diff --git a/src/apu.h b/src/apu.h
index 5e0f9da..3da9107 100644
--- a/src/apu.h
+++ b/src/apu.h
@@ -16,9 +16,7 @@
 #define APU_ERR ERR_LOG
 
 
-#define nes_apu_frame_period = 7450;
-
-typedef enum {
+typedef enum  __attribute__ ((__packed__)) {
     apu_Status_Square_0  = 0b00000001,
     apu_Status_Square_1  = 0b00000010,
     apu_Status_Triangle  = 0b00000100,
@@ -85,9 +83,15 @@ typedef enum {
     apu_Channel_Start   = 0b00000010,
 } nes_apu_Channel_Flag;
 
+#define nes_apu_reg_base    (0x4000U)
+#define nes_apu_chan_count  (5U)
+#define nes_apu_chan_size   (4U)
+#define nes_apu_reg_status  (0x4015U)
+#define nes_apu_reg_frame   (0x4017U)
+
 typedef struct nes_apu_Channel_t {
     uint8_t reg[4];
-    void(*write)(struct nes_apu_Channel_t*, int reg, uint8_t);
+
     int gain;
     int length; // Active counter
     int delay;  // Cycles until next state change
@@ -125,13 +129,11 @@ typedef struct nes_apu_Channel_t {
             uint16_t addr;
         };
     };
+
+    void(*write)(struct nes_apu_Channel_t*, int reg, uint8_t);
 } nes_apu_Channel;
 
 typedef struct {
-    nes_apu_Channel channels[5];
-    uint8_t (*mem_read)(void*, uint16_t);
-    void* arg_mem;
-    struct blip_t* blip;
     nes_apu_Status status;
     uint8_t frame_reg;
     int frame;
@@ -139,6 +141,12 @@ typedef struct {
     int frame_period;
     int time;
     int frame_time_elapsed;
+
+    nes_apu_Channel channels[nes_apu_chan_count];
+
+    uint8_t (*mem_read)(void*, uint16_t);
+    void* arg_mem;
+    struct blip_t* blip;
 } nes_apu;
 
 typedef enum {
@@ -146,12 +154,6 @@ typedef enum {
     apu_Result_IRQ,
 } nes_apu_Result;
 
-#define nes_apu_reg_base    (0x4000U)
-#define nes_apu_chan_count  (5U)
-#define nes_apu_chan_size   (4U)
-#define nes_apu_reg_status  (0x4015U)
-#define nes_apu_reg_frame   (0x4017U)
-
 int nes_apu_init(nes_apu*, int clock, int frequency,
                  uint8_t(*)(void*, uint16_t), void*);
 void nes_apu_done(nes_apu*);
diff --git a/src/cart.c b/src/cart.c
index 043f937..4f912fa 100644
--- a/src/cart.c
+++ b/src/cart.c
@@ -90,7 +90,7 @@ int nes_cart_init_file(nes_cart* cart, FILE* file) {
 
     // Map file
     if (0 == status) {
-        mem = map_file(file, size);
+        mem = map_file(file, size, Filemap_Mode_Read);
         if (NULL == mem) {
             INES_ERR("Failed to map file (%d bytes)", size);
             status = -1;
diff --git a/src/filemap.h b/src/filemap.h
index 2a27222..e1349ef 100644
--- a/src/filemap.h
+++ b/src/filemap.h
@@ -2,7 +2,13 @@
 #define NESE_FILEMAP_H_
 
 
-void* map_file(FILE* file, int size);
+typedef enum {
+    Filemap_Mode_Read   = 0,
+    Filemap_Mode_Write,
+} Filemap_Mode;
+
+
+void* map_file(FILE* file, int size, Filemap_Mode);
 
 void unmap_file(void* mem, int size);
 
diff --git a/src/input.h b/src/input.h
index 6b331a8..e954f34 100644
--- a/src/input.h
+++ b/src/input.h
@@ -12,6 +12,8 @@ typedef enum {
     input_Result_OK     = 0,
     input_Result_Quit   = 1,
     input_Result_Reset  = 2,
+    input_Result_Save   = 3,
+    input_Result_Load   = 4,
 } nes_Input_Result;
 
 #define nes_controller_num_buttons  (8U)
diff --git a/src/linux/filemap.c b/src/linux/filemap.c
index 7dd2e16..c88c31b 100644
--- a/src/linux/filemap.c
+++ b/src/linux/filemap.c
@@ -1,3 +1,4 @@
+#include <errno.h>
 #include <stdio.h>
 
 #include <sys/mman.h>
@@ -5,9 +6,17 @@
 #include "filemap.h"
 
