diff --git a/cli/emulator.c b/cli/emulator.c
index 8a0d58e..095e5e8 100644
--- a/cli/emulator.c
+++ b/cli/emulator.c
@@ -30,7 +30,8 @@ int emulator_main(int argc, char *argv[])
     // test the cpu, rom, and dmg independently and use the cpu
     // for other non-GB stuff
     dmg_new(&dmg, &cpu, &rom, &lcd);
-    cpu_bind_mem_model(&cpu, &dmg, dmg_read, dmg_write);
+    cpu.dmg = &dmg;
+    // cpu_bind_mem_model(&cpu, &dmg, dmg_read, dmg_write);
 
     cpu.pc = 0x100;
 
diff --git a/cli/imgui_example.cpp b/cli/imgui_example.cpp
index 64a5e77..55d6fe4 100644
--- a/cli/imgui_example.cpp
+++ b/cli/imgui_example.cpp
@@ -156,7 +156,8 @@ int main(int argc, char *argv[])
     // test the cpu, rom, and dmg independently and use the cpu
     // for other non-GB stuff
     dmg_new(&dmg, &cpu, &rom, &lcd);
-    cpu_bind_mem_model(&cpu, &dmg, dmg_read, dmg_write);
+    cpu.dmg = &dmg;
+    // cpu_bind_mem_model(&cpu, &dmg, dmg_read, dmg_write);
 
     cpu.pc = 0x100;
 
diff --git a/src/cpu.c b/src/cpu.c
index 4e07831..d8b912d 100644
--- a/src/cpu.c
+++ b/src/cpu.c
@@ -2,20 +2,10 @@
 #include <stdlib.h>
 
 #include "cpu.h"
+#include "dmg.h"
 #include "types.h"
 #include "instructions.h"
 
-void cpu_bind_mem_model(
-    struct cpu *cpu,
-    void *mem_model,
-    u8 (*mem_read)(void *, u16),
-    void (*mem_write)(void *, u16, u8)
-) {
-    cpu->mem_model = mem_model;
-    cpu->mem_read = mem_read;
-    cpu->mem_write = mem_write;
-}
-
 int flag_isset(struct cpu *cpu, int flag)
 {
     return (cpu->f & flag) != 0;
@@ -66,7 +56,7 @@ void cpu_panic(struct cpu *cpu)
 
 static inline u8 read8(struct cpu *cpu, u16 address)
 {
-    return cpu->mem_read(cpu->mem_model, address);
+    return dmg_read(cpu->dmg, address);
 }
 
 static inline u16 read16(struct cpu *cpu, u16 address)
@@ -78,12 +68,12 @@ static inline u16 read16(struct cpu *cpu, u16 address)
 
 static inline void write8(struct cpu *cpu, u16 address, u8 data)
 {
-    cpu->mem_write(cpu->mem_model, address, data);
+    dmg_write(cpu->dmg, address, data);
 }
 
 static inline void write16(struct cpu *cpu, u16 address, u16 data)
 {
-    cpu->mem_write(cpu->mem_model, address, data);
+    dmg_write(cpu->dmg, address, data);
 }
 
 static void inc_with_carry(struct cpu *regs, u8 *reg)
@@ -493,15 +483,15 @@ static u16 check_interrupts(struct cpu *cpu)
         return 0;
     }
 
-    u16 enabled = cpu->mem_read(cpu->mem_model, 0xffff);
-    u16 requested = cpu->mem_read(cpu->mem_model, 0xff0f);
+    u16 enabled = dmg_read(cpu->dmg, 0xffff);
+    u16 requested = dmg_read(cpu->dmg, 0xff0f);
 
     for (k = 0; k < NUM_INTERRUPTS; k++) {
         int check = 1 << k;
         if ((enabled & check) && (requested & check)) {
             // clear request flag for this interrupt and disable all further
             // interrupts until service routine executes EI or RETI
-            cpu->mem_write(cpu->mem_model, 0xff0f, requested & ~check);
+            dmg_write(cpu->dmg, 0xff0f, requested & ~check);
             cpu->interrupt_enable = 0;
             return handlers[k];
         }
@@ -522,7 +512,7 @@ void cpu_step(struct cpu *cpu)
         return;
     }
 
-    u8 opc = cpu->mem_read(cpu->mem_model, cpu->pc);
+    u8 opc = dmg_read(cpu->dmg, cpu->pc);
 #ifdef GB6_DEBUG
     printf("0x%04x %s\n", cpu->pc, instructions[opc].format);
 #endif
diff --git a/src/cpu.h b/src/cpu.h
index 9f0b659..466e99f 100644
--- a/src/cpu.h
+++ b/src/cpu.h
@@ -3,6 +3,8 @@
 
 #include "types.h"
 
