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Attempts to be more rigorous about clock rates.

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This commit is contained in:
Thomas Harte 2018-04-18 21:52:22 -04:00
parent 5f1c210746
commit f5ae8d0f79
1 changed files with 13 additions and 3 deletions
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16
Machines/AppleII/AppleII.cpp
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@ -72,8 +72,19 @@ class ConcreteMachine:
video_bus_handler_(ram_),
audio_toggle_(audio_queue_),
speaker_(audio_toggle_) {
set_clock_rate(1022727);
speaker_.set_input_rate(7159089.0f / 16.0f);
// The system's master clock rate.
const float master_clock = 14318180.0;
// This is where things get slightly convoluted: establish the machine as having a clock rate
// equal to the number of cycles of work the 6502 will actually achieve. Which is less than
// the master clock rate divided by 14 because every 65th cycle is extended by one seventh.
set_clock_rate((master_clock / 14.0) * 65.0 / (65.0 + 1.0 / 7.0));
// The speaker, however, should think it is clocked at half the master clock, per a general
// decision to sample it at seven times the CPU clock (plus stretches).
speaker_.set_input_rate(static_cast<float>(master_clock / (2.0 * 16.0)));
// Also, start with randomised memory contents.
Memory::Fuzz(ram_, sizeof(ram_));
}
@ -112,7 +123,6 @@ class ConcreteMachine:
*value = 0xff;
break;
case 0xc000:
// TODO: read keyboard.
*value = keyboard_input_;
break;
}