diff --git a/docs/architecture.md b/docs/architecture.md
index f8354a1..2eed403 100644
--- a/docs/architecture.md
+++ b/docs/architecture.md
@@ -101,4 +101,7 @@ registers, words (16-bit) for data, and 24-bit values for addresses
                                        than the second, and 0 if it isn't
 - `GTP (reg pair) (reg pair)` (0x38) - Sets `A` to 65535 if the first reg pair is greater
                                        than the second, and 0 if it isn't
+- `PUSHA (reg pair)` (0x39) - Pushes the given register pair to the stack
+- `POPA (reg pair)` (0x3A) - Pops a register pair from the stack and stores it in the
+                             given register pair
 - `HLT` (0xFF) - Stops execution
diff --git a/source/assembler/assembler.d b/source/assembler/assembler.d
index fb156eb..f22fd88 100644
--- a/source/assembler/assembler.d
+++ b/source/assembler/assembler.d
@@ -37,62 +37,64 @@ class Assembler {
 
 	this() {
 		// instructions
-		AddInstruction("nop",  Opcode.NOP,  []);
-		AddInstruction("set",  Opcode.SET,  [Param.Register, Param.Word]);
-		AddInstruction("xchg", Opcode.XCHG, [Param.Register, Param.Register]);
-		AddInstruction("wrb",  Opcode.WRB,  [Param.RegisterPair, Param.Register]);
-		AddInstruction("rdb",  Opcode.RDB,  [Param.RegisterPair]);
-		AddInstruction("wrw",  Opcode.WRW,  [Param.RegisterPair, Param.Register]);
-		AddInstruction("rdw",  Opcode.RDW,  [Param.RegisterPair]);
-		AddInstruction("add",  Opcode.ADD,  [Param.Register, Param.Register]);
-		AddInstruction("sub",  Opcode.SUB,  [Param.Register, Param.Register]);
-		AddInstruction("mul",  Opcode.MUL,  [Param.Register, Param.Register]);
-		AddInstruction("div",  Opcode.DIV,  [Param.Register, Param.Register]);
-		AddInstruction("mod",  Opcode.MOD,  [Param.Register, Param.Register]);
-		AddInstruction("inc",  Opcode.INC,  [Param.Register]);
-		AddInstruction("dec",  Opcode.DEC,  [Param.Register]);
-		AddInstruction("cmp",  Opcode.CMP,  [Param.Register, Param.Register]);
-		AddInstruction("not",  Opcode.NOT,  [Param.Register]);
-		AddInstruction("and",  Opcode.AND,  [Param.Register, Param.Register]);
-		AddInstruction("or",   Opcode.OR,   [Param.Register, Param.Register]);
-		AddInstruction("xor",  Opcode.XOR,  [Param.Register, Param.Register]);
-		AddInstruction("jnz",  Opcode.JNZ,  [Param.Addr]);
-		AddInstruction("jmp",  Opcode.JMP,  [Param.Addr]);
-		AddInstruction("out",  Opcode.OUT,  [Param.Register, Param.Register]);
-		AddInstruction("in",   Opcode.IN,   [Param.Register]);
-		AddInstruction("lda",  Opcode.LDA,  [Param.RegisterPair, Param.Addr]);
-		AddInstruction("incp", Opcode.INCP, [Param.RegisterPair]);
-		AddInstruction("decp", Opcode.DECP, [Param.RegisterPair]);
-		AddInstruction("setl", Opcode.SETL, [Param.Register]);
-		AddInstruction("cpl",  Opcode.CPL,  []);
-		AddInstruction("call", Opcode.CALL, [Param.Addr]);
-		AddInstruction("ret",  Opcode.RET,  []);
-		AddInstruction("int",  Opcode.INT,  [Param.Byte]);
-		AddInstruction("wra",  Opcode.WRA,  [Param.RegisterPair, Param.RegisterPair]);
-		AddInstruction("rda",  Opcode.RDA,  [Param.RegisterPair]);
-		AddInstruction("cpr",  Opcode.CPR,  [Param.Register, Param.Register]);
-		AddInstruction("cpp",  Opcode.CPP,  [Param.RegisterPair, Param.RegisterPair]);
-		AddInstruction("jmpb", Opcode.JMPB, [Param.Addr]);
-		AddInstruction("jnzb", Opcode.JNZB, [Param.Addr]);
-		AddInstruction("chk",  Opcode.CHK,  [Param.Register]);
-		AddInstruction("actv", Opcode.ACTV, [Param.Register]);
-		AddInstruction("addp", Opcode.ADDP, [Param.RegisterPair, Param.Register]);
-		AddInstruction("subp", Opcode.SUBP, [Param.RegisterPair, Param.Register]);