 
-void* map_file(FILE* file, int size) {
-    return mmap(NULL, size, PROT_READ, MAP_PRIVATE,
-                fileno(file), 0);
+void* map_file(FILE* file, int size, Filemap_Mode map_mode) {
+    int prot = (    Filemap_Mode_Write == map_mode ?
+                    PROT_WRITE : PROT_READ);
+    int flags = (   Filemap_Mode_Write == map_mode ?
+                    MAP_SHARED : MAP_PRIVATE);
+    void* mem = mmap(NULL, size, prot, flags, fileno(file), 0);
+    if ((void*)-1 == mem) {
+        fprintf(stderr, "Failed to map file: %d\n", errno);
+        mem = NULL;
+    }
+    return mem;
 }
 
 void unmap_file(void* mem, int size) {
diff --git a/src/map/cnrom.c b/src/map/cnrom.c
index e9c63ba..d7ee707 100644
--- a/src/map/cnrom.c
+++ b/src/map/cnrom.c
@@ -1,4 +1,5 @@
 #include <stdlib.h>
+#include <string.h>
 
 #include "map.h"
 
@@ -9,15 +10,23 @@ typedef struct {
     uint8_t* chr_rom;
     int chr_rom_banks;
     uint8_t mirror;
+
+    uint32_t bank;
     uint8_t vram[nes_vram_page_size * 2];
 
     uint8_t* chr_bank;
 } cnrom_mapper;
 
+static void cnrom_set_bank(cnrom_mapper* map, uint8_t bank) {
+    map->bank = (bank % map->chr_rom_banks);
+    map->chr_bank = &map->chr_rom[
+            map->bank * (nes_chr_page_size * 2)
+        ];
+}
 
 static void cnrom_reset(nes_mapper* nes_map) {
     cnrom_mapper* map = (cnrom_mapper*)nes_map->data;
-    map->chr_bank = 0;
+    cnrom_set_bank(map, 0);
 }
 
 static int cnrom_init(nes_mapper* nes_map, nes_cart* cart) {
@@ -60,8 +69,7 @@ static void cnrom_write(nes_mapper* nes_map,
                         uint16_t addr, uint8_t val) {
     cnrom_mapper* map = (cnrom_mapper*)nes_map->data;
     if (addr >= nes_mem_rom_start) {
-        map->chr_bank = &map->chr_rom[(val % map->chr_rom_banks) *
-                                      (nes_chr_page_size * 2)];
+        cnrom_set_bank(map, val);
     }
 }
 
@@ -84,6 +92,41 @@ static void cnrom_chr_write(nes_mapper* nes_map,
     // ROM only.
 }
 
+
+/* Save State */
+
+int cnrom_state_size(const nes_mapper* nes_map) {
+    cnrom_mapper* map = (cnrom_mapper*)nes_map->data;
+    return (sizeof(map->bank) + sizeof(map->vram));
+}
+
+int cnrom_state_read(nes_mapper* nes_map, const void* data) {
+    cnrom_mapper* map = (cnrom_mapper*)nes_map->data;
+    const void* ptr = data;
+
+    memcpy(&map->bank, ptr, sizeof(map->bank));
+    ptr += sizeof(map->bank);
+
+    memcpy(map->vram, ptr, sizeof(map->vram));
+    ptr += sizeof(map->vram);
+
+    return (ptr - data);
+}
+
+int cnrom_state_write(const nes_mapper* nes_map, void* data) {
+    cnrom_mapper* map = (cnrom_mapper*)nes_map->data;
+    void* ptr = data;
+
+    memcpy(ptr, &map->bank, sizeof(map->bank));
+    ptr += sizeof(map->bank);
+
+    memcpy(ptr, map->vram, sizeof(map->vram));
+    ptr += sizeof(map->vram);
+
+    return (ptr - data);
+}
+
+
 nes_mapper mapper_cnrom = {
     .name = "CNROM",
     .init = cnrom_init,
@@ -94,4 +137,8 @@ nes_mapper mapper_cnrom = {
     .chr_addr = cnrom_chr_addr,
     .vram_addr = cnrom_vram_addr,
     .chr_write = cnrom_chr_write,
+
+    .state_size = cnrom_state_size,
+    .state_read = cnrom_state_read,
+    .state_write = cnrom_state_write,
 };
diff --git a/src/map/mmc1.c b/src/map/mmc1.c
index 8c9ee14..302a9f7 100644
--- a/src/map/mmc1.c
+++ b/src/map/mmc1.c
@@ -1,4 +1,5 @@
 #include <stdlib.h>
+#include <string.h>
 
 #include "map.h"
 
@@ -11,6 +12,12 @@ typedef struct {
 
     uint8_t battery;
 
+    uint8_t* chr_bank[2];
+    uint8_t* vram_bank[4];
+    uint8_t* prg_bank[2];
+    uint8_t* chr_ram;
+    uint8_t* chr;
+
     uint8_t reg_shift;
     uint8_t reg_n_shift;
     uint8_t reg_control;
@@ -18,13 +25,6 @@ typedef struct {
     uint8_t reg_chr_1;
     uint8_t reg_prg;
 
