diff --git a/gameboy/Makefile b/gameboy/Makefile
index d368bc29..ecb87ae3 100755
--- a/gameboy/Makefile
+++ b/gameboy/Makefile
@@ -1,10 +1,13 @@
 gameboy_objects := libco
-gameboy_objects += gameboy-system gameboy-cartridge gameboy-memory gameboy-cpu
+gameboy_objects += gameboy-system gameboy-scheduler
+gameboy_objects += gameboy-cartridge gameboy-memory
+gameboy_objects += gameboy-cpu
 objects += $(gameboy_objects)
 
 obj/libco.o: libco/libco.c libco/*
 
 obj/gameboy-system.o: $(gameboy)/system/system.cpp $(call rwildcard,$(gameboy)/system/)
+obj/gameboy-scheduler.o: $(gameboy)/scheduler/scheduler.cpp $(call rwildcard,$(gameboy)/scheduler/)
 obj/gameboy-cartridge.o: $(gameboy)/cartridge/cartridge.cpp $(call rwildcard,$(gameboy)/cartridge/)
 obj/gameboy-memory.o: $(gameboy)/memory/memory.cpp $(call rwildcard,$(gameboy)/memory/)
 obj/gameboy-cpu.o: $(gameboy)/cpu/cpu.cpp $(call rwildcard,$(gameboy)/cpu/)
diff --git a/gameboy/cartridge/cartridge.cpp b/gameboy/cartridge/cartridge.cpp
index 4b7bbfdf..b900cbbc 100755
--- a/gameboy/cartridge/cartridge.cpp
+++ b/gameboy/cartridge/cartridge.cpp
@@ -41,7 +41,6 @@ void Cartridge::load(uint8_t *data, unsigned size) {
   }
 
