diff --git a/src/gamegear.c b/src/gamegear.c
index 8aa14d1..e08cc72 100644
--- a/src/gamegear.c
+++ b/src/gamegear.c
@@ -141,10 +141,10 @@ static bool simulate_frame(GameGear *gg)
     bool except;
 
     for (line = 0; line < VDP_LINES_PER_FRAME; line++) {
-        vdp_simulate_line(&gg->vdp);
         except = z80_do_cycles(&gg->cpu, CYCLES_PER_LINE);
         if (except)
             return true;
+        vdp_simulate_line(&gg->vdp);
     }
     return false;
 }
diff --git a/src/z80.c b/src/z80.c
index 3bfc711..0cbbe24 100644
--- a/src/z80.c
+++ b/src/z80.c
@@ -178,7 +178,7 @@ static inline uint8_t* extract_reg(Z80 *z80, uint8_t opcode)
 }
 
 /*
-    Extract a register pair from the given opcode and return a pointer to it.
+    Extract a ss/dd register pair from the given opcode and return a pointer.
 */
 static inline uint16_t* extract_pair(Z80 *z80, uint8_t opcode)
 {
@@ -192,6 +192,20 @@ static inline uint16_t* extract_pair(Z80 *z80, uint8_t opcode)
 }
 
 /*
+    Extract a qq register pair from the given opcode and return a pointer.
+*/
+static inline uint16_t* extract_pair_qq(Z80 *z80, uint8_t opcode)
+{
+    switch (opcode & 0x30) {
+        case 0x00: return &z80->regs.bc;
+        case 0x10: return &z80->regs.de;
+        case 0x20: return &z80->regs.hl;
+        case 0x30: return &z80->regs.af;
+    }
+    FATAL("invalid call: extract_pair_qq(z80, 0x%02X)", opcode)
+}
+
+/*
     Extract a condition from the given opcode.
 */
 static inline bool extract_cond(const Z80 *z80, uint8_t opcode)
diff --git a/src/z80_flags.inc.c b/src/z80_flags.inc.c
index d64cf35..ae9d8a7 100644
--- a/src/z80_flags.inc.c
+++ b/src/z80_flags.inc.c
@@ -157,6 +157,33 @@ static inline void set_flags_neg(Z80 *z80)
         HALF(0, -, val), F5(res), ZERO(res), SIGN(res), 0xFF);
 }
 
+/*
+    Set the flags for a LDI/LDIR/LDD/LDDR instruction.
+*/
+static inline void set_flags_blockxfer(Z80 *z80, uint8_t val)
+{
+    bool pv = z80->regs.bc != 0;
+    uint8_t res = val + z80->regs.a;
+    set_flags(z80, 0, 0, pv, res & 0x08, 0, res & 0x02, 0, 0, 0x3E);
+}
+
+/*
+    Set the flags for an IN instruction.
+*/
+static inline void set_flags_in(Z80 *z80, uint8_t val)
+{
+    set_flags(z80, 0, 0, PARITY(val), F3(val), 0, F5(val), ZERO(val),
+        SIGN(val), 0xFE);
+}
+
+/*
+    Set the flags for an INI/INIR/IND/INDR/OUTI/OTIR/OUTD/OTDR instruction.
+*/
+static inline void set_flags_blockio(Z80 *z80)
+{
+    set_flags_dec(z80, z80->regs.b);
+}
+
 #undef POS
 #undef NEG
 #undef CARRY
diff --git a/src/z80_ops.inc.c b/src/z80_ops.inc.c
index 198a3b5..23c838c 100644
--- a/src/z80_ops.inc.c
+++ b/src/z80_ops.inc.c
@@ -311,7 +311,7 @@ static uint8_t z80_inst_ld_inn_dd(Z80 *z80, uint8_t opcode)
     uint16_t addr = mmu_read_double(z80->mmu, ++z80->regs.pc);
     mmu_write_double(z80->mmu, addr, *extract_pair(z80, opcode));
     z80->regs.pc += 2;
-    return 16;
+    return 20;
 }
 
