chore: resolve incorrect memory mirror in VRAM

+ stub GPIO registers on ROM Write

src/bus/GamePak.zig

@@ -113,20 +113,31 @@ pub fn write(self: *Self, comptime T: type, word_count: u16, address: u32, value
         }
     }
 
-    log.err("Wrote {} {X:} to 0x{X:0>8}", .{ T, value, address });
+    switch (T) {
+        u32 => switch (address) {
+            0x0800_00C4 => log.err("Wrote {} 0x{X:} to I/O Port Data and Direction", .{ T, value }),
+            0x0800_00C6 => log.err("Wrote {} 0x{X:} to I/O Port Direction and Control", .{ T, value }),
+            else => {},
+        },
+        u16 => switch (address) {
+            0x0800_00C4 => log.err("Wrote {} 0x{X:} to I/O Port Data", .{ T, value }),
+            0x0800_00C6 => log.err("Wrote {} 0x{X:} to I/O Port Direction", .{ T, value }),
+            0x0800_00C8 => log.err("Wrote {} 0x{X:} to I/O Port Control", .{ T, value }),
+            else => {},
+        },
+        u8 => log.warn("Wrote {} 0x{X:} to 0x{X:0>8}, Ignored.", .{ T, value, address }),
+        else => @compileError("GamePak: Unsupported write width"),
+    }
 }
 
 fn get(self: *const Self, i: u32) u8 {
     @setRuntimeSafety(false);
+    if (i < self.buf.len) return self.buf[i];
 
-    if (i >= self.buf.len) {
     const lhs = i >> 1 & 0xFFFF;
     return @truncate(u8, lhs >> 8 * @truncate(u5, i & 1));
 }
 
-    return self.buf[i];
-}
-
 test "OOB Access" {
     const title = .{ 'H', 'E', 'L', 'L', 'O', ' ', 'W', 'O', 'R', 'L', 'D', '!' };
     const alloc = std.testing.allocator;

src/ppu.zig

@@ -600,8 +600,12 @@ const Vram = struct {
     }
 
     fn mirror(address: usize) usize {
-        const addr = address & 0x1FFFF; // repeated in steps of 128KiB
-        return if (addr >= 0x18000) addr & 0x7FFF else addr; // 64K + 32K + 32K (abcc)
+        // Mirrored in steps of 128K (64K + 32K + 32K) (abcc)
+        const addr = address & 0x1FFFF;
+
+        // If the address is within 96K we don't do anything,
+        // otherwise we want to mirror the last 32K (addresses between 64K and 96K)
+        return if (addr < vram_size) addr else 0x10000 + (addr & 0x7FFF);
     }
 };