diff --git a/include/apple2.h b/include/apple2.h
index c24eaae..f307022 100644
--- a/include/apple2.h
+++ b/include/apple2.h
@@ -103,11 +103,11 @@ typedef struct {
     mos6502 *cpu;
 
     /*
-     * This is the literal memory that the CPU above will create. You
-     * should _not_ attempt to free this memory; allow the CPU's own
-     * delete function to do that.
+     * This is the main memory bank of the computer. Conventionally, it
+     * contains not only the first contiguous 48k of RAM, but it also
+     * contains the last 12k of bank 1 RAM.
      */
-    vm_segment *memory;
+    vm_segment *main;
 
     /*
      * The Apple II used a system of bank-switched memory to enable
diff --git a/include/mos6502.h b/include/mos6502.h
index 03a43bb..68e68af 100644
--- a/include/mos6502.h
+++ b/include/mos6502.h
@@ -17,7 +17,7 @@
  * the PC register position; useful in testing.
  */
 #define SET_PC_BYTE(cpu, off, byte) \
-    vm_segment_set(cpu->memory, cpu->PC + off, byte)
+    mos6502_set(cpu, cpu->PC + off, byte)
 
 /*
  * This macro is used to define new instruction handler functions.
@@ -52,9 +52,13 @@
 
 typedef struct {
     /*
-     * Our memory.
+     * There are two different segment pointers for reading and writing,
+     * because it's possible for there to be two different banks in
+     * which an action occurs. These memory segments must be injected at
+     * creation time, and can be changed later.
      */
-    vm_segment *memory;
+    vm_segment *rmem;
+    vm_segment *wmem;
 
     /*
      * This contains the last _effective_ address we've resolved in one
@@ -116,14 +120,18 @@ typedef void (*mos6502_instruction_handler)(mos6502 *, vm_8bit);
 extern bool mos6502_would_jump(int);
 extern int mos6502_cycles(mos6502 *, vm_8bit);
 extern int mos6502_instruction(vm_8bit);
-extern mos6502 *mos6502_create();
+extern mos6502 *mos6502_create(vm_segment *, vm_segment *);
 extern mos6502_instruction_handler mos6502_get_instruction_handler(vm_8bit);
+extern vm_16bit mos6502_get16(mos6502 *, size_t);
 extern vm_16bit mos6502_pop_stack(mos6502 *);
+extern vm_8bit mos6502_get(mos6502 *, size_t);
 extern void mos6502_execute(mos6502 *);
 extern void mos6502_flash_memory(mos6502 *, vm_segment *);
 extern void mos6502_free(mos6502 *);
 extern void mos6502_modify_status(mos6502 *, vm_8bit, vm_8bit);
 extern void mos6502_push_stack(mos6502 *, vm_16bit);
+extern void mos6502_set(mos6502 *, size_t, vm_8bit);
+extern void mos6502_set16(mos6502 *, size_t, vm_16bit);
 extern void mos6502_set_status(mos6502 *, vm_8bit);
 
 /*
diff --git a/include/mos6502.tests.h b/include/mos6502.tests.h
index 705b4a3..d1c5f47 100644
--- a/include/mos6502.tests.h
+++ b/include/mos6502.tests.h
@@ -2,17 +2,20 @@
 #define _MOS6502_TESTS_H
 
 static mos6502 *cpu;
+static vm_segment *mem;
 
 static void
 setup()
 {
-    cpu = mos6502_create();
+    mem = vm_segment_create(MOS6502_MEMSIZE);
+    cpu = mos6502_create(mem, mem);
 }
 
 static void
 teardown()
 {
     mos6502_free(cpu);
+    vm_segment_free(mem);
 }
 
 #endif
diff --git a/src/apple2.c b/src/apple2.c
index 913d309..272ba4d 100644
--- a/src/apple2.c
+++ b/src/apple2.c
@@ -51,16 +51,20 @@ apple2_create(int width, int height)
     mach->drive1 = NULL;
     mach->drive2 = NULL;
 
-    mach->cpu = mos6502_create();
+    mach->main = vm_segment_create(MOS6502_MEMSIZE);
+    if (mach->main == NULL) {
+        log_critical("Could not initialize main RAM!");
+        apple2_free(mach);
+        return NULL;
+    }
+
+    mach->cpu = mos6502_create(mach->main, mach->main);
     if (mach->cpu == NULL) {
         log_critical("Could not create CPU!");
         apple2_free(mach);
         return NULL;
     }
 
-    // Our memory is that which is owned by the CPU.
-    mach->memory = mach->cpu->memory;
-
     // Set the read/write mappers for everything
     apple2_mem_map(mach);
 
@@ -194,15 +198,11 @@ apple2_boot(apple2 *mach)
 
     // To begin with, we need to set the reset vector to the Applesoft
     // interpeter.
-    vm_segment_set16(mach->memory, APPLE2_RESET_VECTOR,
+    vm_segment_set16(mach->main, APPLE2_RESET_VECTOR,
                      APPLE2_APPLESOFT_MAIN);
 
-    if (option_flag(OPTION_FLASH)) {
-        mos6502_flash_memory(mach->cpu, mach->drive1->data);
-    }
-
     if (option_flag(OPTION_DISASSEMBLE)) {
-        mos6502_dis_scan(mach->cpu, stdout, 0, mach->cpu->memory->size);
+        mos6502_dis_scan(mach->cpu, stdout, 0, mach->main->size);
     }
 
     // Run the reset routine to get the machine ready to go.
@@ -220,7 +220,7 @@ void
 apple2_reset(apple2 *mach)
 {
     mach->cpu->P = MOS_INTERRUPT;
-    mach->cpu->PC = vm_segment_get16(mach->memory, 0xFFFC);
+    mach->cpu->PC = vm_segment_get16(mach->main, 0xFFFC);
     mach->cpu->S = 0;
 
     // Switch video mode back to 40 column text
@@ -243,8 +243,8 @@ apple2_clear_strobe(apple2 *mach)
 {
     vm_8bit ch;
 
