On 10/1/2022 9:07 PM, Skybuck Flying wrote:
> https://tweakers.net/pricewatch/compare/1859276;1849718;1859272;1866988;1859274;1867042;1867046;1867140;1867026;1867028/
>
> Gigabyte AORUS X670 ELITE AX
>
> Only 70A while other motherboards have much more.
>
> So is this a weak/bad motherboard ? Seems so.
>
> I think more ampere is better, because then it can handle bigger processors/more load ?
> I am correct, I am not an electronics person.
>
> Bye,
> Skybuck.

Up to a certain level, the amperes of rating are needed
for basic ohms-law reasons. A 2 amp transistor, would not
even be able to budge the load, and all the power would
be dissipated by the transistor. The magic smoke would come out.

But, above a certain level, the "rating" is not used. Instead,
it makes the circuit run cooler. A lower RdsOn means lower power
dissipation in the saturated ON state.

The difference between 70A and 110A, would be that the latter runs
a bit cooler.

But by doing that, it is not entirely arbitrary. The gate of the
MOSFET has gate capacitance. It can be 3000pF, which is a huge load
to drive at a high frequency. This is why the regulator chip is
surrounded by buffer chips. It is the buffer chips, which drive
the 3000pF load. The difference between the 70A transistor and
the 110A transistor, could be the kind of buffer chip used to
drive it. The transistor runs cool, the buffer chip runs hotter.

Some things designers do, it's all about "cheapness".

At other times, it's a complicated series of tradeoffs,
trying to balance the circuit, so no one part of the
circuit is burning hot.

One of the reasons they can even do these things, is the
power limiter the Vcore has now. In the old days, a phase
could only run luke warm, and that was because if it got
hot, it would go into "runaway". And cook. If that happens
on these fancy motherboards, as soon as the power rises
above a certain number of amps, the circuit can shut off.
And that allows a lot more thermal headroom in the design.
That is why my motherboard VCore can rise to 65C, without an issue.
It's the power limiter that made it possible. That also allows
a less-capable transistor, up to a point.

Paul