-    uint8_t* chr_bank[2];
-    uint8_t* vram_bank[4];
-    uint8_t* prg_bank[2];
-
-    uint8_t* chr_ram;
-    uint8_t* chr;
-
     uint8_t vram[2][nes_vram_page_size];
     uint8_t wram[nes_mem_wram_size];
 } mmc1_mapper;
@@ -235,6 +235,30 @@ static int mmc1_sram_size(nes_mapper* nes_map) {
 }
 
 
+/* Save State */
+
+int mmc1_state_size(const nes_mapper* nes_map) {
+    mmc1_mapper* map = (mmc1_mapper*)nes_map->data;
+    return (    (void*)map +
+                sizeof(*map) -
+                (void*)&(map->reg_shift));
+}
+
+int mmc1_state_read(nes_mapper* nes_map, const void* data) {
+    mmc1_mapper* map = (mmc1_mapper*)nes_map->data;
+    int size = mmc1_state_size(nes_map);
+    memcpy(&(map->reg_shift), data, size);
+    return size;
+}
+
+int mmc1_state_write(const nes_mapper* nes_map, void* data) {
+    mmc1_mapper* map = (mmc1_mapper*)nes_map->data;
+    int size = mmc1_state_size(nes_map);
+    memcpy(data, &(map->reg_shift), size);
+    return size;
+}
+
+
 nes_mapper mapper_mmc1 = {
     .name = "MMC1",
     .init = mmc1_init,
@@ -248,4 +272,8 @@ nes_mapper mapper_mmc1 = {
 
     .sram_size = mmc1_sram_size,
     .sram = mmc1_sram,
+
+    .state_size = mmc1_state_size,
+    .state_read = mmc1_state_read,
+    .state_write = mmc1_state_write,
 };
diff --git a/src/map/mmc3.c b/src/map/mmc3.c
index 397276d..be5a34d 100644
--- a/src/map/mmc3.c
+++ b/src/map/mmc3.c
@@ -1,4 +1,5 @@
 #include <stdlib.h>
+#include <string.h>
 
 #include "map.h"
 
@@ -29,7 +30,7 @@ typedef struct {
     uint8_t* vram_bank[4];
 
     uint8_t r[8];
-    mmc3_Flag flags;
+    uint8_t flags;
     uint8_t bank_select;
     uint8_t irq_count;
     uint8_t irq_latch;
@@ -106,7 +107,7 @@ static inline void mmc3_update_chr(mmc3_mapper* map,
 }
 
 static inline void mmc3_update_rom_mode(mmc3_mapper* map, int val) {
-    uint8_t delta = map->bank_select ^ val;
+    uint8_t delta = (map->bank_select ^ val);
 
     map->bank_select = val;
 
@@ -119,7 +120,6 @@ static inline void mmc3_update_rom_mode(mmc3_mapper* map, int val) {
             mmc3_map_prg(map, 0, map->prg_rom_banks - 2);
             mmc3_map_prg(map, 2, map->r[6]);
         }
-
     }
 
     if (delta & mmc3_Bank_Select_CHR) {
@@ -344,6 +344,30 @@ static int mmc3_sram_size(nes_mapper* nes_map) {
 }
 
 
+/* Save State */
+
+int mmc3_state_size(const nes_mapper* nes_map) {
+    mmc3_mapper* map = (mmc3_mapper*)nes_map->data;
+    return (    (map->wram - map->r) +
+                sizeof(map->wram) +
+                sizeof(map->vram));
+}
+
+int mmc3_state_read(nes_mapper* nes_map, const void* data) {
+    mmc3_mapper* map = (mmc3_mapper*)nes_map->data;
+    int size = mmc3_state_size(nes_map);
+    memcpy(map->r, data, size);
+    return size;
+}
+
+int mmc3_state_write(const nes_mapper* nes_map, void* data) {
+    mmc3_mapper* map = (mmc3_mapper*)nes_map->data;
+    int size = mmc3_state_size(nes_map);
+    memcpy(data, map->r, size);
+    return size;
+}
+
+
 nes_mapper mapper_mmc3 = {
     .name = "MMC3",
     .init = mmc3_init,
@@ -358,4 +382,8 @@ nes_mapper mapper_mmc3 = {
 
     .sram_size = mmc3_sram_size,
     .sram = mmc3_sram,
+
+    .state_size = mmc3_state_size,
+    .state_read = mmc3_state_read,
+    .state_write = mmc3_state_write,
 };
diff --git a/src/map/nrom.c b/src/map/nrom.c
index d1aba8f..526d9ca 100644
--- a/src/map/nrom.c
+++ b/src/map/nrom.c
@@ -1,4 +1,5 @@
 #include <stdlib.h>
+#include <string.h>
 
 #include "map.h"
 
@@ -97,6 +98,29 @@ static void nrom_chr_write(nes_mapper* nes_map,
 //    printf("CHR ROM Write: $%04x < %02x\n", addr, val);
 }
 