-    ch = vm_segment_get(mach->memory, LAST_KEY);
-    vm_segment_set(mach->memory, LAST_KEY, ch & 0x7F);
+    ch = vm_segment_get(mach->main, LAST_KEY);
+    vm_segment_set(mach->main, LAST_KEY, ch & 0x7F);
 }
 
 /*
@@ -303,13 +303,13 @@ apple2_press_key(apple2 *mach, vm_8bit ch)
 
     // This is the location in memory where a program will expect to
     // find the value of the last key that was pressed.
-    vm_segment_set(mach->memory, LAST_KEY, ch);
+    vm_segment_set(mach->main, LAST_KEY, ch);
 
     // This area is a combination of flags; the eighth bit here is the
     // "any-key-down" flag, which is a bit of a mouthful. It's 1 if a
     // key is pressed, and 0 if not. The effect of reading this bit will
     // also _clear_ the strobe bit in the $C000 address (above).
-    vm_segment_set(mach->memory, ANY_KEY_DOWN, 0x80);
+    vm_segment_set(mach->main, ANY_KEY_DOWN, 0x80);
 }
 
 /*
@@ -318,7 +318,7 @@ apple2_press_key(apple2 *mach, vm_8bit ch)
 void
 apple2_release_key(apple2 *mach)
 {
-    vm_segment_set(mach->memory, ANY_KEY_DOWN, 0);
+    vm_segment_set(mach->main, ANY_KEY_DOWN, 0);
 }
 
 /*
diff --git a/src/apple2.draw.c b/src/apple2.draw.c
index b68df89..9d6a815 100644
--- a/src/apple2.draw.c
+++ b/src/apple2.draw.c
@@ -50,7 +50,7 @@ apple2_draw_pixel(apple2 *mach, vm_16bit addr)
 void
 apple2_draw_pixel_lores(apple2 *mach, vm_16bit addr)
 {
-    vm_8bit color = vm_segment_get(mach->memory, addr);
+    vm_8bit color = vm_segment_get(mach->main, addr);
     vm_8bit top, bottom;
     vm_area loc;
     int *colors;
@@ -151,7 +151,7 @@ apple2_draw_text(apple2 *mach, vm_16bit addr)
     dest.height = mach->sysfont->height;
 
     // And...lastly...what's in the address?
-    ch = (char)vm_segment_get(mach->memory, addr);
+    ch = (char)vm_segment_get(mach->main, addr);
 
     // Let's firstly blank out that space on screen.
     vm_bitfont_render(mach->sysfont, mach->screen, &dest, ' ');
diff --git a/src/apple2.mem.c b/src/apple2.mem.c
index a6df9f7..c4d371f 100644
--- a/src/apple2.mem.c
+++ b/src/apple2.mem.c
@@ -83,8 +83,8 @@ apple2_mem_map(apple2 *mach)
     vm_segment_set_map_machine(mach);
 
     for (addr = APPLE2_BANK_OFFSET; addr < MOS6502_MEMSIZE; addr++) {
-        vm_segment_read_map(mach->memory, addr, apple2_mem_read_bank);
-        vm_segment_write_map(mach->memory, addr, apple2_mem_write_bank);
+        vm_segment_read_map(mach->main, addr, apple2_mem_read_bank);
+        vm_segment_write_map(mach->main, addr, apple2_mem_write_bank);
     }
 }
 
@@ -95,7 +95,7 @@ apple2_mem_init_peripheral_rom(apple2 *mach)
 
     // Let's copy beginning at the 1-slot offset in memory, but going
     // all the way as far as the length of all peripheral ROM in memory.
-    err = vm_segment_copy_buf(mach->memory, 
+    err = vm_segment_copy_buf(mach->main, 
                               objstore_apple2_peripheral_rom(),
                               APPLE2_PERIPHERAL_SLOT(1), 0, 
                               APPLE2_PERIPHERAL_SIZE);
@@ -123,7 +123,7 @@ apple2_mem_init_sys_rom(apple2 *mach)
     // The first two kilobytes of system rom are copied into memory
     // beginning at $C800 (which is just after all of the peripheral ROM
     // locations).
-    err = vm_segment_copy_buf(mach->memory, sysrom,
+    err = vm_segment_copy_buf(mach->main, sysrom,
                               0xC800, 0x800, 0x800);
     if (err != OK) {
         log_critical("Could not copy apple2 system rom");
diff --git a/src/mos6502.addr.c b/src/mos6502.addr.c
index 4cc9265..eeb369e 100644
--- a/src/mos6502.addr.c
+++ b/src/mos6502.addr.c
@@ -44,8 +44,8 @@ static int addr_modes[] = {
 #define ADDR_HILO(cpu) \
     vm_16bit addr; \
     vm_8bit hi, lo; \
-    lo = vm_segment_get(cpu->memory, cpu->PC + 1); \
-    hi = vm_segment_get(cpu->memory, cpu->PC + 2); \
+    lo = mos6502_get(cpu, cpu->PC + 1); \
+    hi = mos6502_get(cpu, cpu->PC + 2); \
     addr = (hi << 8) | lo
 
 /*
@@ -54,7 +54,7 @@ static int addr_modes[] = {
  */
 #define ADDR_LO(cpu) \
     vm_16bit addr; \
-    addr = vm_segment_get(cpu->memory, cpu->PC + 1)
+    addr = mos6502_get(cpu, cpu->PC + 1)
 
 /*
  * This will both define the `eff_addr` variable (which is the effective
@@ -100,7 +100,7 @@ DEFINE_ADDR(abs)
 {
     ADDR_HILO(cpu);
     EFF_ADDR(addr);
-    return vm_segment_get(cpu->memory, addr);
+    return mos6502_get(cpu, addr);
 }
 
 /*
@@ -115,7 +115,7 @@ DEFINE_ADDR(abx)
     MOS_CARRY_BIT();
     EFF_ADDR(addr + cpu->X + carry);
 
-    return vm_segment_get(cpu->memory, eff_addr);
+    return mos6502_get(cpu, eff_addr);
 }
 
