--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/multi_game.c	Sat Jun 24 13:55:54 2017 -0700
@@ -0,0 +1,26 @@
+#include "genesis.h"
+
+void *write_multi_game_b(uint32_t address, void *vcontext, uint8_t value)
+{
+	m68k_context *context = vcontext;
+	genesis_context *gen = context->system;
+	uint32_t base = (address & 0x3F) << 16, start = 0, end = 0x400000;
+	//find the memmap chunk, so we can properly mask the base value
+	for (int i = 0; i < context->options->gen.memmap_chunks; i++)
+	{
+		if (context->options->gen.memmap[i].flags & MMAP_PTR_IDX) {
+			base &= context->options->gen.memmap[i].mask;
+			start = context->options->gen.memmap[i].start;
+			end = context->options->gen.memmap[i].end;
+			break;
+		}
+	}
+	context->mem_pointers[gen->mapper_start_index] = gen->cart + base/2;
+	m68k_invalidate_code_range(context, start, end);
+	return vcontext;
+}
+
+void *write_multi_game_w(uint32_t address, void *context, uint16_t value)
+{
+	return write_multi_game_b(address, context, value);
+}