4 ms·
"Stepping suddenly from lower to higher power, such as when a cache is missed or a new core turns on, causes a large current step and parasitic package/board in
by Jeema101 7y ago
"Stepping suddenly from lower to higher power, such as when a cache is missed or a new core turns on, causes a large current step and parasitic package/board inductance, which means a correspondingly large voltage drop."
Wouldn't one solution be to use linear voltage regulators instead of switched mode? Or some combination of switched mode and linear?
I am aware linear regulators are much less efficient, but my understanding is that they respond to transients much better.
- sjburt 7y agoIt’s not an issue of the supply, it’s an issue of the current paths inside the chip or on the motherboard. With smaller features and more complicated routing there is more inductance.
- deleted 7y ago[deleted]
- myself248 7y agoBy the time the transient reaches the voltage regulators, it's old news. We're talking about a base clock in the multiple GHz, which means the edges of power steps have harmonics in the tens of GHz, which means wavelengths on the order of millimeters. When they talk about package and board inductance, think of it as meaning that the board itself is a transmission line and its characteristic impedance is limiting the risetime of the current waveform. No amount of regulator response can overcome that.