|Re: [hatari-devel] Bootup differences|
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Le 16/06/2013 22:03, Eero Tamminen a écrit :
I'm seeing differences in profiles of successive, identical
EmuTOS boots with Hatari. Profile is from Hatari start until
EmuTOS desktop first calls evnt_multi().
I was assuming that host clock could through RTC affect when interrupts
start ticking, but disabling that didn't help.
Nicolas, what else could be causing differences between successive
(This isn't a new problem, it happens also with e.g. Hatari v1.6.2.)
well, those differences are rather small in the end, and are certainly
higher on a real STF where the boot state is not necessarily known,
because some components like MFP or ACIA use their own clock, and this
clock is not synchronised to the 68000's one.
That's why when the CPU needs to "talk" to the ACIA for example, a use
of the E clock is required to synchronise both sides. This E clock has a
fixed frequency (1/10 th of the CPU freq), but its phase is not known at
start, this means that the same instruction at the same time will
sometimes wait for 0 cycle, 2 or 4, etc.
So, you can consider that some components in a ST create some kind of
"fussyness", even if there's no real randomness in it.