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Originally Posted by Groth
The whole reason they give the option of sensing voltages at/near the silicon is because the copper traces on the board have a big tempco, and you want your V-reg system to supply the same voltage at the silicon regardless of mobo temperature.
Ain't too useful, unless you plan to actively cool the mobo to a specific temperature, or you have a scheme to measure the trace resistance vs. a temperature map, or...
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No Groth, check your math, check some MB design guides. Temco of MB wiring is low enough to fall into cpu tolerance range. Its not compensated like that. Most (if not all) MBs don't even use these pins to regulate Vcore. Intel reference designs advise to take feedback from specific VCore pin under the socket, not from these Vsense pins. Resistence of power path is in 3 milliOhm range, impedance of P4 Core is in 30mOhm range. The voltage drop due to tempco is under millivolt or few.. totally nonissue.
For some reason they do not want to use Vsense as Vreg feedback signal. It must be good reason, though I don't know it. Perhaps to avoid oscillation issues.
These pins allow one to measure combined resistence through the socket for power path, which is specified with quite strict tolerance. But they are meant to measure precise voltage across core. Maybe they are used to report the Vcore by chips like Winbond.
Anyway, even though AMD has no Vsense pins, the principle is still sound - take any pin on socket for both Vcc and Vss, measure voltage across it, and measure voltage across Vss path back to Vreg. Knowing resistence of power path to Vreg, you can arrive to cpu power. By any means, precision of measuring electrical signals wins over measuring temperatures directly any time.