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Attempts also to implement 1Mhz access costs.

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Subject to TODO, and same observation as before: this is as to my current understanding only.
This commit is contained in:
Thomas Harte 2020-11-14 19:23:01 -05:00
parent adda3d8f42
commit f9cec9a102
1 changed files with 7 additions and 3 deletions
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10
Machines/Apple/AppleIIgs/AppleIIgs.cpp
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@ -642,8 +642,12 @@ class ConcreteMachine:
// Below is very vague on real details. Won't do.
Cycles duration;
if(is_1Mhz) {
// TODO: (i) get into phase; (ii) allow for the 1Mhz bus length being sporadically 16 rather than 14.
duration = Cycles(14);
// TODO: this is very implicitly linked to the video timing; make that overt somehow. Even if it's just with a redundant video setter at construction.
const int current_length = 14 + 2*(slow_access_phase_ / 896); // Length of cycle currently ongoing.
const int phase_adjust = (current_length - slow_access_phase_%14)%current_length; // Amount of time to expand waiting until end of cycle, if not actually at start.
const int access_phase = (slow_access_phase_ + phase_adjust)%912; // Phase at which access will begin.
const int next_length = 14 + 2*(access_phase / 896); // Length of cycle that this access will occur within.
duration = Cycles(next_length + phase_adjust);
} else {
// Clues as to 'fast' refresh timing:
//
@ -660,7 +664,7 @@ class ConcreteMachine:
duration = Cycles(5 + phase_adjust + refresh);
}
fast_access_phase_ = (fast_access_phase_ + duration.as<int>()) % 50;
slow_access_phase_ = (slow_access_phase_ + duration.as<int>()) % 14; // TODO: modulo something else, to allow for stretched cycles.
slow_access_phase_ = (slow_access_phase_ + duration.as<int>()) % 912;
// Propagate time far and wide.