+struct dmg;
+
 struct cpu
 {
     u8 a;
@@ -18,17 +20,18 @@ struct cpu
     u32 cycle_count;
     u8 interrupt_enable;
 
-    u8 (*mem_read)(void *, u16);
-    void (*mem_write)(void *, u16, u8);
-    void *mem_model;
+    struct dmg *dmg;
+    // u8 (*mem_read)(void *, u16);
+    // void (*mem_write)(void *, u16, u8);
+    // void *mem_model;
 };
 
-void cpu_bind_mem_model(
-    struct cpu *cpu,
-    void *mem_model,
-    u8 (*mem_read)(void *, u16),
-    void (*mem_write)(void *, u16, u8)
-);
+// void cpu_bind_mem_model(
+//     struct cpu *cpu,
+//     void *mem_model,
+//     u8 (*mem_read)(void *, u16),
+//     void (*mem_write)(void *, u16, u8)
+// );
 
 void cpu_step(struct cpu *cpu);
 int flag_isset(struct cpu *cpu, int flag);
diff --git a/src/dmg.c b/src/dmg.c
index 833d6cf..8dfffe0 100644
--- a/src/dmg.c
+++ b/src/dmg.c
@@ -262,22 +262,22 @@ void dmg_step(void *_dmg)
                 dmg_request_interrupt(dmg, INT_LCDSTAT);
             }
 
-            int lcdc = lcd_read(dmg->lcd, REG_LCDC);
-            if (lcdc & LCDC_ENABLE_BG) {
-                render_background(dmg, lcdc);
-            }
+            // int lcdc = lcd_read(dmg->lcd, REG_LCDC);
+            // if (lcdc & LCDC_ENABLE_BG) {
+            //     render_background(dmg, lcdc);
+            // }
 
-            if (lcdc & LCDC_ENABLE_WINDOW) {
-                // printf("window\n");
-            }
+            // if (lcdc & LCDC_ENABLE_WINDOW) {
+            //     // printf("window\n");
+            // }
 
-            lcd_apply_scroll(dmg->lcd);
+            // lcd_apply_scroll(dmg->lcd);
 
-            if (lcdc & LCDC_ENABLE_OBJ) {
-                render_objs(dmg);
-            }
+            // if (lcdc & LCDC_ENABLE_OBJ) {
+            //     render_objs(dmg);
+            // }
 
-            lcd_draw(dmg->lcd);
+            // lcd_draw(dmg->lcd);
         }
     } else {
         int scan = lcd_read(dmg->lcd, REG_LY);
diff --git a/src/mbc.c b/src/mbc.c
index f556152..33f434b 100644
--- a/src/mbc.c
+++ b/src/mbc.c
@@ -6,16 +6,6 @@
 #include "dmg.h"
 #include "rom.h"
 
-static int mbc_noop_read(struct mbc *mbc, struct dmg *dmg, u16 addr, u8 *out_data)
-{
-  return 0;
-}
-
-static int mbc_noop_write(struct mbc *mbc, struct dmg *dmg, u16 addr, u8 data)
-{
-  return 0;
-}
-
 static int mbc1_read(struct mbc *mbc, struct dmg *dmg, u16 addr, u8 *out_data)
 {
   if (addr >= 0x4000 && addr <= 0x7fff) {
@@ -60,35 +50,29 @@ static int mbc1_write(struct mbc *mbc, struct dmg *dmg, u16 addr, u8 data)
   return 0;
 }
 
-struct mbc mbc_noop = {
-  mbc_noop_read,
-  mbc_noop_write,
-};
-
-struct mbc mbc1 = {
-  mbc1_read,
-  mbc1_write,
-};
-
 struct mbc *mbc_new(int type)
 {
-  switch (type) {
-    case 0:
-      return &mbc_noop;
-    case 1:
-    case 2:
-    case 3:
-      return &mbc1;
+  static struct mbc mbc;
+  if (type > 3) {
+    return NULL;
   }
-  return NULL;
+  mbc.type = type;
+
+  return &mbc;
 }
 
 int mbc_read(struct mbc *mbc, struct dmg *dmg, u16 addr, u8 *out_data)
 {
-  return mbc->read_fn(mbc, dmg, addr, out_data);
+  if (mbc->type == 0) {
+    return 0;
+  }
+  return mbc1_read(mbc, dmg, addr, out_data);
 }
 
 int mbc_write(struct mbc *mbc, struct dmg *dmg, u16 addr, u8 data)
 {
-  return mbc->write_fn(mbc, dmg, addr, data);
+  if (mbc->type == 0) {
+    return 0;
+  }
+  return mbc1_write(mbc, dmg, addr, data);
 }
diff --git a/src/mbc.h b/src/mbc.h
index d1d429b..fb9c62a 100644
--- a/src/mbc.h
+++ b/src/mbc.h
@@ -6,8 +6,6 @@
 struct dmg;
 
