http://www.calgaryfieros.com/OSGdocs/ECM-hacking.html http://www.calgaryfieros.com/OSGdocs/ECM-hacking.html The GM engineers used a similar approach: > The EC

http://www.calgaryfieros.com/OSGdocs/ECM-hacking.html http://www.calgaryfieros.com/OSGdocs/ECM-hacking.html The GM engineers used a similar approach: > The ECM hardware generates a periodic interrupt at 160 Hz. (Where have we seen that number before?) The entire ECM program operates off of this one interrupt. Except for some initialization code, there is no non-interrupt level code. In fact, the interrupt service routine never returns, it simply cleans the return address off the stack and waits for the next interrupt. There are no other interrupts in the ECM. This means that fully autonomous hardware generates all the high speed signals like the fuel injector and ignition pulses. > At each tick of the 160 Hz, various tasks are performed. Some are done every tick. Others only on just odd or just even ticks. There are also 16 tasks, one of which is performed each tick. Every tenth of a second, all 16 tasks will have been completed. In general, this means that the ECM cannot adjust engine performance faster than 10 times a second. Perhaps this explains the engine surging at low rpm that many list members have complained about.