--- a/z80_util.c	Fri Feb 08 23:09:58 2019 -0800
+++ b/z80_util.c	Sat Feb 09 11:34:31 2019 -0800
@@ -3,13 +3,23 @@
 void z80_read_8(z80_context *context)
 {
 	context->cycles += 3 * context->opts->gen.clock_divider;
-	context->scratch1 = read_byte(context->scratch1, NULL, &context->opts->gen, context);
+	uint8_t *fast = context->fastmem[context->scratch1 >> 10];
+	if (fast) {
+		context->scratch1 = fast[context->scratch1 & 0x3FF];
+	} else {
+		context->scratch1 = read_byte(context->scratch1, NULL, &context->opts->gen, context);
+	}
 }
 
 void z80_write_8(z80_context *context)
 {
 	context->cycles += 3 * context->opts->gen.clock_divider;
-	write_byte(context->scratch2, context->scratch1, NULL, &context->opts->gen, context);
+	uint8_t *fast = context->fastmem[context->scratch2 >> 10];
+	if (fast) {
+		fast[context->scratch2 & 0x3FF] = context->scratch1;
+	} else {
+		write_byte(context->scratch2, context->scratch1, NULL, &context->opts->gen, context);
+	}
 }
 
 void z80_io_read8(z80_context *context)
@@ -69,6 +79,16 @@
 	context->io_map = (memmap_chunk *)tmp_io_chunks;
 	context->io_chunks = tmp_num_io_chunks;
 	context->io_mask = tmp_io_mask;
+	for(uint32_t address = 0; address < 0x10000; address+=1024)
+	{
+		uint8_t *start = get_native_pointer(address, NULL, &options->gen);
+		if (start) {
+			uint8_t *end = get_native_pointer(address + 1023, NULL, &options->gen);
+			if (end && end - start == 1023) {
+				context->fastmem[address >> 10] = start;
+			}
+		}
+	}
 	return context;
 }