 /*
@@ -128,7 +128,7 @@ DEFINE_ADDR(aby)
     MOS_CARRY_BIT();
     EFF_ADDR(addr + cpu->Y + carry);
 
-    return vm_segment_get(cpu->memory, eff_addr);
+    return mos6502_get(cpu, eff_addr);
 }
 
 /*
@@ -140,7 +140,7 @@ DEFINE_ADDR(aby)
 DEFINE_ADDR(imm)
 {
     EFF_ADDR(0);
-    return vm_segment_get(cpu->memory, cpu->PC + 1);
+    return mos6502_get(cpu, cpu->PC + 1);
 }
 
 /*
@@ -155,11 +155,11 @@ DEFINE_ADDR(ind)
 
     ADDR_HILO(cpu);
 
-    ind_lo = vm_segment_get(cpu->memory, addr);
-    ind_hi = vm_segment_get(cpu->memory, addr + 1);
+    ind_lo = mos6502_get(cpu, addr);
+    ind_hi = mos6502_get(cpu, addr + 1);
     EFF_ADDR((ind_hi << 8) | ind_lo);
 
-    return vm_segment_get(cpu->memory, eff_addr);
+    return mos6502_get(cpu, eff_addr);
 }
 
 /*
@@ -174,9 +174,9 @@ DEFINE_ADDR(idx)
     ADDR_LO(cpu);
     EFF_ADDR(addr + cpu->X);
 
-    return vm_segment_get(
-        cpu->memory, 
-        vm_segment_get(cpu->memory, eff_addr));
+    return mos6502_get(
+        cpu, 
+        mos6502_get(cpu, eff_addr));
 }
 
 /*
@@ -189,9 +189,9 @@ DEFINE_ADDR(idy)
 {
     ADDR_LO(cpu);
     MOS_CARRY_BIT();
-    EFF_ADDR(vm_segment_get(cpu->memory, addr) + cpu->Y + carry);
+    EFF_ADDR(mos6502_get(cpu, addr) + cpu->Y + carry);
 
-    return vm_segment_get(cpu->memory, eff_addr);
+    return mos6502_get(cpu, eff_addr);
 }
 
 /*
@@ -230,7 +230,7 @@ DEFINE_ADDR(zpg)
     ADDR_LO(cpu);
     EFF_ADDR(addr);
 
-    return vm_segment_get(cpu->memory, eff_addr);
+    return mos6502_get(cpu, eff_addr);
 }
 
 /*
@@ -242,7 +242,7 @@ DEFINE_ADDR(zpx)
     ADDR_LO(cpu);
     EFF_ADDR(addr + cpu->X);
 
-    return vm_segment_get(cpu->memory, eff_addr);
+    return mos6502_get(cpu, eff_addr);
 }
 
 /*
@@ -255,5 +255,5 @@ DEFINE_ADDR(zpy)
     ADDR_LO(cpu);
     EFF_ADDR(addr + cpu->Y);
 
-    return vm_segment_get(cpu->memory, eff_addr);
+    return mos6502_get(cpu, eff_addr);
 }
diff --git a/src/mos6502.arith.c b/src/mos6502.arith.c
index b33f17f..de23207 100644
--- a/src/mos6502.arith.c
+++ b/src/mos6502.arith.c
@@ -60,7 +60,7 @@ DEFINE_INST(cpy)
 DEFINE_INST(dec) 
 {
     if (cpu->last_addr) {
-        vm_segment_set(cpu->memory, cpu->last_addr, oper - 1);
+        mos6502_set(cpu, cpu->last_addr, oper - 1);
         mos6502_modify_status(cpu, MOS_NEGATIVE | MOS_ZERO, oper - 1);
     }
 }
@@ -91,7 +91,7 @@ DEFINE_INST(dey)
 DEFINE_INST(inc)
 {
     if (cpu->last_addr) {
-        vm_segment_set(cpu->memory, cpu->last_addr, oper + 1);
+        mos6502_set(cpu, cpu->last_addr, oper + 1);
         mos6502_modify_status(cpu, MOS_NEGATIVE | MOS_ZERO, oper + 1);
     }
 }
diff --git a/src/mos6502.bits.c b/src/mos6502.bits.c
index c73c59b..b60e788 100644
--- a/src/mos6502.bits.c
+++ b/src/mos6502.bits.c
@@ -39,7 +39,7 @@ DEFINE_INST(asl)
     oper <<= 1;
 
     if (cpu->last_addr) {
-        vm_segment_set(cpu->memory, cpu->last_addr, oper);
+        mos6502_set(cpu, cpu->last_addr, oper);
     } else {
         cpu->A = oper;
     }
@@ -98,7 +98,7 @@ DEFINE_INST(lsr)
     oper >>= 1;
 
     if (cpu->last_addr) {
-        vm_segment_set(cpu->memory, cpu->last_addr, oper);
+        mos6502_set(cpu, cpu->last_addr, oper);
     } else {
         cpu->A = oper;
     }
@@ -137,7 +137,7 @@ DEFINE_INST(rol)
     }
 
     if (cpu->last_addr) {
-        vm_segment_set(cpu->memory, cpu->last_addr, oper);
+        mos6502_set(cpu, cpu->last_addr, oper);
     } else {
         cpu->A = oper;
     }
@@ -164,7 +164,7 @@ DEFINE_INST(ror)
     }
 
     if (cpu->last_addr) {
-        vm_segment_set(cpu->memory, cpu->last_addr, oper);
+        mos6502_set(cpu, cpu->last_addr, oper);
     } else {
         cpu->A = oper;
     }
diff --git a/src/mos6502.c b/src/mos6502.c
index cd395e9..d5c84e6 100644
--- a/src/mos6502.c
+++ b/src/mos6502.c
@@ -145,7 +145,7 @@ static int cycles[] = {
  * used therein. All registers should be zeroed out.
  */
 mos6502 *
-mos6502_create()
+mos6502_create(vm_segment *rmem, vm_segment *wmem)
 {
     mos6502 *cpu;
    
