efficiency rate of the psu

lol

Should it? At stock voltage I run 2x7970s and 1x7950 at 800W (1900MH/sec) on Kill-a-watt. OP draws 200Watt more on 7950s with modded bios? Doesn't seem like good advice for the kiddies.

Hello
This thread is GOLD should be sticky!

Until now i was using trixx to operate the 7950s at 1.100V but now that I've switched to linux, i am toasted!, no voltage control!

I was thinking, why not, modify the original bios card with a fixed voltage?
I made a small investigation in the matter, I would like to hear your opinions before try it in one of my cards.

here it is: Lower voltage of Sapphire 7950 to reduce power (linux-usb)firmware mod

I am just flashing them on my Windows rig to out them in the BAMT rigs.


I was testing them mining before I shut the BAMT rigs down and change the cards.

But why did you flashed the BIOS on those cards running Windows in the first place?
Why not use Afterburner to undervolt to your liking?

I only mentioned BIOS flashing to BAMT running cards, since there is no way to undervolt in Linux.

I havent tried mining BTCs yet except for a min so I cant say about that but mining LTCs I get the same hash rate on the x1 slots as I do on the x16 slots.


This is wierd though.


On my Windows 7 rig I have 3 cards.  All the same Sapphire 7950's 20G model.


The cards show up as 0, 1, and 2.  Card 0 is the card my monitor is plugged into.



Card 0 already has the BIOS you linked me to.  Cards 1, and 2 have the stock BIOS.  All three cards run 625 KH/s like this.


I flash the BIOS you linked me to to card 1.  (I use a DOS bootable USB with ATIFlash to flash.)

So at this point cards 0 and 1 have your BIOS, and card 2 has the stock BIOS.

I boot info Windows and run cgminer.  Same settings and everything that I used to run 625 KH/s before. 
Cards 0 and 1 mine fine, 625 KH/s but card 2 mines at 450 KH/s.  I never did anything to card 2.  All I did was flash card 1 over to your BIOS from stock.

So I figure maybe because its the only one on a different BIOS.  I dunno I know prob not but whatever.

So I flash card 2 with your BIOS.

Boot into Windows and run cgminer.   Now cards 0 and 2 run fine, 625 KH/s but card 1 now runs 425 KH/s.




I tried deleting any .bin files and it never helps.  I dont understand how this could be.


And I tested with 2 other BIOSs on the BAMT rigs and they will not no matter what boot with cards in the x1 slots unless they have the stock BIOS.  I tried both regular booting and safe mode and it will get to the part where X is supposed to start and then the screen will flash a couple times and then it just goes blank.  The monitor is still on but there is no display on it.

Stock voltage I presume?

I run 3 7950's in one of the rigs with a 850 W power supply. Kill-a-Watt hovers @ 700 Watt. 

I tried to figure it out if the problematic cards (those that refuse to work at 1.09) are a different brand.
Cant say why they are refusing to work at 1.09. All my cards they work the same no matter the type of slot I put them in.
(Those in X1 slots they do hash a bit slower though...aprox 40Mh/s lower.)

At the time I had 4 cards running at stock voltage the consumption was around 1170W. By lowering the voltage to 1.09 it went down to 788W.

My problem now is that my rigs will not work any of the X1 slots with any bios except for the stock one.



And just so others know, by switching just 3 of 5 cards to a 1.09V BIOS instead of the stock 1.25V BIOS my power draw went down almost 250W.  I was pulling 1250-1275W before and now it pulls 990-1010W.


Others have posted that going from 1.25V to 1.15V saves about 50W.  So going from 1.25V to 1.09V saves around 83W.


Seem right?

All of my cards are the same brand and model.  They are all Sapphire 7950's.  The 20G model.

Which one card are you talking about? The one that is on the PSU with the 3 with the new BIOS?


Just to ease confusion the rig I was talking about that's drawing less power has 5 cards.  All the same.  4 are on one 1200W PSU and 1 is on a smaller 700W PSU.  3 of the cards have the BIOS you linked me to and 2 of the cards have the stock BIOS.

The 3 cards that have the BIOS you linked me to are on the 1200W PSU.

That card at 1.25 V is a different model?

Figured out the power issue.  It was because all of the cards were running at 1.25 V.


Right now I have 4 cards hooked up to the 1200 W Silverstone Gold PSU.  3 of the cards are on the BIOS you gave me running 1.09 V, and one cards has the original BIOS running 1.25 V.



