Topic: 7970 results with a kill-a-watt (Read 3519 times)

There's asic numbers on slide 5 that  indicate that its half and half at 65nm and the W/mm^2 numbers shows that the asic is near full utilization...

I am not sure what your suggestion of comparing clock frequency will do. If you set it so low, then static power consumption dominates. So when it goes back up to normal clock it would seem like dynamic power usage has super-linear influence at higher clock frequency, since a clock edge is now a significant part of a clock period and eating away as the time the transistor spends at static . The only way to accurately tell the static and dynamic power usage is to clock gate the device.

That might be true with an SoC that has very low utilization, but a GPU that's mining will be near 100% utilization. If you think static power dominates dynamic below 65nm, fix the voltage of one of your 7970s at 975mV and run some mining software with 200core 200mem, and then with 1000core/200mem and report the results of the power draw for just the card.

Dynamic power usage is indeed P = C * Vcc^2 * f, but it does not make up the majority of power consumed by devices on a high-performance 28 nm process such as the one employed on a 7970.

In fact, static leakage currents now dominate the power usage of modern ICs circa 65nm (note the log scale on the left of the 2nd slide) and is exactly the reason why we need to power-gate most of the chips when they are not in use (as opposed to clock-gating, which we did before and would be a viable solution if dynamic power dominated the power consumption).

Static power consumption is related to an exponential, but the dynamic power power usage is just related to f*Vcc^2 and makes up most of the power consumed by a GPU. Power might not scale exactly with the square of voltage, but it's a lot close the the SDE.

To the OP, I just used a PCIe riser and cut the 12V lines to the board and soldered it to a molex plug.
http://en.wikipedia.org/wiki/PCI_Express#Pinout
There might be some power drawn by the 3v3 lines, but it would be insignificant. You should be able to isolate the GPU pretty easily to test it.

81%

What is the ASIC Quality % of the card that you tested to achieve the numbers above ?

He didn't lower clock. I'm curious how low voltage can be set even sacrifying core clock (performance).

If you'd read his chart, it looks like he's already done that! .918 is stable at 925, but .900 isn't.

OP, can you measure how low can you go with voltage even dropping core clock? Where is limit with undervolting?
My 6950 will no go lower than 0.987V no matter what core clock I set...

Oh. I missed that part With that and the assumed thing that he isnt measuring power from PCI-E is interesting.. so looks like  it won't fit in just right unless the OP is powering the 12v, 5v, and 3.3v lines from the seasonic too, leaving only data lanes and PCI-E critical pins attached to the motherboard.

Power is not proportional to the square of voltage. According to the Shockley Diode Equation, Current is exponentially proportional to the Voltage, so the power is actually something like P ~ V*e^cV.

Where c is some constant governed by device physics and temperature.



OP only has GPU plugged into the PSU he is measuring. Which is a bit skewed also due to not measuring power being drawn from PCI-E slot.

Interesting numbers, but unless my math is wrong, something weird is happening here..

You claim 128 watts for 7970 @ 925MHz and 0.918v, and 139w @ 950MHz and 0.937v for the whole system. Lets assume the 11 watt power increase is from the graphics card alone, since nothing else changed.
Power consumption can be guessed by TDP * (current gpu volts / stock GPU volts)^2 * (current gpu speed / stock gpu speed), but we can use the same formula to get the relative power increase from one situation to another. So...

(new volts / old volts)^2 * (new speed / old speed) = change in power
(0.937v / 0.918v)^2 * (950/925) = 1.06998 or 6.998% increase in power.

Lets assume 11 watts was the 6.998% increase in graphics card power draw, and want to find how much power the card was actually drawing instead of the whole system. We'll try to find the power draw of the card running in the first scenario (925 core, 0.918v)

x = relative change in power, or 6.998% or 0.06998
y = absolute change in power, or 11 watts
z = power the card should be drawing.

Actual power = Absolute change / relative change
z = 11/0.06998
z = 157 watts

But what is this? In this scenario, the owner listed that card to only be drawing 128 watts for the ENTIRE SYSTEM, but by my calculations, the card should be drawing 157 watts ALONE.

What is going on here? Is my math wrong? Is the power supply somehow creating power out of nowhere? Are 7970's somehow ignoring the laws of physics?

Please, someone explain. I am baffled.

cgminer.... Plus you said it wasn't possible anyways. Just saying it is possible.

Show me a way to do this automatically please. People who mine want as much automation as possible.


It does matter if you're going to matter card consumption by delta.... as I've stated time and again.

It doesn't matter what your idle usage is.. you're mining bitcoins.. the card shouldn't be idle.

Yes you can... Just put a load on the cards when changing the clocks.

That's with ULPS on. Multi-card miners can't run with ULPS on and still overclock the cards.

You have something wrong if your card is drawing 40 watts idle. They should be <15 watts idle with the screen on and they drop to <5 watts idle with the screen off.

My numbers with three 7970 clocked to 925/150/860mV

hashing away with a speed of 1650Mhash/s

drawing 440W from the wall. That will drop somwhere around 420W when it gets cooler during the night. This is for the whole system which is not that efficient with a Phenom CPU and HDD.

Measuring delta doesnt measure the MH/W of the card accurately either. If you measure idle power and then add to delta, that would give you the true power in order to figure out the card MH/W. The idle power of these cards aren't exactly negligible compared to the load power. Mine sucks up ~40 watts idle.

Also, related thread on the subject: https://bitcointalksearch.org/topic/3x7970-mining-results-57410