 struct mbc {
-  int (*read_fn)(struct mbc *, struct dmg *, u16, u8 *);
-  int (*write_fn)(struct mbc *, struct dmg *, u16, u8);
   int type;
   int rom_bank;
   int ram_bank;
@@ -16,7 +14,10 @@ struct mbc {
 };
 
 struct mbc *mbc_new(int type);
+
+// set *out_data and return 1 if handled, return 0 for base dmg behavior
 int mbc_read(struct mbc *mbc, struct dmg *dmg, u16 addr, u8 *out_data);
+// return 1 if handled, return 0 for base dmg behavior
 int mbc_write(struct mbc *mbc, struct dmg *dmg, u16 addr, u8 data);
 
 #endif
\ No newline at end of file
diff --git a/system6/emulator.c b/system6/emulator.c
index b2bea9a..3bd404f 100644
--- a/system6/emulator.c
+++ b/system6/emulator.c
@@ -59,18 +59,18 @@ Rect offscreenRect = { 0, 0, 144, 160 };
 
 BitMap offscreenBmp;
 
-int lastTicks;
+int execTime;
 
 void Render(void)
 {
-  long k = 0, dst, bit;
-  for (dst = 0; dst < 20 * 144; dst++) {
-    for (bit = 7; bit >= 0; bit--) {
-      offscreen[dst] |= lcd.pixels[k++];
-      offscreen[dst] <<= 1;
-    }
-    dst++;
-  }
+  // long k = 0, dst, bit;
+  // for (dst = 0; dst < 20 * 144; dst++) {
+  //   for (bit = 7; bit >= 0; bit--) {
+  //     offscreen[dst] |= lcd.pixels[k++];
+  //     offscreen[dst] <<= 1;
+  //   }
+  //   dst++;
+  // }
 
   /*
     offscreen[dst] = lcd.pixels[k++] << 7;
@@ -83,16 +83,25 @@ void Render(void)
     offscreen[dst] |= lcd.pixels[k++];
   */
   SetPort(g_wp);
-  CopyBits(&offscreenBmp, &g_wp->portBits, &offscreenRect, &offscreenRect, srcCopy, NULL);
+  // CopyBits(&offscreenBmp, &g_wp->portBits, &offscreenRect, &offscreenRect, srcCopy, NULL);
 
-  //EraseRect(&g_wp->portRect);
-  // MoveTo(10, 160);
-  // char debug[128];
-  // sprintf(debug, "PC: %04x", cpu.pc);
-  // C2PStr(debug);
-  // DrawString(debug);
+  EraseRect(&g_wp->portRect);
+  MoveTo(10, 180);
+  char debug[128];
+  double ms = execTime / 600.0;
+  sprintf(debug, "10000 insn %d ticks, %f ms per instruction", execTime, ms);
+  C2PStr(debug);
+  DrawString(debug);
 }
 
+// 417 ticks
+// 10000 instructions
+
+// 0.0417 tick per instruction
+// 1/60 second per tick
+// 0.000695 second per instruction
+// 0.695 ms per instruction
+
 void StartEmulation(void)
 {
   g_wp = NewWindow(0, &windowBounds, WINDOW_TITLE, true, 
@@ -188,7 +197,7 @@ void ShowAboutBox(void)
   // DrawDialog(dp);
   // while(!GetNextEvent(mDownMask, &e));
   // while(WaitMouseUp());
-  
+
   DisposeDialog(dp);
 }
 
@@ -264,25 +273,26 @@ int main(int argc, char *argv[])
   int executed;
   int paused = 0;
   int pause_next = 0;
-  
+
   InitEverything();
 
   lcd_new(&lcd);
   dmg_new(&dmg, &cpu, &rom, &lcd);
-  cpu_bind_mem_model(&cpu, &dmg, dmg_read, dmg_write);
+  cpu.dmg = &dmg;
+  // cpu_bind_mem_model(&cpu, &dmg, dmg_read, dmg_write);
 
   cpu.pc = 0x100;
-  
-  int start = TickCount();
+
   while(g_running) {
     if (emulationOn) {
+      int k;
+      int start = TickCount();
+      for (k = 0; k < 10000; k++) {
         dmg_step(&dmg);
-        int now = TickCount();
-        if (now > lastTicks + 100) {
-          lastTicks = now;
-          Render();
-        }
-      if (Button()) g_running = false;
+      }
+      execTime = TickCount() - start;
+      emulationOn = false;
+      Render();
     } else {
       if(WaitNextEvent(everyEvent, &evt, 0, 0) != nullEvent) {
         if (IsDialogEvent(&evt)) {