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author arekkusu42 <arekkusu42@users.noreply.github.com>2025-09-15 12:27:37 -0700
committer GitHub <noreply@github.com>2025-09-15 15:27:37 -0400
commit2db560e9bf52321470de464f0adc29146ecaf97a (patch)
treec4204e96294c30a953d53556aa7e12257d1dfb2d
parent588abdae8f7823e84e317e3c0f9b3b6d9480ea65 (diff)
apple2gs: Fix $C019 VBL (#14177)
$C019 is inverted compared to the //e. This fixes tearing/flickering/missing graphics in various demos (by ACS, FTA, Brutal Deluxe, etc.)
-rw-r--r--src/mame/apple/apple2gs.cpp4
1 files changed, 2 insertions, 2 deletions
diff --git a/src/mame/apple/apple2gs.cpp b/src/mame/apple/apple2gs.cpp
index b743dbfc329..0de449a30fe 100644
--- a/src/mame/apple/apple2gs.cpp
+++ b/src/mame/apple/apple2gs.cpp
@@ -1559,8 +1559,8 @@ u8 apple2gs_state::c000_r(offs_t offset)
case 0x18: // read 80STORE
return (uKeyboardC010 & 0x7f) | (m_video->get_80store() ? 0x80 : 0x00);
- case 0x19: // read VBLBAR
- return (uKeyboardC010 & 0x7f) | (m_screen->vblank() ? 0x00 : 0x80);
+ case 0x19: // read VBL (not VBLBAR, see Apple IIGS Technical Note #40)
+ return (uKeyboardC010 & 0x7f) | (m_screen->vblank() ? 0x80 : 0x00);
case 0x1a: // read TEXT
return (uKeyboardC010 & 0x7f) | (m_video->get_graphics() ? 0x00 : 0x80);