From 7dfb015dd550cc93f6951d815122b0134d650ced Mon Sep 17 00:00:00 2001
From: Matt Nadareski <mnadareski@outlook.com>
Date: Fri, 6 Mar 2026 13:23:17 -0500
Subject: [PATCH] Fix reading PRG and CHR

---
 SabreTools.Serialization/Readers/NESCart.cs | 20 ++++++++++++++------
 1 file changed, 14 insertions(+), 6 deletions(-)

diff --git a/SabreTools.Serialization/Readers/NESCart.cs b/SabreTools.Serialization/Readers/NESCart.cs
index abd57f35..ccfcb2df 100644
--- a/SabreTools.Serialization/Readers/NESCart.cs
+++ b/SabreTools.Serialization/Readers/NESCart.cs
@@ -42,16 +42,24 @@ namespace SabreTools.Serialization.Readers
 #endif
                     cart.Trainer = data.ReadBytes(512);
 
-                // Read the PRG-ROM data
+                // Derive the PRG-ROM and CHR-ROM data sizes
                 // TODO: Make model for PRG-ROM data blocks
-                // TODO: Use combined size from 2.0
                 int prgRomSize = cart.Header.PRGROMSize * 16384;
+                int chrRomSize = cart.Header.CHRROMSize * 8192;
+                if (cart.Header is Header2 header2)
+                {
+                    byte msb = (byte)(header2.PRGCHRMSB & 0x0F);
+                    ushort extendedSize = (ushort)((msb << 8) | header.PRGROMSize);
+                    prgRomSize = extendedSize * 16384;
+
+                    msb = (byte)(header2.PRGCHRMSB >> 4);
+                    extendedSize = (ushort)((msb << 8) | header.CHRROMSize);
+                    chrRomSize = extendedSize * 8192;
+                }
+
+                // Read the PRG-ROM and CHR-ROM data
                 if (prgRomSize > 0)
                     cart.PRGROMData = data.ReadBytes(prgRomSize);
-
-                // Read the CHR-ROM data, if necessary
-                // TODO: Use combined size from 2.0
-                int chrRomSize = cart.Header.CHRROMSize * 8192;
                 if (chrRomSize > 0)
                     cart.CHRROMData = data.ReadBytes(chrRomSize);