On Tue, 2 Jun 2026 15:06:20 -0400 Dan Ritter <[email protected]> wrote:
> David Christensen wrote: > > On 6/2/26 07:02, Stefan Monnier wrote: > > > > I've seen too many hard-to-diagnose problems that disappeared > > > > after replacing a sketchy PSU. Random hangs and crashes, hard > > > > drive errors, video noise, hang on reboot, etc. I no longer > > > > try to go cheap when choosing a PSU for builds. > > > > > > Yeah, I'm actually surprised the hardware hasn't caught on > > > accordingly: while it's now standard for chips to monitor their > > > temperature (and adjust their power consumption if it gets too > > > high), I still haven't seen anything comparable that would detect > > > and report when the input voltage goes out-of-range (and maybe > > > also take steps to reduce the instantaneous power consumption?). > > > > > https://en.wikipedia.org/wiki/Lm_sensors > > > > lm_sensors (Linux-monitoring sensors) is a free open-source > > software-tool for Linux that provides tools and drivers for > > monitoring temperatures, voltage, humidity, and fans. It can also > > detect chassis intrusions. > > Almost all of those sensors are on the motherboard or on > attached cards; you'll frequently get to see voltages from the > CPU, but hardly ever does a power supply tell you about its > load. > They are also going to be polled, and will return the voltage they find at polling time. What they won't tell you is what various ripple voltages are, both the initial rectified mains at 100/120Hz and the residual switching frequencies of the various step-down regulators. Under some combination of conditions, including temperature, the combinations of ripple may allow a regulator output to drop out of spec for a microsecond, more than enough to corrupt a signal on e.g. a SATA line. Further, this may only happen once a week or so. Increasing ripple voltage is what happens when smoothing capacitor electrolytes dry out, which they will eventually do with age. Einstein allegedly said: "Insanity is doing the same thing over and over again and expecting different results" He had obviously never encountered the Intermittent Fault. -- Joe
