Reply 60 of 382, by PCBONEZ
wrote:wrote:As overclockers can tell you undervolted parts use less watts.
Here you are wrong. A video card is not a simple ohmic power consumer at the 12V, but includes at least one switching regulator. When the input voltage gets lower the regulator increases the input current to be able to supply the same output voltage and current. This can go on until the input current becomes too high for the switching regulator and the protection kicks in.
That might be true for some parts of the card but not all of it.
There are ~20 amps of 3.3v in AGP that go directly to chips as Vcc and an additional ~2 amps of 1.5v that also does not go through a switching regulator.
There are ~2 amps of 5v that may or may not go through a switching regulator.
So what you are saying does not apply for up to 33 watts of the card's power.
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The below pic is a screen shot out of the APG 3.0 Specification. Happened to be working on it for something else.
It shows the power through the slot. The blue is my notes.
Also many of the smaller VRs on mobos and add-in cards are LDO regulators which are not switchers and don't have PWM controllers or other driver chips.
They are often in packages that look just like MOSFETs but they don't work the same way.
It would be typical for the input to those to be 5v or 12v so some or all of the 5v and 12v may not even be going to switching regulators.
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