marsheng,
It isn't as simple as that.
A microsquirt will typically draw well under an amp of current. But it sinks quite a bit more from the injectors, idle air valve and other controlled devices (like LED, relays, etc.). See this page:
http://www.useasydocs.com/details/wire.htm for details of the fuses you need.
The power should be standard automotive 12V. That is, between ~10 and ~15 volts. Less than 8 volts will cause issues with the controller (and many other components on the vehicle). More than 17 Volts could cause trouble too.
The theoretical rpm limit is 65535 rpm, and this can certainly be achieved and sustained on the bench in testing. However, it does depend to some degree on the input signal used to determine the engine speed. For example, the code would probably run smoother and with increased accuracy on a 36-1 crank wheel compared a 300-1 crank wheel.
Temperature sensors are variable resistors (negative temperature coefficient thermistors), and the microsquirt supplies the voltage to them (using the thermistor as one leg of a voltage divider). The throttle position sensor's output must not exceed 5 Volts. Microsquirt provides a 5V source (Vref) to use with the TPS.
The number of cylinders that can be supported depends mostly on the input options (you need at least one physical 'tach event' per spark event) and the current flow and flyback spikes for the injectors. These have to be determined on an individual basis. Generally 1 to 12 cylinders isn't a problem for the code, and up to 16 cylinders is possible, I believe.
Lance.