From ddb29874d71a03d7a660aacf69acf85ca51277fe Mon Sep 17 00:00:00 2001
From: Natt Akuma <akumanatt925@gmail.com>
Date: Wed, 27 Nov 2024 18:37:39 +0700
Subject: [PATCH] SNES: Change base capacity to 0xf800 bytes instead of 0x10000
 This is to reflect both source address calculations in the engine code, which
 assume an echo buffer to end at 0xf800

---
 src/engine/platform/snes.cpp | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/src/engine/platform/snes.cpp b/src/engine/platform/snes.cpp
index 31f04ca26..44b3da2c6 100644
--- a/src/engine/platform/snes.cpp
+++ b/src/engine/platform/snes.cpp
@@ -841,7 +841,7 @@ void DivPlatformSNES::initEcho() {
 
   for (DivMemoryEntry& i: memCompo.entries) {
     if (i.type==DIV_MEMORY_ECHO) {
-      i.begin=(65536-echoDelay*2048);
+      i.begin=(0xf800-echoDelay*2048);
     }
   }
   memCompo.used=sampleMemLen+echoDelay*2048;
@@ -946,7 +946,7 @@ const void* DivPlatformSNES::getSampleMem(int index) {
 }
 
 size_t DivPlatformSNES::getSampleMemCapacity(int index) {
-  return index == 0 ? (65536-echoDelay*2048) : 0;
+  return index == 0 ? (0xf800-echoDelay*2048) : 0;
 }
 
 size_t DivPlatformSNES::getSampleMemUsage(int index) {
@@ -1010,7 +1010,9 @@ void DivPlatformSNES::renderSamples(int sysID) {
   }
   sampleMemLen=memPos;
 
-  memCompo.entries.push_back(DivMemoryEntry(DIV_MEMORY_ECHO,"Echo Buffer",-1,(65536-echoDelay*2048),65536));
+  // even if the delay is 0, the DSP will still operate the first buffer sample
+  // so the ARAM buffer size becomes 4 bytes when the delay is 0
+  memCompo.entries.push_back(DivMemoryEntry(DIV_MEMORY_ECHO,"Echo Buffer",-1,(0xf800-echoDelay*2048),echoDelay==0?0xf804:0xf800));
 
   memCompo.capacity=65536;
   memCompo.used=sampleMemLen+echoDelay*2048;