 /*
@@ -357,7 +357,7 @@ static uint8_t z80_inst_ld_sp_ixy(Z80 *z80, uint8_t opcode)
 */
 static uint8_t z80_inst_push_qq(Z80 *z80, uint8_t opcode)
 {
-    stack_push(z80, *extract_pair(z80, opcode));
+    stack_push(z80, *extract_pair_qq(z80, opcode));
     z80->regs.pc++;
     return 11;
 }
@@ -380,7 +380,7 @@ static uint8_t z80_inst_push_ixy(Z80 *z80, uint8_t opcode)
 */
 static uint8_t z80_inst_pop_qq(Z80 *z80, uint8_t opcode)
 {
-    *extract_pair(z80, opcode) = stack_pop(z80);
+    *extract_pair_qq(z80, opcode) = stack_pop(z80);
     z80->regs.pc++;
     return 10;
 }
@@ -479,14 +479,14 @@ static uint8_t z80_inst_ex_sp_ixy(Z80 *z80, uint8_t opcode)
 static uint8_t z80_inst_ldi(Z80 *z80, uint8_t opcode)
 {
     (void) opcode;
-    uint16_t value = mmu_read_double(z80->mmu, z80->regs.hl);
-    mmu_write_double(z80->mmu, z80->regs.de, value);
+    uint8_t value = mmu_read_byte(z80->mmu, z80->regs.hl);
+    mmu_write_byte(z80->mmu, z80->regs.de, value);
 
     z80->regs.hl++;
     z80->regs.de++;
     z80->regs.bc--;
 
-    set_flags(z80, 0, 0, z80->regs.bc == 0, 0, 0, 0, 0, 0, 0x16);
+    set_flags_blockxfer(z80, value);
     z80->regs.pc++;
     return 16;
 }
@@ -511,14 +511,14 @@ static uint8_t z80_inst_ldir(Z80 *z80, uint8_t opcode)
 static uint8_t z80_inst_ldd(Z80 *z80, uint8_t opcode)
 {
     (void) opcode;
-    uint16_t value = mmu_read_double(z80->mmu, z80->regs.hl);
-    mmu_write_double(z80->mmu, z80->regs.de, value);
+    uint8_t value = mmu_read_byte(z80->mmu, z80->regs.hl);
+    mmu_write_byte(z80->mmu, z80->regs.de, value);
 
     z80->regs.hl--;
     z80->regs.de--;
     z80->regs.bc--;
 
-    set_flags(z80, 0, 0, z80->regs.bc == 0, 0, 0, 0, 0, 0, 0x16);
+    set_flags_blockxfer(z80, value);
     z80->regs.pc++;
     return 16;
 }
@@ -1737,7 +1737,7 @@ static uint8_t z80_inst_bit_b_hl(Z80 *z80, uint8_t opcode)
 
     set_flags_bit(z80, val, bit);
     z80->regs.pc++;
-    return 8;
+    return 12;
 }
 
 /*
@@ -1752,7 +1752,7 @@ static uint8_t z80_inst_bit_b_ixy(Z80 *z80, uint8_t opcode)
 
     set_flags_bit(z80, val, bit);
     z80->regs.pc++;
-    return 8;
+    return 20;
 }
 
 // TODO: SET b, r
@@ -1775,7 +1775,7 @@ static uint8_t z80_inst_res_b_hl(Z80 *z80, uint8_t opcode)
     val &= ~(1 << bit);
     mmu_write_byte(z80->mmu, z80->regs.hl, val);
     z80->regs.pc++;
-    return 8;
+    return 15;
 }
 