That is drawing 970-1000 W.   It was drawing 1200 W or so before with all of the cards running 1.25 V.



Seems like that was the problem?

Yea I dunno whats going on.  Most of my cards (I have 13 of them) will mine with that BIOS just like they did before I flashed them.  But a few of the cards will not go over 450 KH/s (compared to 625ish KH/s) with that BIOS.


Another thing is that my two 5 card BAMT rigs will run the cards with the new BIOS in the x16 slots, but if I put a card with that BIOS in either one of the x1 slots it wont boot.  I tried jumping the presence pins and no luck.


I dunno what the deal is.  I may try another BIOS.

Um, no...I actually flashed the same BIOS to three type of cards, Sapphire/XFX/MSI and they all work the same way.

I flashed a few cards to that BIOS you linked me to.  I did it to 2 cards and they worked fine.  They mine fine and show the lower V.


But the third card I did doesn't work right.  The flash completed successfully and GPUz shows the correct new BIOS.  But when I mine with it it only get 400 KH/s.  I am using the same settings.  If I flash back to the OEM BIOS it will mine 620 KH/s.


You ever had this happen?

This is one of the rigs with flashed BIOS (the one I linked):

I got it figured out.


I flashed the BIOS on one of my Windows cards.   On Trixx when I click default on the OC panel it gives me a default V of 1068.


The BIOS you linked to that I downloaded is 1067.  But even if that's the real stock V then I dunno why my BAMT rigs default to 1.25

Yea now both rigs are doing it.  It's driving me nuts.


I tried restarting the mining and cold reboot and unplugging them and resetting CMOS and everything. I even let it run like that for like 30 mins and its just 0 load not the GPUs.

Sometimes yeah, immediately after boot, but it goes away with a mine restart. Not reboot or coldreboot, just mine restart from console or menu.
Not sure though if that is the case here.

No need to do the GPU_MAX_ALLOC thing, is executed by BAMT before it starts cgminer.

I will try once I get this other stuff figured out.   Now got dif prob.


Shut down one of the BAMT rigs to turn some stuff off in the bios.

Did it, started it up and it was mining fine.

I turn the second rig off and do it and then when I start it back up it mines but very slow and the load on the GPUs is mostly 0.  It will jump up to 99 or 100 for just a sec on one GPU but for the most part the load is 0.


I'm getting like 800 KH/s between all 5 cards obviously because there is no load being out on the GPUs.


I put the bios back to default.  I tried clear CMOS.  I even tried a fresh BAMT install on a different USB stick.


Nothing else has changed.  I know BAMT will act like its mining if it has no Internet connection but the KH/s will be 0.

It's mining a little but there is just no load being put on the GPUs .  I tried to do the GPU_MAX_ALLOC thing too.


Ever saw BAMT do this before?

Force it with -f (if I remember correctly).

Make a backup of the original in any case.

When I tried to flash to that BIOS I got an error that said "SubsystemID Mismatch".

1.09V.
Is the lowest I could find.

Do you remember what your V was with that one?

Cant say for sure which one has a lower voltage, but a good indication would be the clock speed.
Choose one with a lower clock, for example 810 / 1250.

Personally I used this one: http://www.techpowerup.com/vgabios/114183/ati-hd7950-3072-120116.html (800 / 1250) for my Sapphire cards.

Yea I have a Sapphire 21196-00-20G.

I have looked at all of the Sapphire 7950 BIOSs before.

http://www.techpowerup.com/vgabios/index.php?architecture=ATI&manufacturer=Sapphire&model=HD+7950&interface=&memType=&memSize=


Can I use any of these BIOSs?  I don't see anywhere where specific model #s are mentioned.

http://www.techpowerup.com/vgabios/index.php?architecture=ATI&manufacturer=&model=HD+7950&interface=&memType=&memSize=

I need to find me a BIOS then.

For your cards.
Other 7950 are running at 1.09V, or more.

So then 1.25 is the stock V?

You cant alter the card voltage on Linux (for 6xxx/7xxx series).
All you can do is flash another lower voltage BIOS.

To be exact, you can pull 2000W from 1000W PSU. PSUs are quite dumb, they just monitor output voltage. If it drops too much PSU shuts itself down.
Or fuse is blown
If you have more load than PSU is designed for, components generate more heat than they are designed to handle. this leads to shorter PSU lifetime (or flames if its badly designed PSU).

2000W on 1000W PSU will most definetly lead to undervoltage and safety shutdown, but you definetly can draw more than the PSU is rated.

