Spec-Check :)

You have to know how to interpret those figures. One of those figures is "magic" and someone needs to translate it into English.

The figure I quoted, is extracted from here.

and is the same 29W as your Geforce (Nvidia controlled) website. So this value, is the value provided by the manufacturer.

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Power Consumption up to 75W no additional PCIe power required

Now, that 75W value is the limit of the PCI Express motherboard connector. In other words, if you draw 76W with a high end video card, the edge connector (in theory) would burn up. The number is based on the number of contacts in the PCI Express slot, in the power delivery section of the connector.

A video card, with no AUX connector on the end of the card, is limited to using 75W, as provided by that connector.

The video card in question, the GT520, *actually* draws 29W, well below the 75W limit.

So Asus is saying, "we don't know the real actual power, but our marketing people can tell you the power must be less than 75W, because there is no AUX connector on the end of the card".

So the power number for the card, remains at the 29W value I quoted.

As an engineer, I always do "sanity check" on power calculations. Say a power calculation gave 1000W dissipation, on a device that fit in the palm of my hand. Common sense tells you the object would be "incandescent" if it dissipated 1000W. So any time you receive conflicting information, look at the heatsink. "Does that heatsink handle 29W ?" "Does that heatsink handle 75W ?". If you look at the heatsink, the physical size and surface area and fan size and fan speed, can give a hint as to actual power.

I'm willing to bet, if Xbitlabs.com measured the power for the GT 520, they would find a value of *less* than

29W. They equipped a couple motherboards with current measurement shunts, so that they could measure the current flow in the edge connector. Measuring one card is not statistically significant (does not establish the mean value), but it can shine some light on the absurd manufacturer number. The manufacturer numbers (29W) are normally, too high.

Modern cards have things like "power limiter" in the design, to cap the tails of the 3sigma power distribution. At one time, the video card you bought, could have a higher power dissipation than the one I bought. And this is statistical variation. (This is also affected by the OEM video card manufacturer overclock setting and VCore choice for stability.) But with some of the modern designs they have power limiters, if you run Furmark, the card "throttles" itself, if you attempt to draw too much power. So rather than having a fixed computation rate of 512 shaders at 1000MHz, the computing rate is fixed by when the power regulator says "you're drawing too much power" and the clock rate drops in response.

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GT 520 = 29W

Still true.

Until Xbitlabs measures it, and gives us an even *lower* number.

Paul