diff --git a/src/cpu/arm/block_data_transfer.zig b/src/cpu/arm/block_data_transfer.zig
index f72e9b0..892eeeb 100644
--- a/src/cpu/arm/block_data_transfer.zig
+++ b/src/cpu/arm/block_data_transfer.zig
@@ -48,17 +48,17 @@ pub fn blockDataTransfer(comptime P: bool, comptime U: bool, comptime S: bool, c
             var address = start;
 
             if (rlist == 0) {
-                var pc_addr = cpu.r[rn];
+                var und_addr = cpu.r[rn];
                 if (U) {
-                    pc_addr += if (P) 4 else 0;
+                    und_addr += if (P) 4 else 0;
                 } else {
-                    pc_addr -= 0x40 - if (!P) 4 else 0;
+                    und_addr -= 0x40 - if (!P) 4 else 0;
                 }
 
                 if (L) {
-                    cpu.r[15] = bus.read32(pc_addr);
+                    cpu.r[15] = bus.read32(und_addr & 0xFFFF_FFFC);
                 } else {
-                    bus.write32(pc_addr, cpu.r[15] + 8);
+                    bus.write32(und_addr & 0xFFFF_FFFC, cpu.r[15] + 8);
                 }
 
                 cpu.r[rn] = if (U) cpu.r[rn] + 0x40 else cpu.r[rn] - 0x40;
@@ -85,9 +85,9 @@ pub fn blockDataTransfer(comptime P: bool, comptime U: bool, comptime S: bool, c
             if (L) {
                 if (S and !r15_present) {
                     // Always Transfer User mode Registers
-                    cpu.setUserModeRegister(i, bus.read32(address));
+                    cpu.setUserModeRegister(i, bus.read32(address & 0xFFFF_FFFC));
                 } else {
-                    const value = bus.read32(address);
+                    const value = bus.read32(address & 0xFFFF_FFFC);
                     cpu.r[i] = if (i == 0xF) value & 0xFFFF_FFFC else value;
                     if (S and i == 0xF) cpu.setCpsr(cpu.spsr.raw);
                 }
@@ -96,9 +96,9 @@ pub fn blockDataTransfer(comptime P: bool, comptime U: bool, comptime S: bool, c
                     // Always Transfer User mode Registers
                     // This happens regardless if r15 is in the list
                     const value = cpu.getUserModeRegister(i);
-                    bus.write32(address, value + if (i == 0xF) 8 else @as(u32, 0)); // PC is already 4 ahead to make 12
+                    bus.write32(address & 0xFFFF_FFFC, value + if (i == 0xF) 8 else @as(u32, 0)); // PC is already 4 ahead to make 12
                 } else {
-                    bus.write32(address, cpu.r[i] + if (i == 0xF) 8 else @as(u32, 0));
+                    bus.write32(address & 0xFFFF_FFFC, cpu.r[i] + if (i == 0xF) 8 else @as(u32, 0));
                 }
             }
         }
diff --git a/src/cpu/thumb/block_data_transfer.zig b/src/cpu/thumb/block_data_transfer.zig
index 098d344..975623d 100644
--- a/src/cpu/thumb/block_data_transfer.zig
+++ b/src/cpu/thumb/block_data_transfer.zig
@@ -5,44 +5,42 @@ const InstrFn = @import("../../cpu.zig").ThumbInstrFn;
 pub fn format14(comptime L: bool, comptime R: bool) InstrFn {
     return struct {
         fn inner(cpu: *Arm7tdmi, bus: *Bus, opcode: u16) void {
-            var address: u32 = undefined;
+            const count = countRlist(opcode);
+            const start = cpu.r[13] - if (!L) 4 * (@boolToInt(R) + count) else 0;
+
+            var end = cpu.r[13];
             if (L) {
-                // POP
-                address = cpu.r[13];
-
-                var i: u4 = 0;
-                while (i < 8) : (i += 1) {
-                    if ((opcode >> i) & 1 == 1) {
-                        cpu.r[i] = bus.read32(address);
-                        address += 4;
-                    }
-                }
-
-                if (R) {
-                    const value = bus.read32(address);
-                    cpu.r[15] = value & 0xFFFF_FFFE;
-                    address += 4;
-                }
+                end += 4 * (@boolToInt(R) + count);
             } else {
-                address = cpu.r[13] - 4;
+                end -= 4;
+            }
 
-                if (R) {
-                    bus.write32(address, cpu.r[14]);
-                    address -= 4;
-                }
+            var address = start;
 
-                var i: u4 = 8;
-                while (i > 0) : (i -= 1) {
-                    const j = i - 1;
-
-                    if ((opcode >> j) & 1 == 1) {
-                        bus.write32(address, cpu.r[j]);
-                        address -= 4;
+            var i: u4 = 0;
+            while (i < 8) : (i += 1) {
+                if (opcode >> i & 1 == 1) {
+                    if (L) {
+                        cpu.r[i] = bus.read32(address & 0xFFFF_FFFC);
+                    } else {
+                        bus.write32(address & 0xFFFF_FFFC, cpu.r[i]);
                     }
+
+                    address += 4;
                 }
             }
 
-            cpu.r[13] = address + if (!L) 4 else 0;
+            if (R) {
+                if (L) {
+                    const value = bus.read32(address & 0xFFFF_FFFC);
+                    cpu.r[15] = value & 0xFFFF_FFFE;
+                } else {
+                    bus.write32(address & 0xFFFF_FFFC, cpu.r[14]);
+                }
+                address += 4;
+            }
+
+            cpu.r[13] = if (L) end else cpu.r[13] - 4 * (@boolToInt(R) + count);
         }
     }.inner;
 }
@@ -54,7 +52,7 @@ pub fn format15(comptime L: bool, comptime rb: u3) InstrFn {
             const end_address = cpu.r[rb] + 4 * countRlist(opcode);
 
             if (opcode & 0xFF == 0) {
-                if (L) cpu.r[15] = bus.read32(address) else bus.write32(address, cpu.r[15] + 4);
+                if (L) cpu.r[15] = bus.read32(address & 0xFFFF_FFFC) else bus.write32(address & 0xFFFF_FFFC, cpu.r[15] + 4);
                 cpu.r[rb] += 0x40;
                 return;
             }
@@ -65,9 +63,9 @@ pub fn format15(comptime L: bool, comptime rb: u3) InstrFn {
             while (i < 8) : (i += 1) {
                 if (opcode >> i & 1 == 1) {
                     if (L) {
-                        cpu.r[i] = bus.read32(address);
+                        cpu.r[i] = bus.read32(address & 0xFFFF_FFFC);
                     } else {
-                        bus.write32(address, cpu.r[i]);
+                        bus.write32(address & 0xFFFF_FFFC, cpu.r[i]);
                     }
 
                     if (!L and first_write) {