From cdecb9165e66fa5ffa83a9f06daf64a2932c4925 Mon Sep 17 00:00:00 2001
From: Thomas Jentzsch <tjentzsch@yahoo.de>
Date: Mon, 11 Apr 2022 09:14:01 +0200
Subject: [PATCH] improved bank origin detection (fixes #428)

---
 src/debugger/CartDebug.cxx | 2 +-
 src/emucore/Cart.cxx       | 8 +++++---
 src/emucore/Cart.hxx       | 3 ++-
 3 files changed, 8 insertions(+), 5 deletions(-)

diff --git a/src/debugger/CartDebug.cxx b/src/debugger/CartDebug.cxx
index 0db637fba..fa04d14ea 100644
--- a/src/debugger/CartDebug.cxx
+++ b/src/debugger/CartDebug.cxx
@@ -290,7 +290,7 @@ bool CartDebug::disassemble(int bank, uInt16 PC, bool force)
     // If the offset has changed, all old addresses must be 'converted'
     // For example, if the list contains any $fxxx and the address space is now
     // $bxxx, it must be changed
-    uInt16 offset = (PC - (PC % 0x1000));
+    uInt16 offset = myConsole.cartridge().bankOrigin(bank, PC);
     AddressList& addresses = info.addressList;
     for(auto& i: addresses)
       i = (i & 0xFFF) + offset;
diff --git a/src/emucore/Cart.cxx b/src/emucore/Cart.cxx
index 8f6362753..ed57ff42e 100644
--- a/src/emucore/Cart.cxx
+++ b/src/emucore/Cart.cxx
@@ -180,10 +180,10 @@ string Cartridge::getAccessCounters() const
 }
 
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
-uInt16 Cartridge::bankOrigin(uInt16 bank) const
+uInt16 Cartridge::bankOrigin(uInt16 bank, uInt16 PC) const
 {
-  // isolate the high 3 address bits, count them and
-  // select the most frequent to define the bank origin
+  // Isolate the high 3 address bits, count them, include the PC if provided
+  // and select the most frequent to define the bank origin
   // TODO: origin for banks smaller than 4K
   constexpr int intervals = 0x8000 / 0x100;
   const uInt32 offset = bank * bankSize();
@@ -196,6 +196,8 @@ uInt16 Cartridge::bankOrigin(uInt16 bank) const
   //addrMask;
 
   count.fill(0);
+  if(PC)
+    count[PC >> 13]++;
   for(uInt16 addr = 0x0000; addr < bankSize(bank); ++addr)
   {
     const Device::AccessFlags flags = myRomAccessBase[offset + addr];
diff --git a/src/emucore/Cart.hxx b/src/emucore/Cart.hxx
index a5171e6f1..67e66e039 100644
--- a/src/emucore/Cart.hxx
+++ b/src/emucore/Cart.hxx
@@ -189,9 +189,10 @@ class Cartridge : public Device
       Determine the bank's origin
 
       @param bank  The bank to query
+      @param PC    The current PC
       @return  The origin of the bank
     */
-    uInt16 bankOrigin(uInt16 bank) const;
+    uInt16 bankOrigin(uInt16 bank, uInt16 PC = 0) const;
   #endif
 
   public: