From dd53b01f761a6801e7922c993e81048f2c6d7c0a Mon Sep 17 00:00:00 2001
From: RSDuck <RSDuck@users.noreply.github.com>
Date: Sun, 27 Jun 2021 00:45:12 +0200
Subject: [PATCH] only recalculate GBA slot timing if necessary

---
 src/NDS.cpp | 22 +++++++++++++++-------
 1 file changed, 15 insertions(+), 7 deletions(-)

diff --git a/src/NDS.cpp b/src/NDS.cpp
index 53f57ca2..16547efb 100644
--- a/src/NDS.cpp
+++ b/src/NDS.cpp
@@ -3329,10 +3329,14 @@ void ARM9IOWrite16(u32 addr, u16 val)
     case 0x040001BA: ROMSeed1[4] = val & 0x7F; return;
 
     case 0x04000204:
-        ExMemCnt[0] = val;
-        ExMemCnt[1] = (ExMemCnt[1] & 0x007F) | (val & 0xFF80);
-        SetGBASlotTimings();
-        return;
+        {
+            u16 oldVal = ExMemCnt[0];
+            ExMemCnt[0] = val;
+            ExMemCnt[1] = (ExMemCnt[1] & 0x007F) | (val & 0xFF80);
+            if ((oldVal ^ ExMemCnt[0]) & 0xFF)
+                SetGBASlotTimings();
+            return;
+        }
 
     case 0x04000208: IME[0] = val & 0x1; UpdateIRQ(0); return;
     case 0x04000210: IE[0] = (IE[0] & 0xFFFF0000) | val; UpdateIRQ(0); return;
@@ -4038,9 +4042,13 @@ void ARM7IOWrite16(u32 addr, u16 val)
         return;
 
     case 0x04000204:
-        ExMemCnt[1] = (ExMemCnt[1] & 0xFF80) | (val & 0x007F);
-        SetGBASlotTimings();
-        return;
+        {
+            u16 oldVal = ExMemCnt[1];
+            ExMemCnt[1] = (ExMemCnt[1] & 0xFF80) | (val & 0x007F);
+            if ((ExMemCnt[1] ^ oldVal) & 0xFF)
+                SetGBASlotTimings();
+            return;
+        }
     case 0x04000206:
         SetWifiWaitCnt(val);
         return;