@@ -155,7 +155,8 @@ mos6502_create()
         exit(1);
     }
 
-    cpu->memory = vm_segment_create(MOS6502_MEMSIZE);
+    cpu->rmem = rmem;
+    cpu->wmem = wmem;
 
     cpu->last_addr = 0;
     cpu->PC = 0;
@@ -174,7 +175,8 @@ mos6502_create()
 void
 mos6502_free(mos6502 *cpu)
 {
-    vm_segment_free(cpu->memory);
+    // Note we do not free rmem or wmem; we consider this to be the
+    // responsibility of the caller that passed us those values.
     free(cpu);
 }
 
@@ -192,11 +194,11 @@ mos6502_push_stack(mos6502 *cpu, vm_16bit addr)
 {
     // First we need to set the hi byte, by shifting the address right 8
     // positions and using the base offset of the S register.
-    vm_segment_set(cpu->memory, 0x0100 + cpu->S, addr & 0xff);
+    mos6502_set(cpu, 0x0100 + cpu->S, addr & 0xff);
 
     // Next we must record the lo byte, this time by using a bitmask to
     // capture just the low end of addr, but recording it in S + 1.
-    vm_segment_set(cpu->memory, 0x0100 + cpu->S + 1, addr >> 8);
+    mos6502_set(cpu, 0x0100 + cpu->S + 1, addr >> 8);
 
     // And finally we need to increment S by 2 (since we've used two
     // bytes in the stack).
@@ -216,7 +218,7 @@ mos6502_pop_stack(mos6502 *cpu)
     // We need to use a bitwise-or operation to combine the hi and lo
     // bytes we retrieve from the stack into the actual position we
     // would use for the PC register.
-    return vm_segment_get16(cpu->memory, 0x0100 + cpu->S);
+    return mos6502_get16(cpu, 0x0100 + cpu->S);
 }
 
 /*
@@ -341,7 +343,7 @@ mos6502_execute(mos6502 *cpu)
     mos6502_address_resolver resolver;
     mos6502_instruction_handler handler;
 
-    opcode = vm_segment_get(cpu->memory, cpu->PC);
+    opcode = mos6502_get(cpu, cpu->PC);
 
     // The disassembler knows how many bytes each operand requires
     // (maybe this code doesn't belong in the disassembler); let's use
@@ -425,7 +427,7 @@ mos6502_would_jump(int inst_code)
 void
 mos6502_flash_memory(mos6502 *cpu, vm_segment *segment)
 {
-    vm_segment_copy(cpu->memory, segment, 0, 0, cpu->memory->size - 1);
+    //vm_segment_copy(cpu, segment, 0, 0, cpu->size - 1);
 }
 
 /*
@@ -457,3 +459,26 @@ mos6502_get_address_resolver(vm_8bit opcode)
     return NULL;
 }
 
+inline vm_8bit
+mos6502_get(mos6502 *cpu, size_t addr)
+{
+    return vm_segment_get(cpu->rmem, addr);
+}
+
+inline vm_16bit
+mos6502_get16(mos6502 *cpu, size_t addr)
+{
+    return vm_segment_get16(cpu->rmem, addr);
+}
+
+inline void
+mos6502_set(mos6502 *cpu, size_t addr, vm_8bit value)
+{
+    vm_segment_set(cpu->wmem, addr, value);
+}
+
+inline void
+mos6502_set16(mos6502 *cpu, size_t addr, vm_16bit value)
+{
+    vm_segment_set16(cpu->wmem, addr, value);
+}
diff --git a/src/mos6502.dis.c b/src/mos6502.dis.c
index 61e401c..f1ee186 100644
--- a/src/mos6502.dis.c
+++ b/src/mos6502.dis.c
@@ -106,8 +106,8 @@ mos6502_dis_operand(mos6502 *cpu,
         case IMP:
             break;
         case IND:
-            ind_address = vm_segment_get(cpu->memory, value + 1) << 8;
-            ind_address |= vm_segment_get(cpu->memory, value);
+            ind_address = mos6502_get(cpu, value + 1) << 8;
+            ind_address |= mos6502_get(cpu, value);
             if (jump_table[ind_address]) {
                 mos6502_dis_label(stream, ind_address);
             } else {
@@ -218,7 +218,7 @@ mos6502_dis_opcode(mos6502 *cpu, FILE *stream, int address)
     int expected;
 
     // The next byte is assumed to be the opcode we work with.
-    opcode = vm_segment_get(cpu->memory, address);
+    opcode = mos6502_get(cpu, address);
 
     // And given that opcode, we need to see how many bytes large our
     // operand will be.
@@ -241,12 +241,12 @@ mos6502_dis_opcode(mos6502 *cpu, FILE *stream, int address)
             // Remember that the 6502 is little-endian, so the operand
             // needs to be retrieved with the LSB first and the MSB
             // second.
-            operand |= vm_segment_get(cpu->memory, address++);
-            operand |= vm_segment_get(cpu->memory, address++) << 8;
+            operand |= mos6502_get(cpu, address++);
+            operand |= mos6502_get(cpu, address++) << 8;
             break;
 
         case 1:
-            operand |= vm_segment_get(cpu->memory, address++);
+            operand |= mos6502_get(cpu, address++);
             break;
 
             // And, in any other case (e.g. 0), we are done; we don't
@@ -359,8 +359,8 @@ mos6502_dis_jump_label(mos6502 *cpu,
         // of the operand as a kind of double pointer, or just re-watch
         // Inception.
         case IND:
-            jump_loc = vm_segment_get(cpu->memory, operand + 1) << 8;
-            jump_loc |= vm_segment_get(cpu->memory, operand);
+            jump_loc = mos6502_get(cpu, operand + 1) << 8;
+            jump_loc |= mos6502_get(cpu, operand);
             break;
 
         // In relative address mode, the jump location will be a
diff --git a/src/mos6502.loadstor.c b/src/mos6502.loadstor.c
index 096af5b..7aab89d 100644
--- a/src/mos6502.loadstor.c
+++ b/src/mos6502.loadstor.c
@@ -75,7 +75,7 @@ DEFINE_INST(plp)
  */
 DEFINE_INST(sta)
 {
-    vm_segment_set(cpu->memory, cpu->last_addr, cpu->A);
+    mos6502_set(cpu, cpu->last_addr, cpu->A);
 }
 