 // TODO: RES b, (IXY+d)
@@ -1981,12 +1981,10 @@ static uint8_t z80_inst_in_a_n(Z80 *z80, uint8_t opcode)
 static uint8_t z80_inst_in_r_c(Z80 *z80, uint8_t opcode)
 {
     uint8_t data = read_port(z80, z80->regs.c);
-    bool parity = !(__builtin_popcount(data) % 2);
-
     if (opcode != 0x70)
         *extract_reg(z80, opcode) = data;
-    set_flags(z80, 0, 0, parity, !!(data & 0x08), 0, !!(data & 0x20),
-        data == 0, !!(data & 0x80), 0xFE);
+
+    set_flags_in(z80, data);
     z80->regs.pc++;
     return 12;
 }
@@ -1998,15 +1996,11 @@ static uint8_t z80_inst_in_r_c(Z80 *z80, uint8_t opcode)
 static uint8_t z80_inst_ini(Z80 *z80, uint8_t opcode)
 {
     (void) opcode;
-    uint8_t data = read_port(z80, z80->regs.c), *b = &z80->regs.b;
-    bool h = !!(((*b & 0x0F) - 1) & 0x10);
+    mmu_write_byte(z80->mmu, z80->regs.hl, read_port(z80, z80->regs.c));
+    set_flags_blockio(z80);
 
-    mmu_write_byte(z80->mmu, z80->regs.hl, data);
     z80->regs.hl++;
-    (*b)--;
-
-    set_flags(z80, 0, 1, *b == 0x7F, !!(*b & 0x08), h, !!(*b & 0x20),
-        *b == 0, !!(*b & 0x80), 0xFE);
+    z80->regs.b--;
     z80->regs.pc++;
     return 16;
 }
@@ -2031,15 +2025,11 @@ static uint8_t z80_inst_inir(Z80 *z80, uint8_t opcode)
 static uint8_t z80_inst_ind(Z80 *z80, uint8_t opcode)
 {
     (void) opcode;
-    uint8_t data = read_port(z80, z80->regs.c), *b = &z80->regs.b;
-    bool h = !!(((*b & 0x0F) - 1) & 0x10);
+    mmu_write_byte(z80->mmu, z80->regs.hl, read_port(z80, z80->regs.c));
+    set_flags_blockio(z80);
 
-    mmu_write_byte(z80->mmu, z80->regs.hl, data);
     z80->regs.hl--;
-    (*b)--;
-
-    set_flags(z80, 0, 1, *b == 0x7F, !!(*b & 0x08), h, !!(*b & 0x20),
-        *b == 0, !!(*b & 0x80), 0xFE);
+    z80->regs.b--;
     z80->regs.pc++;
     return 16;
 }
@@ -2090,15 +2080,11 @@ static uint8_t z80_inst_out_c_r(Z80 *z80, uint8_t opcode)
 static uint8_t z80_inst_outi(Z80 *z80, uint8_t opcode)
 {
     (void) opcode;
-    uint8_t *b = &z80->regs.b;
-    bool h = !!(((*b & 0x0F) - 1) & 0x10);
-
     write_port(z80, z80->regs.c, mmu_read_byte(z80->mmu, z80->regs.hl));
-    z80->regs.hl++;
-    (*b)--;
+    set_flags_blockio(z80);
 
-    set_flags(z80, 0, 1, *b == 0x7F, !!(*b & 0x08), h, !!(*b & 0x20),
-        *b == 0, !!(*b & 0x80), 0xFE);
+    z80->regs.hl++;
+    z80->regs.b--;
     z80->regs.pc++;
     return 16;
 }
@@ -2123,15 +2109,11 @@ static uint8_t z80_inst_otir(Z80 *z80, uint8_t opcode)
 static uint8_t z80_inst_outd(Z80 *z80, uint8_t opcode)
 {
     (void) opcode;
-    uint8_t *b = &z80->regs.b;
-    bool h = !!(((*b & 0x0F) - 1) & 0x10);
-
     write_port(z80, z80->regs.c, mmu_read_byte(z80->mmu, z80->regs.hl));
-    z80->regs.hl--;
-    (*b)--;
+    set_flags_blockio(z80);
 
-    set_flags(z80, 0, 1, *b == 0x7F, !!(*b & 0x08), h, !!(*b & 0x20),
-        *b == 0, !!(*b & 0x80), 0xFE);
+    z80->regs.hl--;
+    z80->regs.b--;
     z80->regs.pc++;
     return 16;
 }