+
+/* Save State */
+
+int nrom_state_size(const nes_mapper* nes_map) {
+    nrom_mapper* map = (nrom_mapper*)nes_map->data;
+    return (sizeof(map->vram) + sizeof(map->wram));
+}
+
+int nrom_state_read(nes_mapper* nes_map, const void* data) {
+    nrom_mapper* map = (nrom_mapper*)nes_map->data;
+    memcpy(map->vram, data, sizeof(map->vram));
+    memcpy(map->wram, data + sizeof(map->vram), sizeof(map->wram));
+    return (sizeof(map->vram) + sizeof(map->wram));
+}
+
+int nrom_state_write(const nes_mapper* nes_map, void* data) {
+    nrom_mapper* map = (nrom_mapper*)nes_map->data;
+    memcpy(data, map->vram, sizeof(map->vram));
+    memcpy(data + sizeof(map->vram), map->wram, sizeof(map->wram));
+    return (sizeof(map->vram) + sizeof(map->wram));
+}
+
+
 nes_mapper mapper_nrom = {
     .name = "NROM",
     .init = nrom_init,
@@ -107,4 +131,8 @@ nes_mapper mapper_nrom = {
     .chr_addr = nrom_chr_addr,
     .vram_addr = nrom_vram_addr,
     .chr_write = nrom_chr_write,
+
+    .state_size = nrom_state_size,
+    .state_read = nrom_state_read,
+    .state_write = nrom_state_write,
 };
diff --git a/src/map/uxrom.c b/src/map/uxrom.c
index 3986a34..45c7de1 100644
--- a/src/map/uxrom.c
+++ b/src/map/uxrom.c
@@ -1,4 +1,5 @@
 #include <stdlib.h>
+#include <string.h>
 
 #include "map.h"
 
@@ -7,6 +8,8 @@ typedef struct {
     uint8_t* prg_rom;
     int prg_rom_banks;
     uint8_t mirror;
+
+    uint8_t bank;
     uint8_t vram[nes_vram_page_size * 2];
     uint8_t chr_ram[8 * 1024];
 
@@ -14,9 +17,16 @@ typedef struct {
     uint8_t* prg_bank_hi;
 } uxrom_mapper;
 
+static void uxrom_set_bank(uxrom_mapper* map, uint8_t bank) {
+    map->bank = (bank % map->prg_rom_banks);
+    map->prg_bank_lo = &map->prg_rom[
+            map->bank * nes_prg_rom_page_size
+        ];
+}
 
 static void uxrom_reset(nes_mapper* nes_map) {
     uxrom_mapper* map = (uxrom_mapper*)nes_map->data;
+    uxrom_set_bank(map, 0);
     map->prg_bank_lo = map->prg_rom;
 }
 
@@ -58,10 +68,7 @@ static void uxrom_write(nes_mapper* nes_map,
                         uint16_t addr, uint8_t val) {
     uxrom_mapper* map = (uxrom_mapper*)nes_map->data;
     if (addr >= nes_mem_rom_start) {
-        map->prg_bank_lo = &map->prg_rom[
-                (val % map->prg_rom_banks) *
-                nes_prg_rom_page_size
-            ];
+        uxrom_set_bank(map, val);
     }
 }
 
@@ -84,6 +91,50 @@ static void uxrom_chr_write(nes_mapper* nes_map,
     ((uxrom_mapper*)nes_map->data)->chr_ram[addr] = val;
 }
 
+
+/* Save State */
+
+int uxrom_state_size(const nes_mapper* nes_map) {
+    uxrom_mapper* map = (uxrom_mapper*)nes_map->data;
+    return (    sizeof(uint32_t) +
+                sizeof(map->vram) +
+                sizeof(map->chr_ram));
+}
+
+int uxrom_state_read(nes_mapper* nes_map, const void* data) {
+    uxrom_mapper* map = (uxrom_mapper*)nes_map->data;
+    const void* ptr = data;
+
+    map->bank = *(uint32_t*)ptr;
+    ptr += sizeof(uint32_t);
+
+    memcpy(map->vram, ptr, sizeof(map->vram));
+    ptr += sizeof(map->vram);
+
+    memcpy(map->chr_ram, ptr, sizeof(map->chr_ram));
+    ptr += sizeof(map->chr_ram);
+
+    return (ptr - data);
+}
+
+int uxrom_state_write(const nes_mapper* nes_map, void* data) {
+    uxrom_mapper* map = (uxrom_mapper*)nes_map->data;
+    void* ptr = data;
+
+    uint32_t bank = map->bank;
+    memcpy(ptr, &bank, sizeof(bank));
+    ptr += sizeof(bank);
+
+    memcpy(ptr, map->vram, sizeof(map->vram));
+    ptr += sizeof(map->vram);
+
+    memcpy(ptr, map->chr_ram, sizeof(map->chr_ram));
+    ptr += sizeof(map->chr_ram);
+
+    return (ptr - data);
+}
+
+
 nes_mapper mapper_uxrom = {
     .name  = "UxROM",
     .init  = uxrom_init,
@@ -94,4 +145,8 @@ nes_mapper mapper_uxrom = {
     .chr_addr  = uxrom_chr_addr,
     .vram_addr = uxrom_vram_addr,
     .chr_write = uxrom_chr_write,
+
+    .state_size = uxrom_state_size,
+    .state_read = uxrom_state_read,
+    .state_write = uxrom_state_write,
 };
diff --git a/src/mapper.h b/src/mapper.h
index deef8e5..6d53c1e 100644
--- a/src/mapper.h
+++ b/src/mapper.h
@@ -34,8 +34,9 @@ typedef struct nes_mapper_t {
     void* (*sram)(struct nes_mapper_t*);
     int (*sram_size)(struct nes_mapper_t*);
 