 /*
@@ -83,7 +83,7 @@ DEFINE_INST(sta)
  */
 DEFINE_INST(stx)
 {
-    vm_segment_set(cpu->memory, cpu->last_addr, cpu->X);
+    mos6502_set(cpu, cpu->last_addr, cpu->X);
 }
 
 /*
@@ -91,7 +91,7 @@ DEFINE_INST(stx)
  */
 DEFINE_INST(sty)
 {
-    vm_segment_set(cpu->memory, cpu->last_addr, cpu->Y);
+    mos6502_set(cpu, cpu->last_addr, cpu->Y);
 }
 
 /*
diff --git a/tests/apple2.c b/tests/apple2.c
index 71a38ca..6d4a088 100644
--- a/tests/apple2.c
+++ b/tests/apple2.c
@@ -77,16 +77,16 @@ Test(apple2, boot)
 Test(apple2, press_key)
 {
     apple2_press_key(mach, 123);
-    cr_assert_eq(vm_segment_get(mach->memory, 0xC000), 123 | 0x80);
-    cr_assert_eq(vm_segment_get(mach->memory, 0xC010), 0x80);
+    cr_assert_eq(vm_segment_get(mach->main, 0xC000), 123 | 0x80);
+    cr_assert_eq(vm_segment_get(mach->main, 0xC010), 0x80);
 }
 
 Test(apple2, clear_strobe)
 {
     apple2_press_key(mach, 123);
-    cr_assert_eq(vm_segment_get(mach->memory, 0xC000), 123 | 0x80);
+    cr_assert_eq(vm_segment_get(mach->main, 0xC000), 123 | 0x80);
     apple2_clear_strobe(mach);
-    cr_assert_eq(vm_segment_get(mach->memory, 0xC000), 123);
+    cr_assert_eq(vm_segment_get(mach->main, 0xC000), 123);
 }
 
 /*
@@ -96,9 +96,9 @@ Test(apple2, clear_strobe)
 Test(apple2, release_key)
 {
     apple2_press_key(mach, 123);
-    cr_assert_eq(vm_segment_get(mach->memory, 0xC010), 0x80);
+    cr_assert_eq(vm_segment_get(mach->main, 0xC010), 0x80);
     apple2_release_key(mach);
-    cr_assert_eq(vm_segment_get(mach->memory, 0xC010), 0);
+    cr_assert_eq(vm_segment_get(mach->main, 0xC010), 0);
 }
 
 Test(apple2, set_color)
diff --git a/tests/apple2.mem.c b/tests/apple2.mem.c
index f99c445..08f5a51 100644
--- a/tests/apple2.mem.c
+++ b/tests/apple2.mem.c
@@ -29,8 +29,8 @@ Test(apple2_mem, map)
     size_t addr;
 
     for (addr = APPLE2_BANK_OFFSET; addr < MOS6502_MEMSIZE; addr++) {
-        cr_assert_eq(mach->memory->read_table[addr], apple2_mem_read_bank);
-        cr_assert_eq(mach->memory->write_table[addr], apple2_mem_write_bank);
+        cr_assert_eq(mach->main->read_table[addr], apple2_mem_read_bank);
+        cr_assert_eq(mach->main->write_table[addr], apple2_mem_write_bank);
     }
 }
 
@@ -44,15 +44,15 @@ Test(apple2_mem, read_bank)
     val = 123;
     vm_segment_set(mach->rom, 0x77, val);
     val = vm_segment_get(mach->rom, 0x77);
-    cr_assert_eq(vm_segment_get(mach->memory, 0xD077), val);
+    cr_assert_eq(vm_segment_get(mach->main, 0xD077), val);
 
     // In RAM1 bank mode, setting a value in memory should return thaty
     // value in memory... but, as a twist, also check that the value is
     // not set in ROM nor in RAM2.
     val = 222;
     apple2_set_bank_switch(mach, MEMORY_WRITE);
-    vm_segment_set(mach->memory, 0xD077, val);
-    cr_assert_eq(vm_segment_get(mach->memory, 0xD077), val);
+    vm_segment_set(mach->main, 0xD077, val);
+    cr_assert_eq(vm_segment_get(mach->main, 0xD077), val);
     cr_assert_neq(vm_segment_get(mach->rom, 0x77), val);
     cr_assert_neq(vm_segment_get(mach->ram2, 0x77), val);
 
@@ -62,7 +62,7 @@ Test(apple2_mem, read_bank)
     val = 111;
     apple2_set_bank_switch(mach, mach->bank_switch | MEMORY_RAM2);
     vm_segment_set(mach->ram2, 0x77, val);
-    cr_assert_eq(vm_segment_get(mach->memory, 0xD077), val);
+    cr_assert_eq(vm_segment_get(mach->main, 0xD077), val);
 }
 
 /*
@@ -82,17 +82,17 @@ Test(apple2_mem, write_bank)
     wrong = 222;
     apple2_set_bank_switch(mach, MEMORY_ROM);
     vm_segment_set(mach->rom, 0x77, right);
-    vm_segment_set(mach->memory, 0xD077, wrong);
+    vm_segment_set(mach->main, 0xD077, wrong);
     cr_assert_eq(vm_segment_get(mach->rom, 0x77), right);
-    cr_assert_eq(vm_segment_get(mach->memory, 0xD077), right);
+    cr_assert_eq(vm_segment_get(mach->main, 0xD077), right);
 
     // RAM1 is the main bank; it's all 64k RAM in one chunk.
     right = 111;
     wrong = 232;
     apple2_set_bank_switch(mach, MEMORY_WRITE);
-    vm_segment_set(mach->memory, 0xD078, right);
+    vm_segment_set(mach->main, 0xD078, right);
     vm_segment_set(mach->ram2, 0x78, wrong);
-    cr_assert_eq(vm_segment_get(mach->memory, 0xD078), right);
+    cr_assert_eq(vm_segment_get(mach->main, 0xD078), right);
     cr_assert_eq(vm_segment_get(mach->ram2, 0x78), wrong);
 
