diff --git a/cpu.c b/cpu.c
index c0e3877..acb4efb 100644
--- a/cpu.c
+++ b/cpu.c
@@ -559,21 +559,21 @@ sei(uint8_t arg)
 }
 
 static void
-sta(uint8_t arg)
+sta(uint16_t mem)
 {
-/* TODO: complete this */
+	memwrite(mem, regs.a);
 }
 
 static void
-stx(uint8_t arg)
+stx(uint16_t mem)
 {
-/* TODO: complete this */
+	memwrite(mem, regs.x);
 }
 
 static void
-sty(uint8_t arg)
+sty(uint16_t mem)
 {
-/* TODO: complete this */
+	memwrite(mem, regs.y);
 }
 
 static void
@@ -1219,59 +1219,59 @@ interpret(void)
 			cycles += 2;
 			break;
 		case 0x85:
-			sta(opcode_arg(AM_ZP));
+			sta(opcode_mem(AM_ZP));
 			cycles += 4;
 			break;
 		case 0x95:
-			sta(opcode_arg(AM_ZP_X));
+			sta(opcode_mem(AM_ZP_X));
 			cycles += 5;
 			break;
 		case 0x8d:
-			sta(opcode_arg(AM_ABS));
+			sta(opcode_mem(AM_ABS));
 			cycles += 5;
 			break;
 		case 0x9d:
-			sta(opcode_arg(AM_ABS_X));
+			sta(opcode_mem(AM_ABS_X));
 			cycles += 6;
 			break;
 		case 0x99:
-			sta(opcode_arg(AM_ABS_Y));
+			sta(opcode_mem(AM_ABS_Y));
 			cycles += 6;
 			break;
 		case 0x92:
-			sta(opcode_arg(AM_IND));
+			sta(opcode_mem(AM_IND));
 			cycles += 6;
 			break;
 		case 0x81:
-			sta(opcode_arg(AM_IND_X));
+			sta(opcode_mem(AM_IND_X));
 			cycles += 7;
 			break;
 		case 0x91:
-			sta(opcode_arg(AM_IND_Y));
+			sta(opcode_mem(AM_IND_Y));
 			cycles += 7;
 			break;
 		case 0x86:
-			stx(opcode_arg(AM_ZP));
+			stx(opcode_mem(AM_ZP));
 			cycles += 4;
 			break;
 		case 0x96:
-			stx(opcode_arg(AM_ZP_Y));
+			stx(opcode_mem(AM_ZP_Y));
 			cycles += 5;
 			break;
 		case 0x8e:
-			stx(opcode_arg(AM_ABS));
+			stx(opcode_mem(AM_ABS));
 			cycles += 5;
 			break;
 		case 0x84:
-			sty(opcode_arg(AM_ZP));
+			sty(opcode_mem(AM_ZP));
 			cycles += 4;
 			break;
 		case 0x94:
-			sty(opcode_arg(AM_ZP_X));
+			sty(opcode_mem(AM_ZP_X));
 			cycles += 5;
 			break;
 		case 0x8c:
-			sty(opcode_arg(AM_ABS));
+			sty(opcode_mem(AM_ABS));
 			cycles += 5;
 			break;
 		case 0xaa: