From 2d766982799b03c4333b6784593c903f54d55e45 Mon Sep 17 00:00:00 2001
From: Lior Halphon <LIJI32@gmail.com>
Date: Sun, 31 Jan 2021 19:17:26 +0200
Subject: [PATCH] Emulation of NR43 bit 3 glitch on CGB-C and older

---
 Core/apu.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/Core/apu.c b/Core/apu.c
index 126dd43..c7345f0 100644
--- a/Core/apu.c
+++ b/Core/apu.c
@@ -1209,7 +1209,15 @@ void GB_apu_write(GB_gameboy_t *gb, uint8_t reg, uint8_t value)
             }
             /* Step LFSR */
             if (new_bit && (!old_bit || gb->model <= GB_MODEL_CGB_C)) {
-                step_lfsr(gb, 0);
+                if (gb->model <= GB_MODEL_CGB_C) {
+                    bool previous_narrow = gb->apu.noise_channel.narrow;
+                    gb->apu.noise_channel.narrow = true;
+                    step_lfsr(gb, 0);
+                    gb->apu.noise_channel.narrow = previous_narrow;
+                }
+                else {
+                    step_lfsr(gb, 0);
+                }
             }
             break;
         }