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Adjust CGA clocking down by 1/7th.

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This commit is contained in:
Thomas Harte 2023-12-07 12:05:15 -05:00
parent d94791a82d
commit 8608f0f89d
1 changed files with 6 additions and 5 deletions
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11
Machines/PCCompatible/CGA.hpp
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@ -30,11 +30,12 @@ class CGA {
void run_for(Cycles cycles) { void run_for(Cycles cycles) {
// Input rate is the PIT rate of 1,193,182 Hz. // Input rate is the PIT rate of 1,193,182 Hz.
// CGA is clocked at the real oscillator rate of 14 times that. // CGA is clocked at the real oscillator rate of 12 times that.
// But there's also an internal divide by 8 to align to the fetch clock. // But there's also an internal divide by 8 to align to the 80-cfetch clock.
full_clock_ += 7 * cycles.as<int>(); // ... and 12/8 = 3/2.
full_clock_ += 3 * cycles.as<int>();
const int modulo = 4 * outputter_.clock_divider; const int modulo = 2 * outputter_.clock_divider;
crtc_.run_for(Cycles(full_clock_ / modulo)); crtc_.run_for(Cycles(full_clock_ / modulo));
full_clock_ %= modulo; full_clock_ %= modulo;
} }
@ -90,7 +91,7 @@ class CGA {
} }
Outputs::Display::ScanStatus get_scaled_scan_status() const { Outputs::Display::ScanStatus get_scaled_scan_status() const {
return outputter_.crt.get_scaled_scan_status() * 4.0f / (7.0f * 8.0f); return outputter_.crt.get_scaled_scan_status() * float(outputter_.clock_divider) / (3.0f * 4.0f);
} }
private: private: