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Topic: Is my Kill a Watt wrong? says pulling almost 1300W from 1200 W PSU? - page 2. (Read 7816 times)

full member
Activity: 168
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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?
hero member
Activity: 700
Merit: 500
This is one of the rigs with flashed BIOS (the one I linked):



full member
Activity: 168
Merit: 100
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
full member
Activity: 168
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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.
hero member
Activity: 700
Merit: 500
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.
full member
Activity: 168
Merit: 100
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?
hero member
Activity: 700
Merit: 500
Force it with -f (if I remember correctly).

Make a backup of the original in any case.
full member
Activity: 168
Merit: 100
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.


When I tried to flash to that BIOS I got an error that said "SubsystemID Mismatch".
hero member
Activity: 700
Merit: 500
1.09V.
Is the lowest I could find.
full member
Activity: 168
Merit: 100
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.


Do you remember what your V was with that one?
hero member
Activity: 700
Merit: 500
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.
full member
Activity: 168
Merit: 100
I need to find me a BIOS then.


hero member
Activity: 700
Merit: 500
So then 1.25 is the stock V?



For your cards.
Other 7950 are running at 1.09V, or more.
full member
Activity: 168
Merit: 100
So then 1.25 is the stock V?

hero member
Activity: 700
Merit: 500
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.


You cant alter the card voltage on Linux (for 6xxx/7xxx series).
All you can do is flash another lower voltage BIOS.
full member
Activity: 168
Merit: 100
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 Wink
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.
full member
Activity: 168
Merit: 100
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.
full member
Activity: 142
Merit: 100
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?

Yeah, 50W is about right.
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