Daniel_R : I unplugged the power connector from the motherboard, turned the power supply on and off, and plugged the power connector back on.There is only one way to connect it so you can not create fireworks. Result : computer still boots up but still without Fast Mem ... :pissed:
Theoretical all my spare Simms can be faulty, not very likely, but it is possible. So I took a working Simm from my third Amiga4000 that has 16Mb Fast Ram, and plugged such a working module into an A4000 that refuses to use Fast Ram.Result : still no Fast Mem ... :pissed: Means that the problem is not the Simm module(s) but the computer itself ...
I tried to set the Rom Speed from 200 to 160 by moving a jumper next to the IDE port ... no difference ...
Anybody any other cool ideas that I don´t know

(to be honest, I don´t know that much of A4000´s)