     // RAM2 is most of the 64k, except the first 4k of the last 12
@@ -101,7 +101,7 @@ Test(apple2_mem, write_bank)
     wrong = 132;
     apple2_set_bank_switch(mach, mach->bank_switch | MEMORY_RAM2);
     vm_segment_set(mach->ram2, 0x73, wrong);
-    vm_segment_set(mach->memory, 0xD073, right);
+    vm_segment_set(mach->main, 0xD073, right);
     cr_assert_eq(vm_segment_get(mach->ram2, 0x73), right);
 }
 
diff --git a/tests/mos6502.addr.c b/tests/mos6502.addr.c
index 5cf9d7d..8f84b7c 100644
--- a/tests/mos6502.addr.c
+++ b/tests/mos6502.addr.c
@@ -21,7 +21,7 @@ Test(mos6502_addr, addr_mode_acc)
 
 Test(mos6502_addr, addr_mode_abs)
 {
-    vm_segment_set(cpu->memory, 0x1234, 111);
+    mos6502_set(cpu, 0x1234, 111);
     SET_PC_BYTE(cpu, 1, 0x34);
     SET_PC_BYTE(cpu, 2, 0x12);
     cr_assert_eq(mos6502_resolve_abs(cpu), 111);
@@ -29,7 +29,7 @@ Test(mos6502_addr, addr_mode_abs)
 
 Test(mos6502_addr, addr_mode_abx_carry0)
 {
-    vm_segment_set(cpu->memory, 0x1234, 111);
+    mos6502_set(cpu, 0x1234, 111);
     SET_PC_BYTE(cpu, 1, 0x30);
     SET_PC_BYTE(cpu, 2, 0x12);
     cpu->X = 4;
@@ -38,7 +38,7 @@ Test(mos6502_addr, addr_mode_abx_carry0)
 
 Test(mos6502_addr, addr_mode_abx_carry1)
 {
-    vm_segment_set(cpu->memory, 0x1234, 111);
+    mos6502_set(cpu, 0x1234, 111);
     SET_PC_BYTE(cpu, 1, 0x30);
     SET_PC_BYTE(cpu, 2, 0x12);
     cpu->X = 3;
@@ -48,7 +48,7 @@ Test(mos6502_addr, addr_mode_abx_carry1)
 
 Test(mos6502_addr, addr_mode_aby_carry0)
 {
-    vm_segment_set(cpu->memory, 0x1234, 111);
+    mos6502_set(cpu, 0x1234, 111);
     SET_PC_BYTE(cpu, 1, 0x30);
     SET_PC_BYTE(cpu, 2, 0x12);
     cpu->Y = 4;
@@ -57,7 +57,7 @@ Test(mos6502_addr, addr_mode_aby_carry0)
 
 Test(mos6502_addr, addr_mode_aby_carry1)
 {
-    vm_segment_set(cpu->memory, 0x1234, 111);
+    mos6502_set(cpu, 0x1234, 111);
     SET_PC_BYTE(cpu, 1, 0x30);
     SET_PC_BYTE(cpu, 2, 0x12);
     cpu->Y = 3;
@@ -73,8 +73,8 @@ Test(mos6502_addr, addr_mode_imm)
 
 Test(mos6502_addr, addr_mode_idx)
 {
-    vm_segment_set(cpu->memory, 0x17, 0x23);
-    vm_segment_set(cpu->memory, 0x23, 123);
+    mos6502_set(cpu, 0x17, 0x23);
+    mos6502_set(cpu, 0x23, 123);
 
     SET_PC_BYTE(cpu, 1, 0x12);
     cpu->X = 5;
@@ -83,8 +83,8 @@ Test(mos6502_addr, addr_mode_idx)
 
 Test(mos6502_addr, addr_mode_idy)
 {
-    vm_segment_set(cpu->memory, 0x12, 0x23);
-    vm_segment_set(cpu->memory, 0x28, 123);
+    mos6502_set(cpu, 0x12, 0x23);
+    mos6502_set(cpu, 0x28, 123);
 
     SET_PC_BYTE(cpu, 1, 0x12);
     cpu->Y = 5;
@@ -93,9 +93,9 @@ Test(mos6502_addr, addr_mode_idy)
 
 Test(mos6502_addr, addr_mode_ind)
 {
-    vm_segment_set(cpu->memory, 0x1234, 0x45);
-    vm_segment_set(cpu->memory, 0x1235, 0x23);
-    vm_segment_set(cpu->memory, 0x2345, 123);
+    mos6502_set(cpu, 0x1234, 0x45);
+    mos6502_set(cpu, 0x1235, 0x23);
+    mos6502_set(cpu, 0x2345, 123);
 
     SET_PC_BYTE(cpu, 1, 0x34);
     SET_PC_BYTE(cpu, 2, 0x12);
@@ -120,14 +120,14 @@ Test(mos6502_addr, addr_mode_rel_negative)
 
 Test(mos6502_addr, addr_mode_zpg)
 {
-    vm_segment_set(cpu->memory, 0x0034, 222);
+    mos6502_set(cpu, 0x0034, 222);
     SET_PC_BYTE(cpu, 1, 0x34);
     cr_assert_eq(mos6502_resolve_zpg(cpu), 222);
 }
 
 Test(mos6502_addr, addr_mode_zpx)
 {
-    vm_segment_set(cpu->memory, 0x0034, 222);
+    mos6502_set(cpu, 0x0034, 222);
     SET_PC_BYTE(cpu, 1, 0x30);
     cpu->X = 4;
     cr_assert_eq(mos6502_resolve_zpx(cpu), 222);
@@ -135,7 +135,7 @@ Test(mos6502_addr, addr_mode_zpx)
 