-    void (*save)(struct nes_mapper_t**);
-    int (*save_size)(struct nes_mapper_t*);
+    int (*state_size)(const struct nes_mapper_t*);
+    int (*state_read)(struct nes_mapper_t*, const void*);
+    int (*state_write)(const struct nes_mapper_t*, void*);
 
 } nes_mapper;
 
diff --git a/src/nese.c b/src/nese.c
index a19c749..b282abf 100644
--- a/src/nese.c
+++ b/src/nese.c
@@ -99,7 +99,6 @@ int main(int argc, char* argv[]) {
                     t_target += elapsed_us;
 
                     time_us slept_us = time_sleep_until(t_target);
-                    (void)slept_us;
 
                     if (slept_us <= -elapsed_us) {
                         // We're way out of sync.
@@ -114,6 +113,14 @@ int main(int argc, char* argv[]) {
                     if (input_Result_Reset == status) {
                         nes_reset(&sys);
                         status = 0;
+
+                    } else if (input_Result_Load == status) {
+                        load_state(&sys, cart_filename);
+                        status = 0;
+
+                    } else if (input_Result_Save == status) {
+                        save_state(&sys, cart_filename);
+                        status = 0;
                     }
 
                     if (status == 0) {
diff --git a/src/ppu.h b/src/ppu.h
index baef699..12a4acb 100644
--- a/src/ppu.h
+++ b/src/ppu.h
@@ -122,7 +122,6 @@ typedef enum {
 
 typedef struct {
     // Memory
-    struct nes_mapper_t* mapper;
     oam_sprite oam[nes_ppu_oam_sprite_count];
     uint8_t palette[nes_ppu_mem_pal_size];
 
@@ -134,6 +133,9 @@ typedef struct {
     int hit_line;
     int hit_dot;
 
+    // Internal Registers
+    uint8_t latch;
+
     // External registers
     uint8_t control;
     uint8_t mask;
@@ -147,9 +149,8 @@ typedef struct {
     uint8_t data;
     uint8_t oam_addr;
 
-    // Internal Registers
-    uint8_t latch;
-
+    // System Interface
+    struct nes_mapper_t* mapper;
 } nes_ppu;
 
 uint8_t nes_ppu_read(nes_ppu* ppu, uint16_t addr);
diff --git a/src/save.c b/src/save.c
index a9760f5..c62a7cc 100644
--- a/src/save.c
+++ b/src/save.c
@@ -1,7 +1,13 @@
+#include <inttypes.h>
+#include <string.h>
+
 #include "save.h"
 #include "file.h"
 #include "mapper.h"
+#include "filemap.h"
+
 
+/* SRAM */
 
 static int make_sram_filename(char* sram_filename, int max_len,
                               const char* cart_filename) {
@@ -45,3 +51,339 @@ int save_sram(const nes_cart* cart, const char* cart_filename) {
 
