1 files changed, 21 insertions, 15 deletions
diff --git a/source/zx81.c b/source/zx81.c
index b8143cd..fb6f801 100644
--- a/source/zx81.c
+++ b/source/zx81.c
@@ -887,11 +887,27 @@ void ZX81Init(uint16 *text_vram, uint16* bitmap_vram, Z80 *z80)
     RAMBOT=0x4000;
     RAMTOP=RAMBOT+0x4000;
 
-    for(f=RAMBOT;f<=RAMTOP;f++)
-    	mem[f]=0;
+    for(f = RAMBOT; f <= RAMTOP; f++)
+    {
+    	mem[f] = 0;
+    }
+
+    for(f = 0; f < 8; f++)
+    {
+    	matrix[f] = 0x1f;
+    }
+
+    /* Fill the upper 32K with RET opcodes -- hopefully by simply returning
+       RET for ULA reads we save a lot of ROM patching shenanigans.
+       
+       Note that this check used to be in ZX81ReadMem, but obviously this 
+       should cut down on a *lot* of pointless expression evaluation!
+    */
+    for(f = 0x8000; f <= RAMTOP; f++)
+    {
+    	mem[f] = 0xc9;
+    }
 
-    for(f=0;f<8;f++)
-    	matrix[f]=0x1f;
 }
 
 
@@ -917,17 +933,7 @@ void ZX81HandleKey(SoftKey key, int is_pressed)
 
 Z80Byte ZX81ReadMem(Z80 *z80, Z80Word addr)
 {
-    /* Hopefully by simply returning RET for ULA reads we save a lot of
-       ROM patching shenanigans.
-    */
-    if (addr>0x7fff)
-    {
-    	return 0xc9;
-    }
-    else
-    {
-	return mem[addr];
-    }
+    return mem[addr];
 }