Well I tried to set the V on my BAMT rigs.

I used the --gpu-vddc 1150 but it will not do it.


Still says the cards are running at 1.25V.

Yeah, 50W is about right.

So I just noticed another thing.


I dunno why I thought I had the rigs running the cards at 1.15V.  But I just logged into mgpumon and saw that both rigs are running at 1.25V.

I'm probably wrong but isn't the difference between 1.15V and 1.25V something like 50W per card?

Was hesitant to mess with the rigs because they have been running strong for a couple days but today on one of the rigs I put 4 of the 7950's on the 1200W PSU and I left just one 7950 on the other PSU.


I have the kill a watt hooked up and it is reading 1250-1275 W.  I dunno how long it will last or if it is gonna turn off but if it runs like this that means its drawing nearly the same amount of power from 3 7950's as with 4 7950's.   It has been running for about an hours right now.


I guess I will see how long it lasts.





But about how the two PSUs are wired together.  I ran the rigs at first with just a paperclip jumping the second PSUs on pin (green to black).  Now I have them wired together but both ways it was/is drawing the same amount of power.

That guide should be fine. The black wires (ground) are tied together. I prefer to use a pin/small screwdriver to remove pins I don't want, rather than cut them all (I used that technique to convert an old Dell PSU to ATX).

I took a second look at that guide. For some reason, the have the Power Good signal (pin 8 ) tied to ground (pin 7). Power good is 5V, ground is 0V. Assuming a source resistance of 0.1 Ohms, that may explain 50 Watts of power draw. I would cut that loop. If some power draw is required, I would use a 10kΩ resistor.

Whoa.  I don't understand any of that.


I do have the PSUs wired together correctly now. (I think)


I used this guide.

http://www.burningissues.net/how_to/power/adaptor.htm

I don't think the Kill-a-watt is wrong. Something is probably wrong with your dual-PSU setup.

I suspect the grounds should be tied together (especially if you are drawing from two branch circuits), but that may cause ground loops. The power supply box may have a hole threaded for a ground screw. You should not be continuously drawing more than 12 Amps from a 15Amp 120Volt circuit anyway (load is supposed to be de-rated to 80%).

If there is a voltage difference between the two supplies, you may be getting enough current flow to explain the results described. V=IR -> R =V/I -> (12V)/(1200W) -- (P=IV -> I=P/V) -> (12V)(12V)/(1200W) = 0.12 Ohms
Power supply voltages are supposed to be within 5%: 12V x 5%= 0.6V
Current flow if power supplies mis-match: V=IR -> I=V/R -> (0.6V)/(0.12 Ohms)= 5 Amps
Power = IV -> (5A)(0.6V)= 3Watts.

Hmm, never mind. That does not appear to explain it.
 

I think I've weighed in on this before, but I will do so again. Dual PSUs are almost always bad juju, from what I've read of peoples experiences.

If you're worried about blowing your PSU, try the following, 4x7950 off a single PSU. 250Wx4 cards + 200W overhead for your Mobo + fans + CPU + whatever should be plenty. It's a silverstone which is typically a good quality PSU, so it should be able to run at peak for extended periods of time, just don't go crazy and OC like a madman for this phase.

I don't want to read back to what exact model you have, but I believe you said 80Plus Gold. So assuming you're hitting exactly 1200, which feels unlikely but possible, you'll be running 87% efficient, so you should see ~1380W on your kllawatts from the wall.

If so, it is as I suspected, your dual PSU set up is being a boner and causing you headaches. If you see more than 1380W from the wall, I'm a bad man potentially causing you to murder your system, shutdown ASAP (assuming nothing faulty you shouldn't be in this scenario). If you see less than 1380W from the wall, as I mentioned earlier you probably have even more headroom than you thought.

Somehow my Athlon 145 +misc uses ~180W, which is why I don't expect you'd use much more than that.

just a thought...try pulling one card out your 3card puter n put it in the 2 card system...see if the power jumps up...i dunno if you tryed that...good luck

I dunno.  I tried two different 1200W PSUs and I tried two different 5 x 7950 BAMT rigs.


I could start pulling cards to see if one is consuming too much power but I have two separate rigs each with they're own 5 cards.  So both rigs would have to have a card or two with big power problems which seems very unlikely to me.  Unless I'm wrong.

