On Wed, 10 Dec 2003 07:11:31 +0100, Markus Bernauer
Is it really necessary to bootstrap the system as fast as possible or
do you only need to be ready to operate as soon as possible after the
power is applied ?
In the old core memory days, the power fail interrupt simply stored
the volatile internal CPU and peripheral registers into the
non-volatile stack in the core. At power on, these registers were
loaded back core and the system was ready to run in a few machine
instructions after power up as if nothing had happened.
Modern implementations could use battery powered RAM or various
hibernation tricks such as storing the contents of the RAM and CPU
registers into a flash card. Of course the power supply must be able
to maintain the voltages for some time between the power fail
interrupt and actual disappearing of the power in order to be able to
save the memory contents.
Using some hibernation tricks to suspend the processing is usually
much faster than making a full bootstrap sequence. So in principle, a
system needs to be bootstrapped only once, but after that, power
failures and even component replacement can be done without a full
reboot if the system has been designed that way.