     return status;
 }
+
+
+/* System State */
+
+static int make_state_filename(char* sram_filename, int max_len,
+                               const char* cart_filename) {
+    return make_filename(  sram_filename, max_len,
+                           basename(cart_filename),
+                           "save", "nese");
+}
+
+int load_state(nes* sys, const char* cart_filename) {
+    int size = -1;
+
+    char state_filename[FILENAME_MAX] = {0};
+    make_state_filename(state_filename, FILENAME_MAX - 1,
+                        cart_filename);
+
+    FILE* file = fopen(state_filename, "rb");
+
+    if (NULL != file) {
+        int file_size = state_size(sys);
+        void* mem = map_file(file, file_size, Filemap_Mode_Read);
+
+        if (NULL != mem) {
+            size = state_read(sys, mem, file_size);
+            unmap_file(mem, file_size);
+        }
+
+        fclose(file);
+    }
+
+    return size;
+}
+
+int save_state(const nes* sys, const char* cart_filename) {
+    int size = -1;
+
+    char state_filename[FILENAME_MAX] = {0};
+    make_state_filename(state_filename, FILENAME_MAX - 1,
+                        cart_filename);
+
+    FILE* file = fopen(state_filename, "w+b");
+
+    if (NULL != file) {
+        int file_size = state_size(sys);
+
+        fseek(file, file_size - 1, SEEK_SET);
+        fwrite("", 1, 1, file);
+        fflush(file);
+
+        void* mem = map_file(file, file_size, Filemap_Mode_Write);
+
+        if (NULL != mem) {
+            size = state_write(sys, mem, file_size);
+            unmap_file(mem, file_size);
+        }
+
+        fclose(file);
+    }
+
+    return size;
+}
+
+
+#define tag_def(X)  ( \
+        X[0] | (X[1] << 8) | (X[2] << 16) | (X[3] << 24) \
+    )
+
+#define tag_NESE    tag_def("NESE")
+#define tag_cpu     tag_def("tCPU")
+#define tag_ppu     tag_def("tPPU")
+#define tag_apu     tag_def("tAPU")
+#define tag_ram     tag_def("WRAM")
+#define tag_mapper  tag_def("MAPP")
+
+
+#define szChunkTag      sizeof(uint32_t)
+#define szChunkHeader   (szChunkTag + sizeof(uint32_t))
+
+
+static int cpu_state_size(const e6502_Core* core) {
+    return (sizeof(core->registers) + sizeof(core->pins));
+}
+
+static int cpu_state_read(e6502_Core* core, const void* mem) {
+    memcpy(&core->registers, mem, sizeof(core->registers));
+    memcpy(&core->pins, mem + sizeof(core->registers),
+           sizeof(core->pins));
+    return (sizeof(core->registers) + sizeof(core->pins));
+}
+
+static int cpu_state_write(const e6502_Core* core, void* mem) {
+    memcpy(mem, &core->registers, sizeof(core->registers));
+    memcpy(mem + sizeof(core->registers), &core->pins,
+           sizeof(core->pins));
+    return (sizeof(core->registers) + sizeof(core->pins));
+}
+
+
+static int ppu_state_size(const nes_ppu* ppu) {
+    return ((void*)&(ppu->mapper) - (void*)ppu);
+}
+
+static int ppu_state_read(nes_ppu* ppu, const void* mem) {
+    int size = ppu_state_size(ppu);
+    memcpy(ppu, mem, size);
+    return size;
+}
+
+static int ppu_state_write(const nes_ppu* ppu, void* mem) {
+    int size = ppu_state_size(ppu);
+    memcpy(mem, ppu, size);
+    return size;
+}
+
+
+static int apu_state_size(const nes_apu* apu) {
+    return (    ((void*)(apu->channels) - (void*)apu) +
+                (5 * (   (void*)&(apu->channels->write) -
+                        (void*)(apu->channels)
+                     )   )
+                );
+}
+
+static int apu_state_read(nes_apu* apu, const void* mem) {
+    int size = ((void*)(apu->channels) - (void*)apu);
+    memcpy(apu, mem, size);
+    const void* ptr = (mem + size);
+    size = (    (void*)&(apu->channels->write) -
+                (void*)(apu->channels));
+    for (int chan = 0; chan < nes_apu_chan_count; ++chan) {
+        memcpy(&apu->channels[chan], ptr, size);
+        ptr += size;
+    }
+    return (ptr - mem);
+}
+
+static int apu_state_write(const nes_apu* apu, void* mem) {
+    int size = ((void*)(apu->channels) - (void*)apu);
+    memcpy(mem, apu, size);
+    void* ptr = (mem + size);
+    size = (    (void*)&(apu->channels->write) -
+                (void*)(apu->channels));
+    for (int chan = 0; chan < nes_apu_chan_count; ++chan) {
+        memcpy(ptr, &apu->channels[chan], size);
+        ptr += size;
+    }
+    return (ptr - mem);
+}
+
+
+static int ram_state_size(const nes* sys) {
+    return sizeof(sys->ram);
+}
+
+static int ram_state_read(nes* sys, const void* mem) {
+    memcpy(sys->ram, mem, sizeof(sys->ram));
+    return sizeof(sys->ram);
+}
+
+static int ram_state_write(const nes* sys, void* mem) {
+    memcpy(mem, sys->ram, sizeof(sys->ram));
+    return sizeof(sys->ram);
+}
+
+
+int state_size(const nes* sys) {
+    int size = szChunkHeader;
+
+    size += szChunkHeader + cpu_state_size(&sys->cpu);