 Test(mos6502_addr, addr_mode_zpy)
 {
-    vm_segment_set(cpu->memory, 0x0034, 222);
+    mos6502_set(cpu, 0x0034, 222);
     SET_PC_BYTE(cpu, 1, 0x2F);
     cpu->Y = 5;
     cr_assert_eq(mos6502_resolve_zpy(cpu), 222);
diff --git a/tests/mos6502.arith.c b/tests/mos6502.arith.c
index f1c3524..1f13e68 100644
--- a/tests/mos6502.arith.c
+++ b/tests/mos6502.arith.c
@@ -65,13 +65,13 @@ Test(mos6502_arith, dec)
     cr_assert_neq(cpu->A, 4);
 
     cpu->last_addr = 123;
-    vm_segment_set(cpu->memory, 123, 44);
+    mos6502_set(cpu, 123, 44);
 
     // Note _also_ that DEC expects the number to be decremented will be
     // passed in as the effective operand, although it doesn't
     // necessarily need for that to be so.
     mos6502_handle_dec(cpu, 44);
-    cr_assert_eq(vm_segment_get(cpu->memory, 123), 43);
+    cr_assert_eq(mos6502_get(cpu, 123), 43);
 }
 
 Test(mos6502_arith, dex)
@@ -92,7 +92,7 @@ Test(mos6502_arith, inc)
 {
     cpu->last_addr = 123;
     mos6502_handle_inc(cpu, 55);
-    cr_assert_eq(vm_segment_get(cpu->memory, 123), 56);
+    cr_assert_eq(mos6502_get(cpu, 123), 56);
 }
 
 Test(mos6502_arith, inx)
diff --git a/tests/mos6502.bits.c b/tests/mos6502.bits.c
index baa977c..1a883e9 100644
--- a/tests/mos6502.bits.c
+++ b/tests/mos6502.bits.c
@@ -24,7 +24,7 @@ Test(mos6502_bits, asl)
 
     cpu->last_addr = 123;
     mos6502_handle_asl(cpu, 22);
-    cr_assert_eq(vm_segment_get(cpu->memory, 123), 44);
+    cr_assert_eq(mos6502_get(cpu, 123), 44);
 }
 
 Test(mos6502_bits, bit)
@@ -75,7 +75,7 @@ Test(mos6502_bits, lsr)
 
     cpu->last_addr = 123;
     mos6502_handle_lsr(cpu, 22);
-    cr_assert_eq(vm_segment_get(cpu->memory, 123), 11);
+    cr_assert_eq(mos6502_get(cpu, 123), 11);
     cr_assert_eq(cpu->P & MOS_CARRY, MOS_CARRY);
 }
 
@@ -97,7 +97,7 @@ Test(mos6502_bits, rol)
 
     cpu->last_addr = 234;
     mos6502_handle_rol(cpu, 128);
-    cr_assert_eq(vm_segment_get(cpu->memory, 234), 1);
+    cr_assert_eq(mos6502_get(cpu, 234), 1);
 }
 
 Test(mos6502_bits, ror)
@@ -107,5 +107,5 @@ Test(mos6502_bits, ror)
 
     cpu->last_addr = 123;
     mos6502_handle_ror(cpu, 1);
-    cr_assert_eq(vm_segment_get(cpu->memory, 123), 128);
+    cr_assert_eq(mos6502_get(cpu, 123), 128);
 }
diff --git a/tests/mos6502.c b/tests/mos6502.c
index 6ee76cb..bc4d9b5 100644
--- a/tests/mos6502.c
+++ b/tests/mos6502.c
@@ -12,7 +12,8 @@ Test(mos6502, create)
 {
     cr_assert_neq(cpu, NULL);
 
-    cr_assert_eq(cpu->memory->size, MOS6502_MEMSIZE);
+    cr_assert_eq(cpu->rmem->size, MOS6502_MEMSIZE);
+    cr_assert_eq(cpu->wmem->size, MOS6502_MEMSIZE);
 
     cr_assert_eq(cpu->PC, 0);
     cr_assert_eq(cpu->A, 0);
@@ -25,8 +26,8 @@ Test(mos6502, create)
 Test(mos6502, push_stack)
 {
     mos6502_push_stack(cpu, 0x1234);
-    cr_assert_eq(vm_segment_get(cpu->memory, 0x0100), 0x34);
-    cr_assert_eq(vm_segment_get(cpu->memory, 0x0101), 0x12);
+    cr_assert_eq(mos6502_get(cpu, 0x0100), 0x34);
+    cr_assert_eq(mos6502_get(cpu, 0x0101), 0x12);
 }
 
 Test(mos6502, pop_stack)
@@ -97,8 +98,8 @@ Test(mos6502, get_instruction_handler)
 
 Test(mos6502, execute)
 {
-    vm_segment_set(cpu->memory, 11, 34);
-    vm_segment_set(cpu->memory, 10, 0x69);
+    mos6502_set(cpu, 11, 34);
+    mos6502_set(cpu, 10, 0x69);
     cpu->PC = 10;
     mos6502_execute(cpu);
     cr_assert_eq(cpu->A, 34);
@@ -134,19 +135,6 @@ Test(mos6502, would_jump)
     }
 }
 
-Test(mos6502, flash_memory)
-{
-    vm_segment *segment;
-
-    segment = vm_segment_create(MOS6502_MEMSIZE);
-    vm_segment_set(segment, 0, 123);
-    vm_segment_set(segment, 1, 124);
-    mos6502_flash_memory(cpu, segment);
-
-    cr_assert_eq(vm_segment_get(cpu->memory, 0), 123);
-    cr_assert_eq(vm_segment_get(cpu->memory, 1), 124);
-}
-
 Test(mos6502, get_address_resolver)
 {
     cr_assert_eq(mos6502_get_address_resolver(0x0A), mos6502_resolve_acc);
diff --git a/tests/mos6502.dis.c b/tests/mos6502.dis.c
index 7fd3c66..b06c7b5 100644
--- a/tests/mos6502.dis.c
+++ b/tests/mos6502.dis.c
@@ -17,7 +17,7 @@ static char buf[BUFSIZ];
  */
 static FILE *stream = NULL;
 static mos6502 *cpu = NULL;
-
+static vm_segment *mem = NULL;
 
 static void
 setup()
@@ -39,7 +39,8 @@ setup()
     // don't do that :D
     setvbuf(stream, buf, _IOFBF, 256);
 
