[hatari-devel] Old vs New CPU

[Miro Kropáček]

Addendum: really, don't take it that serious with the cycle counting.
Yesterday, just before I fell asleep I went thru the 68030 UM. First of all,
the heads/tails apply only for cache-case, i.e. for no-cache-cases those
numbers do not apply. Therefore I'm more confident you can just add the
number of tail/head cycles to the overall sum of the falcon cycle count.

Second, and it's emphasized on many places in the book, those numbers are
only for the general idea how fast / slow is an instruction flow in
comparison to another one. For example, instruction prefetch times are
_average_ of best and worst cases, i.e. in many cases the overall cycle
count varies even by a few cycles => some head/tail stuff really doesn't
matter, you can never get 100% accurate emulation.

IMO, the most important thing which needs to be done is the number of bus
cycles taken for each instruction, i.e. when you do:

.loop: move.w (a1),(a0)+
dbra d7,.loop

you give the DSP a time for let's say 5 instructions without any further
synchronization on the CPU side.

-- 
MiKRO / Mystic Bytes
http://mikro.atari.org
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