+    size += szChunkHeader + ppu_state_size(&sys->ppu);
+    size += szChunkHeader + apu_state_size(&sys->apu);
+    // Ignoring input
+    size += szChunkHeader + ram_state_size(sys);
+    // Cart should already be loaded
+    size += szChunkHeader +
+            sys->cart.mapper->state_size(sys->cart.mapper);
+
+    return size;
+}
+
+static inline void* write_header(void* mem,
+                                 uint32_t tag,
+                                 uint32_t size) {
+    memcpy(mem, &tag, szChunkTag);
+    mem += szChunkTag;
+    memcpy(mem, &size, sizeof(size));
+    mem += sizeof(size);
+    return mem;
+}
+
+static inline const void* read_header(const void* mem,
+                                      uint32_t* tag,
+                                      uint32_t* size) {
+    memcpy(tag, mem, szChunkTag);
+    mem += szChunkTag;
+    memcpy(size, mem, sizeof(size[0]));
+    mem += sizeof(size[0]);
+    return mem;
+}
+
+int state_write(const nes* sys, void* mem, int size) {
+    void* ptr = mem;
+
+    ptr = write_header(ptr, tag_NESE, state_size(sys));
+
+    ptr = write_header(ptr, tag_cpu, cpu_state_size(&sys->cpu));
+    ptr += cpu_state_write(&sys->cpu, ptr);
+
+    ptr = write_header(ptr, tag_ppu, ppu_state_size(&sys->ppu));
+    ptr += ppu_state_write(&sys->ppu, ptr);
+
+    ptr = write_header(ptr, tag_apu, apu_state_size(&sys->apu));
+    ptr += apu_state_write(&sys->apu, ptr);
+
+    ptr = write_header(ptr, tag_ram, ram_state_size(sys));
+    ptr += ram_state_write(sys, ptr);
+
+    const nes_mapper* mapper = sys->cart.mapper;
+    ptr = write_header(ptr, tag_mapper, mapper->state_size(mapper));
+    ptr += mapper->state_write(mapper, ptr);
+
+    return (ptr - mem);
+}
+
+typedef enum {
+    Component_CPU    = 0b00000001,
+    Component_PPU    = 0b00000010,
+    Component_APU    = 0b00000100,
+    Component_RAM    = 0b00001000,
+    Component_Mapper = 0b00010000,
+} nes_Component;
+
+int state_read(nes* sys, const void* mem, int mem_size) {
+    int result = 0;
+    nes_Component loaded = 0;
+
+    const void* ptr = mem;
+    const void* end = (mem + mem_size);
+
+    uint32_t tag = 0;
+    uint32_t size = 0;
+
+    ptr = read_header(mem, &tag, &size);
+    if (tag_NESE != tag) {
+        result = -1;
+        fprintf(stderr,
+                "Bad save state magic: %.4s\n",
+                (char*)&tag);
+    }
+
+    while (0 == result && ptr < end) {
+        ptr = read_header(ptr, &tag, &size);
+        if ((ptr + size) > end) {
+            result = -1;
+            fprintf(stderr,
+                    "Unusually large chunk: %.4s: +%"PRIu64"\n",
+                    (char*)&tag,
+                    ((ptr + size) - end));
+            break;
+        }
+
+        int n_read = 0;
+
+        if (tag_cpu == tag) {
+            n_read = cpu_state_read(&sys->cpu, ptr);
+            loaded |= Component_CPU;
+
+        } else if (tag_ppu == tag) {
+            n_read = ppu_state_read(&sys->ppu, ptr);
+            loaded |= Component_PPU;
+
+        } else if (tag_apu == tag) {
+            n_read = apu_state_read(&sys->apu, ptr);
+            loaded |= Component_APU;
+
+        } else if (tag_ram == tag) {
+            n_read = ram_state_read(sys, ptr);
+            loaded |= Component_RAM;
+
+        } else if (tag_mapper == tag) {
+            n_read = sys->cart.mapper->state_read(
+                    sys->cart.mapper, ptr
+                );
+            loaded |= Component_Mapper;
+
+        } else {
+            fprintf(stderr,
+                    "Strange chunk: %.4s\n",
+                    (char*)&tag);
+        }
+
+        if (n_read != size) {
+            result = -1;
+            fprintf(stderr,
+                    "Chunk %.4s: read %d, expected %d\n",
+                    (char*)&tag, n_read, size);
+        }
+
+        ptr += size;
+    }
+
+    if (0 == result) {
+        if (!(loaded | Component_CPU)) {
+            result = -1;
+            fprintf(stderr, "Missing %s state\n", "CPU");
+        }
+
+        if (!(loaded | Component_PPU)) {
+            result = -1;
+            fprintf(stderr, "Missing %s state\n", "PPU");
+        }
+
+        if (!(loaded | Component_APU)) {
+            result = -1;
+            fprintf(stderr, "Missing %s state\n", "APU");
+        }
+
+        if (!(loaded | Component_RAM)) {
+            result = -1;
+            fprintf(stderr, "Missing %s state\n", "RAM");
+        }
+
+        if (!(loaded | Component_Mapper)) {
+            result = -1;
+            fprintf(stderr, "Missing %s state\n", "Mapper");
+        }
+    }
+
+    if (0 == result) {
+        result = (ptr - mem);
+    }
+
+    return result;
+}
diff --git a/src/save.h b/src/save.h
index 7f5b310..ffff4b0 100644
--- a/src/save.h
+++ b/src/save.h
@@ -1,11 +1,18 @@
 #ifndef NESE_SAVE_H_
 #define NESE_SAVE_H_
 