   loaded = true;
-  system.interface->message({ "Loaded:\n", info.name });
 }
 
 void Cartridge::unload() {
diff --git a/gameboy/cpu/core/core.cpp b/gameboy/cpu/core/core.cpp
new file mode 100755
index 00000000..d81d9f71
--- /dev/null
+++ b/gameboy/cpu/core/core.cpp
@@ -0,0 +1,91 @@
+#ifdef CPU_CPP
+
+#include "disassembler.cpp"
+
+unsigned opcode_counter = 0;
+
+void CPU::op_unknown() {
+  uint8 opcode = bus.read(--r[PC]);
+  print(
+    "CPU: unknown opcode [", hex<2>(opcode), "]\n",
+    "af:", hex<4>(r[AF]), " bc:", hex<4>(r[BC]), " de:", hex<4>(r[DE]), " hl:", hex<4>(r[HL]), " ",
+    "sp:", hex<4>(r[SP]), " pc:", hex<4>(r[PC]), "\n",
+    "ly:", decimal<3, ' '>(status.lycounter), " exec:", opcode_counter, "\n"
+  );
+  while(true) scheduler.exit();
+}
+
+//8-bit load commands
+
+template<unsigned x> void CPU::op_ld_r_n() {
+  r[x] = op_read(r[PC]++);
+}
+
+void CPU::op_ldd_hl_a() {
+  op_write(r[HL], r[A]);
+  r[HL]--;
+}
+
+//16-bit load commands
+
+template<unsigned x, unsigned y> void CPU::op_ld_rr_nn() {
+  r[y] = op_read(r[PC]++);
+  r[x] = op_read(r[PC]++);
+}
+
+//8-bit arithmetic commands
+
+template<unsigned x> void CPU::op_xor_r() {
+  r[A] ^= r[x];
+  r.f.z = r[A] == 0;
+  r.f.n = 0;
+  r.f.h = 0;
+  r.f.c = 0;
+}
+
+template<unsigned x> void CPU::op_dec_r() {
+  r[x]--;
+  r.f.z = r[x] == 0;
+  r.f.n = 0;  //???
+  r.f.h = 0;  //???
+}
+
+//control commands
+
+void CPU::op_nop() {
+}
+
+//jump commands
+
+void CPU::op_jp_nn() {
+  uint8 lo = op_read(r[PC]++);
+  uint8 hi = op_read(r[PC]++);
+  r[PC] = (hi << 8) | (lo << 0);
+  op_io();
+}
+
+template<unsigned x, bool y> void CPU::op_jr_f_n() {
+  int8 n = op_read(r[PC]++);
+  if(r.f[x] == y) {
+    r[PC] += n;
+    op_io();
+  }
+}
+
+void CPU::initialize_opcode_table() {
+  for(unsigned n = 0; n < 256; n++) opcode_table[n] = &CPU::op_unknown;
+
+  opcode_table[0x00] = &CPU::op_nop;
+  opcode_table[0x05] = &CPU::op_dec_r<B>;
+  opcode_table[0x06] = &CPU::op_ld_r_n<B>;
+  opcode_table[0x0d] = &CPU::op_dec_r<C>;
+  opcode_table[0x0e] = &CPU::op_ld_r_n<C>;
+  opcode_table[0x20] = &CPU::op_jr_f_n<ZF, 0>;
+  opcode_table[0x21] = &CPU::op_ld_rr_nn<H, L>;
+  opcode_table[0x32] = &CPU::op_ldd_hl_a;
+  opcode_table[0x3e] = &CPU::op_ld_r_n<A>;
+  opcode_table[0xaf] = &CPU::op_xor_r<A>;
+  opcode_table[0xc3] = &CPU::op_jp_nn;
+}
+
+#endif
diff --git a/gameboy/cpu/core/core.hpp b/gameboy/cpu/core/core.hpp
new file mode 100755
index 00000000..86c9ee04
--- /dev/null
+++ b/gameboy/cpu/core/core.hpp
@@ -0,0 +1,27 @@
+#include "registers.hpp"
+void (CPU::*opcode_table[256])();
+void initialize_opcode_table();
+
+void op_unknown();
+
+//8-bit load commands
+template<unsigned x> void op_ld_r_n();
+void op_ldd_hl_a();
+
+//16-bit load commands
+template<unsigned x, unsigned y> void op_ld_rr_nn();
+
+//8-bit arithmetic commands
+template<unsigned x> void op_xor_r();
+template<unsigned x> void op_dec_r();
+
+//control commands
+void op_nop();
+
+//jump commands
+void op_jp_nn();
+template<unsigned x, bool y> void op_jr_f_n();
+
+//disassembler.cpp
+string disassemble(uint16 pc);
+string disassemble_opcode(uint16 pc);
diff --git a/gameboy/cpu/core/disassembler.cpp b/gameboy/cpu/core/disassembler.cpp
new file mode 100755
index 00000000..85e8e551
--- /dev/null
+++ b/gameboy/cpu/core/disassembler.cpp
@@ -0,0 +1,30 @@
+#ifdef CPU_CPP
+
+string CPU::disassemble(uint16 pc) {
+  return { hex<4>(pc), "  ", disassemble_opcode(pc) };
+}
+
+string CPU::disassemble_opcode(uint16 pc) {
+  uint8 opcode = bus.read(pc);
+  uint8 p0 = bus.read(pc + 1);
+  uint8 p1 = bus.read(pc + 2);
+  uint8 p2 = bus.read(pc + 3);
+
+  switch(opcode) {
+    case 0x00: return { "nop" };
+    case 0x05: return { "dec  b" };
+    case 0x06: return { "ld   b,$", hex<2>(p0) };
+    case 0x0d: return { "dec  c" };
+    case 0x0e: return { "ld   c,$", hex<2>(p0) };
+    case 0x20: return { "jp   nz,$", hex<2>(p0) };
+    case 0x21: return { "ld   hl,$", hex<2>(p1), hex<2>(p0) };
+    case 0x32: return { "ldd  (hl),a" };
+    case 0x3e: return { "ld   a,$", hex<2>(p0) };
+    case 0xaf: return { "xor  a" };
+    case 0xc3: return { "jp   $", hex<2>(p1), hex<2>(p0) };
+  }
+
+  return { "???? [", hex<2>(opcode), ",", hex<2>(p1), ",", hex<2>(p0), "]" };
+}
+
+#endif
diff --git a/gameboy/cpu/registers.hpp b/gameboy/cpu/core/registers.hpp
similarity index 88%
rename from gameboy/cpu/registers.hpp
rename to gameboy/cpu/core/registers.hpp
index 45c8cbf7..db4cb602 100755
--- a/gameboy/cpu/registers.hpp
+++ b/gameboy/cpu/core/registers.hpp
@@ -1,3 +1,15 @@
+enum {
+  A, F, AF,
+  B, C, BC,
+  D, E, DE,
+  H, L, HL,
+  SP, PC,
+};
+
+enum {
+  ZF, NF, HF, CF,
+};
+
 //register base class
 //the idea here is to have all registers derive from a single base class.
 //this allows construction of opcodes that can take any register as input or output,
@@ -36,6 +48,10 @@ struct RegisterF : Register {
   bool z, n, h, c;
   operator unsigned() const { return (z << 7) | (n << 6) | (h << 5) | (c << 4); }
   unsigned operator=(unsigned x) { z = x & 0x80; n = x & 0x40; h = x & 0x20; c = x & 0x10; return *this; }
+  bool& operator[](unsigned r) {
+    static bool* table[] = { &z, &n, &h, &c };
+    return *table[r];
+  }
 };
 
 struct Register16 : Register {
@@ -75,5 +91,10 @@ struct Registers {
   Register16 sp;
   Register16 pc;
 
