From 53a0ae7d11b82ab13564f2c82f43407337343d67 Mon Sep 17 00:00:00 2001 From: arbee Date: Tue, 12 Apr 2022 21:25:03 -0400 Subject: apple2gs: fix slow cycles to a more correct value. (MT#08240) [R. Belmont] --- src/mame/drivers/apple2gs.cpp | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/src/mame/drivers/apple2gs.cpp b/src/mame/drivers/apple2gs.cpp index 2907177cc8c..1fd17fd29b8 100644 --- a/src/mame/drivers/apple2gs.cpp +++ b/src/mame/drivers/apple2gs.cpp @@ -620,11 +620,13 @@ private: // FF6ACF is speed test routine in ROM 3 +// slow_cycle() - take a 1 MHz cycle. Theory: a 2.8 MHz cycle is 14M / 5. +// 1 MHz is 14M / 14. 14/5 = 2.8 * 65536 (16.16 fixed point) = 0x2cccd. #define slow_cycle() \ { \ if (!machine().side_effects_disabled() && m_last_speed) \ {\ - m_slow_counter += 0x0001999a; \ + m_slow_counter += 0x0002cccd; \ int cycles = (m_slow_counter >> 16) & 0xffff; \ m_slow_counter &= 0xffff; \ m_maincpu->adjust_icount(-cycles); \ -- cgit v1.2.3