Those 7950s should only pull 200-225W each, so your second PSU looks just about dead on. Your main PSU should pull <700W for the GPUs, so I can't figure out how you're pulling ~500W for your motherboard and CPU and nothing else.

So I did some more testing.

I have another rig identical to the one we are talking about here.  Only difference is it has the ASRock 990 EXE4 instead of the 970 EXE4.  Everything else is the same.


So I switched this rig over to BAMT yesterday and I hooked up one of the 1200W Silverstones as the main PSU.  Running 3 cards and the rest of the system.

Same results 1150-1200 watts.



I tried hooking up a Cooler Master 1200W gold PSU as the main PSU and it actually reads more W.  It reads 1200-1250W on my kill a watt.


If you look at this thread https://bitcointalksearch.org/topic/rig-turns-off-after-15minutes-208299 he is getting about the same results.


Only thing I dont get is that the second PSU which is only running 2 7950's and a case fan only pulls 450W.


So to summarize I have 2 seperate rigs with nearly identical hardware which both draw 1150-1250 W on the main PSU running 3 7950's and the rest of the system (no matter using Cooler Master or Silverstone) but which only draw 450 W on the second PSU running 2 7950's.

Only other thing I can think of then, is on your computer system, remove one GPU at a time. Unplug one graphics card so you are only running two, and see how many watts.

Then remove another GPU, so you are only running one, and see again.

Can also compare watts with using riser/molex, versus card plugged into motherboard directly and see.

Thats another thing I was asking before.  Should I hook the two PSUs together instead of the paperclip?

Would that make a difference?  Or is that just so they turn on together?

That is how I have it hooked up right now.  I do NOT have them hooked together, just a paperclip in the second one like you said.



I switched them around and its the same thing.  The one with the system and 3 cards hooked up is drawing like 1200W.



But here is something else I found.  When I was swapping them over I noticed something I forgot to list.  I forgot I also have 2 molex's hooked up to the main PSU from the riser cables.  So thats 75Wx2 = 150W right?


So  250 X 3 =750, + 150 from the riser cables = 900  + whatever power the system is drawing which is ?  I dunno what like 150W.  If so thats 1050W right?  Or am I wrong?

So you've got 2 PSUs:

PSU1 has the Motherboard & CPU, 3 GPUs, and it's pulling ~1300W?
PSU2 has 2 GPUs and it's pulling ~500W?

1800W is WAY too much for a 5 GPU system. Each card should pull ~250W, so PSU2 looks about right. However, PSU1 should only be running ~800-900W or so, not 1300W.


Try not connecting the two together, and just shoving a paperclip between the green and black wires on PSU2 to start it without the computer. Or if you've already cut off the green wire, run it right into the ground (on the same PSU, not the other one).

I guess I would switch the two PSUs to see what happens. Since they are both 1200W, you shuold have no problems.

The one that is just running 2 cards and a fan ---> hook it up to your computer setup
The one hooked up to your computer --> connect to just the 2 cards and fan

Curious to see, but it could very well be a bad PSU.

So I tested the kill a watt.  It works fine.  I hooked a hair dryer to it that says it is 1575W and when I turned it on hi it was pulling 1500-1520W.  I hooked a 100W light bulb lamp up to it and it read 95W.



So this is where it gets wierd.  I think maybe I have a bad PSU.  Instead of hooking the kill a watt back up to the same PSU that is running the system and 3 GPUs, I hooked it up to the PSU that is running the 2 GPUs.

This PSU is only running 2 GPUs and 1 case fan.  thats it.  The rig is mining right now and it is reading 490W.




So how can this be?  Does this mean the PSU that was reading almost 1200 W on three cards is bad?

Oh yea and I am not doing anything with the CPU.  Just mining LTC with the GPUs.

This is the system.


ASRock 970 EXE4
Athlon II 270
8GB DDR3 (4 x 2GB)
1200W PSU running 3 7950s  Another 1200W at the moment is powering the other 2 7950s.
No HDD just a USB stick with BAMT on it.
The W is being measured with just the PSU plugged into it.



I am about to test the meter.  I will report back what I find in a few mins.

Testing the KAW with a known load (bulbs) that someone above suggested is a good idea.

Other questions: give us full details of your system hardware (motherboard, CPU, how many SSD/HDD, etc). Does the wattage also reflect a monitor that you have hooked up? I presume not since you are plugging the PSU straight into the KAW right?

Also, are you using the CPU for anything (CPU mining, etc)?

As others have said, you should not be pulling that much wattage with just 3x 7950s.