+  Register& operator[](unsigned r) {
+    static Register* table[] = { &a, &f, &af, &b, &c, &bc, &d, &e, &de, &h, &l, &hl, &sp, &pc };
+    return *table[r];
+  }
+
   Registers() : af(a, f), bc(b, c), de(d, e), hl(h, l) {}
 } r;
diff --git a/gameboy/cpu/cpu.cpp b/gameboy/cpu/cpu.cpp
index 2a986aec..b0646f32 100755
--- a/gameboy/cpu/cpu.cpp
+++ b/gameboy/cpu/cpu.cpp
@@ -1,18 +1,24 @@
-//Sharp LR35902 @ 4.19MHz
-
 #include <gameboy.hpp>
 
 #define CPU_CPP
 namespace GameBoy {
 
+#include "core/core.cpp"
+#include "timing/timing.cpp"
 CPU cpu;
 
+void CPU::Main() {
+  cpu.main();
+}
+
 void CPU::main() {
   while(true) {
-    uint8 opcode = bus.read(r.pc++);
-    switch(opcode) {
-      case 0x00: break;  //NOP
-    }
+    print(disassemble(r[PC]), "\n");
+
+    uint8 opcode = op_read(r[PC]++);
+    (this->*opcode_table[opcode])();
+
+    opcode_counter++;
   }
 }
 
@@ -21,7 +27,20 @@ void CPU::power() {
 }
 
 void CPU::reset() {
-  r.pc = 0x0100;
+  create(Main, 4 * 1024 * 1024);
+
+  r[PC] = 0x0100;
+  r[SP] = 0xfffe;
+  r[AF] = 0x0000;
+  r[BC] = 0x0000;
+  r[DE] = 0x0000;
+  r[HL] = 0x0000;
+
+  status.lycounter = 0;
+}
+
+CPU::CPU() {
+  initialize_opcode_table();
 }
 
 }
diff --git a/gameboy/cpu/cpu.hpp b/gameboy/cpu/cpu.hpp
index 073d12c9..fa28f0c3 100755
--- a/gameboy/cpu/cpu.hpp
+++ b/gameboy/cpu/cpu.hpp
@@ -1,10 +1,16 @@
-class CPU {
-public:
-  #include "registers.hpp"
+struct CPU : Processor {
+  #include "core/core.hpp"
+  #include "timing/timing.hpp"
 
+  struct Status {
+    unsigned lycounter;
+  } status;
+
+  static void Main();
   void main();
   void power();
   void reset();
+  CPU();
 };
 
 extern  CPU cpu;
diff --git a/gameboy/cpu/timing/opcode.cpp b/gameboy/cpu/timing/opcode.cpp
new file mode 100755
index 00000000..b952e3d6
--- /dev/null
+++ b/gameboy/cpu/timing/opcode.cpp
@@ -0,0 +1,18 @@
+#ifdef CPU_CPP
+
+void CPU::op_io() {
+  add_clocks(4);
+}
+
+uint8 CPU::op_read(uint16 addr) {
+  uint8 r = bus.read(addr);
+  add_clocks(4);
+  return r;
+}
+
+void CPU::op_write(uint16 addr, uint8 data) {
+  bus.write(addr, data);
+  add_clocks(4);
+}
+
+#endif
diff --git a/gameboy/cpu/timing/timing.cpp b/gameboy/cpu/timing/timing.cpp
new file mode 100755
index 00000000..becf6feb
--- /dev/null
+++ b/gameboy/cpu/timing/timing.cpp
@@ -0,0 +1,28 @@
+//4194304hz (4 * 1024 * 1024)
+//70224 clocks/frame
+//  456 clocks/scanline
+//  154 scanlines/frame
+
+#ifdef CPU_CPP
+
+#include "opcode.cpp"
+
+void CPU::add_clocks(unsigned clocks) {
+  clock += clocks;
+
+  if(clock >= 456) scanline();
+}
+
+void CPU::scanline() {
+  clock -= 456;
+
+  status.lycounter++;
+  if(status.lycounter >= 154) frame();
+}
+
+void CPU::frame() {
+  status.lycounter -= 154;
+  scheduler.exit();
+}
+
+#endif
diff --git a/gameboy/cpu/timing/timing.hpp b/gameboy/cpu/timing/timing.hpp
new file mode 100755
index 00000000..89dbf7d8
--- /dev/null
+++ b/gameboy/cpu/timing/timing.hpp
@@ -0,0 +1,8 @@
+void add_clocks(unsigned clocks);
+void scanline();
+void frame();
+
+//opcode.cpp
+void op_io();
+uint8 op_read(uint16 addr);
+void op_write(uint16 addr, uint8 data);
diff --git a/gameboy/gameboy.hpp b/gameboy/gameboy.hpp
index 917ea17c..c9c6948b 100755
--- a/gameboy/gameboy.hpp
+++ b/gameboy/gameboy.hpp
@@ -5,7 +5,7 @@
 namespace GameBoy {
   namespace Info {
     static const char Name[] = "bgameboy";
-    static const char Version[] = "000";
+    static const char Version[] = "000.01";
   }
 }
 
