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.