Off topic: I used to have a high school teacher called Mrs. Watt. What makes it even better is that she was an IT teacher

Can it be the way I have the dual PSU setup?


All I did was short the green wire to ground on the ATX connector on the second PSU.



I saw another guide that showed splicing the green wires from both PSU ATX connectors and also both grounds.  It says to do this and also to splice pins 7 & 8 together which is the power ok and ground.


I don't see how this at all could make the cards draw this much power.  But I dunno.


I will test the kill a watt tom and report back.

One way to check for a bad kill-a-watt is to plug something into it which has a defined wattage (hairdryer, lightbulb, etc).  If nothing else a multi-plug extension cord, and as many lamps w/ 120W bulbs as you can find makes a good test load. Make sure to find out the max wattage the k-a-w can handle before you melt it trying to plug in an arc welder.

1141Watts with only 3 cards? Ya, 3x 7950s should run on less than 800Watts. You should be able to run 5 7950s for BTC mining with lower memory clocks with no problems.

If you've got 2 of those 1200W PSUs, try swapping them? Maybe it's a bad Kill-a-watt?

Yea.  I have these PC Power & Cooling 500W single rail PSUs that I was planning on running my 5 card off of and I cant even run 1 card off of those.


But yea the above pic is just 3 cards.  I have the other two cards running off of another identical 1200W PSU for the time being.  My original plan was to run 4 off of one 1200W PSU and the other card off of one of the 500W PSUs.

And this is no overclock on these 3 cards.

But I cant get it to run like that because the cards are taking so much power.

Are you sure you are reading WATTS and not VA (volt-amps) off your meter?

I have 3 7970, stock speeds, and I pull 875W according to my Kill-A-Watt with a Gold rated 1200W PSU.

Yea After diong some more research I think these 7950s should not be using more than 300W.  Alot of people are saying 200W.


I do have the kill a watt plugged into the surge protector.  Does this make a difference?  Should I plug the kill a watt directly into the wall then plug the surge protector into it?

What do you mean my Silverstone can handle it?  It cant handle 5 GPUs.  According to this kill a watt this thing is maxed out on 3 GPUs.  And I didnt know you have to bridge the PSUs.  I just thought you had to rig the ATX connector so ithe second GPU would turn on.

never ever use SATA adapters.

You probably screwed up the connection in bridging the PSUs. Since your single PSU can handle it, why not go buy some SATA/molex adapters and just run everything off the silverstone?

no i am running a 5 card rig but I have only 3 cards running off of this PSU.


The other two cards are ru nning off of a different PSU.



I have read what others are drawing running 7950s and this seems very very high.  i have read a few people running 3 cards off of 800W PSUs.   these 7950s should only draw about 200W percard when mining right?

It certainly is possible.  PSU are rated for DC OUTPUT power.  Depending on how efficient your PSU is (most modern PSU are 80% to 90% efficient at 100% load) the AC input load will be somewhat higher.

Yep that's normal.

1,200W is the amount of wattage the PSU can supply to the computer.

An 80Plus Gold PSU will be ~87% efficient at 100% load, according to the specification.

This means that for ever 1 watt you pull from the wall (which is what your Kill-A-watt is measuring), you will supply 0.87W to the computer.

A 1200W PSU supplying 1,200W to the computer will pull ~1,380W (1200/0.87) from the wall.

If you're drawing 1,300W, your 5 card rig is really only drawing 1,131W (1300*0.87).

I also have powertune to 20.

I am running 1000/1225 and stock V.  As far as I know stock V.  I am using BAMT and use cgminer config file to OC the cards.  Ill look againbut I dont think I have anything specified for the V.  So I assume its stock.  I do have powertune at 20.

What voltage and clocks are you running? I have an i5 760 rig with one 7950, and 2 monitors hooked up to my kill a watt. If I run it at 1.187V core and 1.625V mem I draw about 400W with the monitors on, and around 340W when they are asleep. This is total power consumption though, so the card itself is probably only using like 220-240W.   

Yes. The 1200w is the output rating, and the 1290w is the input measurement. Due to conversion loss, the 1290w input is roughly 1120w output (1290 x .87). Well under the 1200w output rating.

I have a 5 card rig.  I am running 3 7950s off of a Silverstone 1200W gold PSU.  And 2 7950s off of another 1200W PSU.





I hooked up my Kill a Watt and it says I am pulling 1260-1290 W off of the one 1200W PSU that is running the 3 7950's.



Is this possible?