@@ -28,7 +28,23 @@ namespace GameBoy {
   typedef uint32_t uint32;
   typedef uint64_t uint64;
 
+  struct Processor {
+    cothread_t thread;
+    unsigned frequency;
+    int64 clock;
+
+    inline void create(void (*entrypoint_)(), unsigned frequency_) {
+      if(thread) co_delete(thread);
+      thread = co_create(65536 * sizeof(void*), entrypoint_);
+      frequency = frequency_;
+      clock = 0;
+    }
+
+    inline Processor() : thread(0) {}
+  };
+
   #include <system/system.hpp>
+  #include <scheduler/scheduler.hpp>
   #include <cartridge/cartridge.hpp>
   #include <memory/memory.hpp>
   #include <cpu/cpu.hpp>
diff --git a/gameboy/scheduler/scheduler.cpp b/gameboy/scheduler/scheduler.cpp
new file mode 100755
index 00000000..e8a98068
--- /dev/null
+++ b/gameboy/scheduler/scheduler.cpp
@@ -0,0 +1,33 @@
+#include <gameboy.hpp>
+
+#define SCHEDULER_CPP
+namespace GameBoy {
+
+Scheduler scheduler;
+
+void Scheduler::enter() {
+  host_thread = co_active();
+  co_switch(active_thread);
+}
+
+void Scheduler::exit() {
+  active_thread = co_active();
+  co_switch(host_thread);
+}
+
+void Scheduler::swapto(Processor &p) {
+  active_thread = p.thread;
+  co_switch(active_thread);
+}
+
+void Scheduler::init() {
+  host_thread = co_active();
+  active_thread = cpu.thread;
+}
+
+Scheduler::Scheduler() {
+  host_thread = 0;
+  active_thread = 0;
+}
+
+}
diff --git a/gameboy/scheduler/scheduler.hpp b/gameboy/scheduler/scheduler.hpp
new file mode 100755
index 00000000..69337acf
--- /dev/null
+++ b/gameboy/scheduler/scheduler.hpp
@@ -0,0 +1,13 @@
+struct Scheduler {
+  cothread_t host_thread;
+  cothread_t active_thread;
+
+  void enter();
+  void exit();
+  void swapto(Processor&);
+
+  void init();
+  Scheduler();
+};
+
+extern Scheduler scheduler;
diff --git a/gameboy/system/system.cpp b/gameboy/system/system.cpp
index bebae611..2a8b0aa1 100755
--- a/gameboy/system/system.cpp
+++ b/gameboy/system/system.cpp
@@ -11,10 +11,16 @@ void System::init(Interface *interface_) {
 
 void System::power() {
   cpu.power();
+  scheduler.init();
 }
 
 void System::reset() {
   cpu.reset();
+  scheduler.init();
+}
+
+void System::run() {
+  scheduler.enter();
 }
 
 }
diff --git a/gameboy/system/system.hpp b/gameboy/system/system.hpp
index ccc9b9c0..ccc6c889 100755
--- a/gameboy/system/system.hpp
+++ b/gameboy/system/system.hpp
@@ -5,6 +5,7 @@ public:
   void init(Interface*);
   void power();
   void reset();
+  void run();
 
 //private:
   Interface *interface;
diff --git a/ui/main.cpp b/ui/main.cpp
index 04a697c8..8aace5a4 100755
--- a/ui/main.cpp
+++ b/ui/main.cpp
@@ -16,6 +16,10 @@ void Application::main(int argc, char **argv) {
 
   while(quit == false) {
     OS::run();
+
+    if(GameBoy::cartridge.loaded()) {
+      GameBoy::system.run();
+    }
   }
 }