Furnace controller product - optimized energy consumption in a steel recycling furnace. Customer reported the furnace got 'stuck' every couple of hours, the electrodes quit moving so it continued to burn electricity (megawatts!) but wasn't melting anything.<p>Turned out it was the 'power saving' setting on the PC. To save a couple of watts it slowed down the CPU, and screwed up a furnace that burned megawatts. Probably wasted more electricity in a day than the 'power save' feature saved in the whole US for a year.
Craziest to me is The Bug by Ellen Ullman.<p>Personal craziest was an Oracle performance problem on Windows NT in the 90s. Slow as hell. Going to the server, logging in, checking everything: Blazing fast. Back at the desk, slow as hell. Problem was the GL tube screen blanker with software rendering :-)
My craziest bug was a Java clock issue. If you had some specific model of motherboard, calling System.getCurrentTimeMillis() repetitively could actually make your system clock run faster. I mean, actually CHANGE the system clock. For real. Like 10% faster. That led to veeeeery interesting issues related to timing on the game I was working on, and of course it me took days before I would even think that my problems could be caused by the time actually running faster on different machines.
Wow, already down, that was a fast one ;)<p>Cached version <a href="http://webcache.googleusercontent.com/search?q=cache:http://timetobleed.com/digging-out-the-craziest-bug-you-never-heard-about-from-2008-a-linux-threading-regression/" rel="nofollow">http://webcache.googleusercontent.com/search?q=cache:http://...</a>
Oe the site comes back up the author has a phenomenal analysis of the perf events local root exploit from over the summer. If you're interested in exploit development or just security bugs in the kernel his analysis is great. He takes the time to explain things at a level that even the worst cs student could understand.