-    cpu = mos6502_create();
+    mem = vm_segment_create(MOS6502_MEMSIZE);
+    cpu = mos6502_create(mem, mem);
 }
 
 static void
@@ -47,6 +48,7 @@ teardown()
 {
     fclose(stream);
     mos6502_free(cpu);
+    vm_segment_free(mem);
 }
 
 static void
@@ -81,8 +83,8 @@ Test(mos6502_dis, operand)
     mos6502_dis_operand(cpu, stream, 0, IMM, 0x12);
     assert_buf("#$12");
 
-    vm_segment_set(cpu->memory, 0x1234, 0x48);
-    vm_segment_set(cpu->memory, 0x1235, 0x34);
+    mos6502_set(cpu, 0x1234, 0x48);
+    mos6502_set(cpu, 0x1235, 0x34);
 
     // For JMPs and JSRs (and BRKs), this should be a label and not a
     // literal value. So we need to test both the literal and
@@ -210,8 +212,8 @@ Test(mos6502_dis, opcode)
 {
     int bytes;
 
-    vm_segment_set(cpu->memory, 0, 0x29);   // AND (imm)
-    vm_segment_set(cpu->memory, 1, 0x38);
+    mos6502_set(cpu, 0, 0x29);   // AND (imm)
+    mos6502_set(cpu, 1, 0x38);
 
     bytes = mos6502_dis_opcode(cpu, stream, 0);
     assert_buf("    AND     #$38	; pc=$0000 cy=02: 29 38\n");
@@ -220,12 +222,12 @@ Test(mos6502_dis, opcode)
 
 Test(mos6502_dis, scan)
 {
-    vm_segment_set(cpu->memory, 0, 0x29);   // AND (imm)
-    vm_segment_set(cpu->memory, 1, 0x38);
-    vm_segment_set(cpu->memory, 2, 0x88);   // DEY (imp)
-    vm_segment_set(cpu->memory, 3, 0x6C);   // JMP (ind)
-    vm_segment_set(cpu->memory, 4, 0x34);
-    vm_segment_set(cpu->memory, 5, 0x12);
+    mos6502_set(cpu, 0, 0x29);   // AND (imm)
+    mos6502_set(cpu, 1, 0x38);
+    mos6502_set(cpu, 2, 0x88);   // DEY (imp)
+    mos6502_set(cpu, 3, 0x6C);   // JMP (ind)
+    mos6502_set(cpu, 4, 0x34);
+    mos6502_set(cpu, 5, 0x12);
 
     mos6502_dis_scan(cpu, stream, 0, 6);
 
@@ -248,8 +250,8 @@ Test(mos6502_dis, jump_label)
 {
     cr_assert_eq(mos6502_dis_is_jump_label(123), false);
     
-    vm_segment_set(cpu->memory, 123, 5);
-    vm_segment_set(cpu->memory, 124, 0);
+    mos6502_set(cpu, 123, 5);
+    mos6502_set(cpu, 124, 0);
 
     mos6502_dis_jump_label(cpu, 123, 0, IND);
     cr_assert_eq(mos6502_dis_is_jump_label(5), true);
diff --git a/tests/mos6502.loadstor.c b/tests/mos6502.loadstor.c
index 7e99fc2..9dca110 100644
--- a/tests/mos6502.loadstor.c
+++ b/tests/mos6502.loadstor.c
@@ -29,8 +29,8 @@ Test(mos6502_loadstor, pha)
     cpu->A = 0x24;
     mos6502_handle_pha(cpu, 0);
 
-    cr_assert_eq(vm_segment_get(cpu->memory, 0x0100), 0x24);
-    cr_assert_eq(vm_segment_get(cpu->memory, 0x0101), 0x00);
+    cr_assert_eq(mos6502_get(cpu, 0x0100), 0x24);
+    cr_assert_eq(mos6502_get(cpu, 0x0101), 0x00);
 }
 
 Test(mos6502_loadstor, php)
@@ -38,8 +38,8 @@ Test(mos6502_loadstor, php)
     cpu->P = 0x43;
     mos6502_handle_php(cpu, 0);
 
-    cr_assert_eq(vm_segment_get(cpu->memory, 0x0100), 0x43);
-    cr_assert_eq(vm_segment_get(cpu->memory, 0x0101), 0x00);
+    cr_assert_eq(mos6502_get(cpu, 0x0100), 0x43);
+    cr_assert_eq(mos6502_get(cpu, 0x0101), 0x00);
 }
 
 Test(mos6502_loadstor, pla)
@@ -63,7 +63,7 @@ Test(mos6502_loadstor, sta)
     cpu->A = 123;
     cpu->last_addr = 555;
     mos6502_handle_sta(cpu, 0);
-    cr_assert_eq(vm_segment_get(cpu->memory, cpu->last_addr), cpu->A);
+    cr_assert_eq(mos6502_get(cpu, cpu->last_addr), cpu->A);
 }
 
 Test(mos6502_loadstor, stx)
@@ -71,7 +71,7 @@ Test(mos6502_loadstor, stx)
     cpu->X = 222;
     cpu->last_addr = 444;
     mos6502_handle_stx(cpu, 0);
-    cr_assert_eq(vm_segment_get(cpu->memory, cpu->last_addr), cpu->X);
+    cr_assert_eq(mos6502_get(cpu, cpu->last_addr), cpu->X);
 }
 
 Test(mos6502_loadstor, sty)
@@ -79,7 +79,7 @@ Test(mos6502_loadstor, sty)
     cpu->Y = 111;
     cpu->last_addr = 253;
     mos6502_handle_sty(cpu, 0);
-    cr_assert_eq(vm_segment_get(cpu->memory, cpu->last_addr), cpu->Y);
+    cr_assert_eq(mos6502_get(cpu, cpu->last_addr), cpu->Y);
 }
 
 Test(mos6502_loadstor, tax)