-#include "cart.h"
+#include "nes.h"
 
 
 int load_sram(nes_cart* cart, const char* filename);
 int save_sram(const nes_cart* cart, const char* filename);
 
+int state_size(const nes*);
+int state_read(nes*, const void* mem, int size);
+int state_write(const nes*, void* mem, int size);
+
+int load_state(nes*, const char* filename);
+int save_state(const nes*, const char* filename);
+
 
 #endif // NESE_SAVE_H_
diff --git a/src/sdl_input.c b/src/sdl_input.c
index 53eb4b5..d852b94 100644
--- a/src/sdl_input.c
+++ b/src/sdl_input.c
@@ -5,7 +5,9 @@
 
 static SDL_GameController* sdl_find_gamepad() {
     int i = SDL_NumJoysticks() - 1;
+    printf("Found %d joysticks\n", i + 1);
     for ( ; i >= 0 && !SDL_IsGameController(i); --i);
+    if (i >= 0) printf("Joystick %d is a gamepad\n", i);
     return (i < 0 ? NULL : SDL_GameControllerOpen(i));
 }
 
@@ -52,6 +54,8 @@ static void sdl_input_done(nes_Input_Reader* input) {
 }
 
 static const int sdl_reset_key = SDLK_ESCAPE;
+static const int sdl_save_key = SDLK_F1;
+static const int sdl_load_key = SDLK_F2;
 
 static const int sdl_keycodes[nes_controller_num_buttons] = {
     SDLK_a,
@@ -102,9 +106,17 @@ static int sdl_input_update(nes_Input_Reader* reader,
                     input->controllers[0].buttons &= ~mask;
                 }
 
-            } else if ( event.key.keysym.sym == sdl_reset_key &&
+            } else if ( sdl_reset_key == event.key.keysym.sym &&
                         SDL_KEYDOWN == event.type) {
                 status = input_Result_Reset;
+
+            } else if ( sdl_save_key == event.key.keysym.sym &&
+                        SDL_KEYDOWN == event.type) {
+                status = input_Result_Save;
+
+            } else if ( sdl_load_key == event.key.keysym.sym &&
+                        SDL_KEYDOWN == event.type) {
+                status = input_Result_Load;
             }
 
         } else if ( SDL_CONTROLLERBUTTONDOWN == event.type ||
@@ -150,14 +162,22 @@ static int sdl_input_update(nes_Input_Reader* reader,
 
         } else if (SDL_CONTROLLERDEVICEADDED == event.type) {
             if (NULL == reader->data) {
+                printf("New gamepad connected\n");
                 reader->data = sdl_find_gamepad();
+                if (reader->data) printf("Using new gamepad\n");
+            } else {
+                printf("Redundant gamepad connected\n");
             }
 
         } else if (SDL_CONTROLLERDEVICEREMOVED == event.type) {
             if (sdl_match_gamepad(event.cdevice.which,
                                   reader->data)) {
+                printf("Gamepad disconnected\n");
                 sdl_lose_gamepad(reader->data);
                 reader->data = sdl_find_gamepad();
+                if (reader->data) printf("Using another gamepad\n");
+            } else {
+                printf("Redundant gamepad disconnected\n");
             }
         }
     }
diff --git a/src/win/filemap.c b/src/win/filemap.c
index a5a0959..3164437 100644
--- a/src/win/filemap.c
+++ b/src/win/filemap.c
@@ -47,17 +47,22 @@ static void store_map_handle(const void* mem, HANDLE handle) {
 }
 
 
-void* map_file(FILE* file, int size) {
+void* map_file(FILE* file, int size, Filemap_Mode map_mode) {
     void* mem = NULL;
 
+    DWORD protect = (   Filemap_Mode_Write == map_mode ?
+                        PAGE_READWRITE : PAGE_READONLY);
+    DWORD access = (    Filemap_Mode_Write == map_mode ?
+                        FILE_MAP_WRITE : FILE_MAP_READ);
+
     HANDLE hFile = (HANDLE)_get_osfhandle(fileno(file));
 
     HANDLE hMap = CreateFileMappingA(
-            hFile, 0, PAGE_READONLY, 0, size, 0
+            hFile, 0, protect, 0, size, 0
         );
 
     if (NULL != hMap) {
-        mem = MapViewOfFile(hMap, FILE_MAP_READ, 0, 0, size);
+        mem = MapViewOfFile(hMap, access, 0, 0, size);
         if (NULL == mem) {
             CloseHandle(hMap);
         } else {