## Weak Power-Supply

The current computer ‘Phoenix‘ (I own several computers) has suffered from a string of malfunctions in the past, which I had trouble diagnosing the cause of.

I think I’ve found the problem: Its power-supply is weak in some way, which can also lead to low-voltage conditions that it subjects the high-speed electronics to. When high-speed logic circuits are fed low supply-voltages, the computer can spontaneously crash.

The reader may wonder how I know this.

When I’ve left the computer idling and come back to it, thus entering my password to dismiss the screen-saver, the case-fan speed seems to be stable around 3,500 RPM. But as soon as I fire up my Web-browser, the CPU usage goes from low-usage to nearly-100% usage for less than a minute, and as soon as that happens, the case-fan speed becomes unstable, sometimes resulting in a reading of ~40 RPM, which means that ‘The fan has stopped spinning.’ Then, as soon as I allow CPU usage to go below 5% again, the case-fan speed sometimes stabilizes again, within the same sitting.

Well there is no valid logic by which the motherboard would signal for the fan to stop spinning, or to slow down, at the moment the CPU usage is high. And so the only other explanation I can think of, is that the CPU – and possibly other circuits in the box – are drawing more current, and that this is causing a temporary dip in supply-voltage, just enough for the recently-installed fan to stop spinning.

But then, such a weakness also makes this computer more susceptible to such phenomena as brown-outs. Even though my eyes can see power-fluctuations that take place within a fraction of a second, I cannot see a low-voltage condition in the A/C power we are fed, if that low-voltage condition has set in over a period of minutes.

I might start looking for a new power-supply for this old box, rather than a new case-fan.

## Power Fluctuations, Downtime

I take the unusual step of hosting my Web-site, and this blog, on my personal computer at home. If the reader has questions about how this is possible, I gave a brief explanation here.

One of the unfortunate facts which this implies, is that my site availability is only as good as the reliability of my personal computer. People who have their sites hosted more conventionally on professional services, are also paying to have professionals avoid downtime.

Today we are having extreme weather on the Island Of Montreal. The maximum daytime temperature is expected at 32⁰C, and we are having continuous, powerful wind-gusts.

What this has done is cause brief, momentary power-fluctuations to take place, that are long enough to cause this hosting computer (‘Phoenix’) to go down, but which are short enough, that the supply-capacitor charge on most of my other systems – including several other computers – allows those to keep running, as though no fluctuation had ever taken place.

In fact, this has taken place in such a way, that my IP address never actually changed. But, my Web-server ‘Phoenix’ did go down, not once but twice so far, taking my Web-site down with it.

This started happening around 12h00 today, but is expected to continue throughout the afternoon. The extreme weather is in fact expected to break, when severe Thunderstorms put an end to the high temperatures.

Also, because this type of a reboot causes my server-side caching-daemon ‘memcached‘ to restart, it means that the speed with which the most-frequently-requested pages are served, will be slow for some time to come.

I apologize to the reader for this, but it is just an automatic hazard that follows, when we host our Web-site on our home computers.

Dirk

(Edit: )

This type of a ‘power fluctuation’ can be described more precisely. One seemed to take place which I did not witness, while one took place which I did.

I’d call that one a ‘voltage drop-out, that lasted somewhere between 1/10 and 1/5 second’. There seemed to be no period of partial voltage; the lights just went dark for that fraction of a second.