> On Sun, 04 Jun 2006, Hans de Goede wrote: > > I think they are just seeing if it gives any "ticks" at all, so it won't > > detect a 2 wire fan even if connected to one if its headers. > > Two-wire fans can be detected just as well as three-wire ones, if you > measure current draw :) In fact, some chips (like the lm75) can actually > COUNT ticks on two-wire fans by measuring spikes in the current draw... Definitely not the LM75, as it is a temperature-only sensor chip. But I remember reading datasheets mentioning tick count on 2-wires fans, indeed. Strangely enough, some vendors are doing the opposite and propose 4-wire fans, the idea being that tick counts tend to be lost when fan speed control is in use on 3-wire fans. > If you detect fan presence using ticks, you will never detect a stuck fan on > startup, which is *dangerous* as it could cause the software inhibit an > alarm on that fan. Indeed - which is why I don't want us to emulate it in software. -- Jean Delvare