-		AddInstruction("diff", Opcode.DIFF, [Param.RegisterPair, Param.RegisterPair]);
-		AddInstruction("jz",   Opcode.JZ,   [Param.Addr]);
-		AddInstruction("jzb",  Opcode.JZB,  [Param.Addr]);
-		AddInstruction("rdbb", Opcode.RDBB, [Param.RegisterPair]);
-		AddInstruction("rdwb", Opcode.RDWB, [Param.RegisterPair]);
-		AddInstruction("rdab", Opcode.RDAB, [Param.RegisterPair]);
-		AddInstruction("wrbb", Opcode.WRBB, [Param.RegisterPair, Param.Register]);
-		AddInstruction("wrwb", Opcode.WRWB, [Param.RegisterPair, Param.Register]);
-		AddInstruction("wrab", Opcode.WRAB, [Param.RegisterPair, Param.RegisterPair]);
-		AddInstruction("lt",   Opcode.LT,   [Param.Register, Param.Register]);
-		AddInstruction("gt",   Opcode.GT,   [Param.Register, Param.Register]);
-		AddInstruction("cmpp", Opcode.CMPP, [Param.RegisterPair, Param.RegisterPair]);
-		AddInstruction("gtp",  Opcode.GTP, [Param.RegisterPair, Param.RegisterPair]);
-		AddInstruction("ltp",  Opcode.LTP, [Param.RegisterPair, Param.RegisterPair]);
-		AddInstruction("hlt",  Opcode.HLT,  []);
+		AddInstruction("nop",   Opcode.NOP,   []);
+		AddInstruction("set",   Opcode.SET,   [Param.Register, Param.Word]);
+		AddInstruction("xchg",  Opcode.XCHG,  [Param.Register, Param.Register]);
+		AddInstruction("wrb",   Opcode.WRB,   [Param.RegisterPair, Param.Register]);
+		AddInstruction("rdb",   Opcode.RDB,   [Param.RegisterPair]);
+		AddInstruction("wrw",   Opcode.WRW,   [Param.RegisterPair, Param.Register]);
+		AddInstruction("rdw",   Opcode.RDW,   [Param.RegisterPair]);
+		AddInstruction("add",   Opcode.ADD,   [Param.Register, Param.Register]);
+		AddInstruction("sub",   Opcode.SUB,   [Param.Register, Param.Register]);
+		AddInstruction("mul",   Opcode.MUL,   [Param.Register, Param.Register]);
+		AddInstruction("div",   Opcode.DIV,   [Param.Register, Param.Register]);
+		AddInstruction("mod",   Opcode.MOD,   [Param.Register, Param.Register]);
+		AddInstruction("inc",   Opcode.INC,   [Param.Register]);
+		AddInstruction("dec",   Opcode.DEC,   [Param.Register]);
+		AddInstruction("cmp",   Opcode.CMP,   [Param.Register, Param.Register]);
+		AddInstruction("not",   Opcode.NOT,   [Param.Register]);
+		AddInstruction("and",   Opcode.AND,   [Param.Register, Param.Register]);
+		AddInstruction("or",    Opcode.OR,    [Param.Register, Param.Register]);
+		AddInstruction("xor",   Opcode.XOR,   [Param.Register, Param.Register]);
+		AddInstruction("jnz",   Opcode.JNZ,   [Param.Addr]);
+		AddInstruction("jmp",   Opcode.JMP,   [Param.Addr]);
+		AddInstruction("out",   Opcode.OUT,   [Param.Register, Param.Register]);
+		AddInstruction("in",    Opcode.IN,    [Param.Register]);
+		AddInstruction("lda",   Opcode.LDA,   [Param.RegisterPair, Param.Addr]);
+		AddInstruction("incp",  Opcode.INCP,  [Param.RegisterPair]);
+		AddInstruction("decp",  Opcode.DECP,  [Param.RegisterPair]);
+		AddInstruction("setl",  Opcode.SETL,  [Param.Register]);
+		AddInstruction("cpl",   Opcode.CPL,   []);
+		AddInstruction("call",  Opcode.CALL,  [Param.Addr]);
+		AddInstruction("ret",   Opcode.RET,   []);
+		AddInstruction("int",   Opcode.INT,   [Param.Byte]);
+		AddInstruction("wra",   Opcode.WRA,   [Param.RegisterPair, Param.RegisterPair]);
+		AddInstruction("rda",   Opcode.RDA,   [Param.RegisterPair]);
+		AddInstruction("cpr",   Opcode.CPR,   [Param.Register, Param.Register]);
+		AddInstruction("cpp",   Opcode.CPP,   [Param.RegisterPair, Param.RegisterPair]);
+		AddInstruction("jmpb",  Opcode.JMPB,  [Param.Addr]);
+		AddInstruction("jnzb",  Opcode.JNZB,  [Param.Addr]);
+		AddInstruction("chk",   Opcode.CHK,   [Param.Register]);
+		AddInstruction("actv",  Opcode.ACTV,  [Param.Register]);
+		AddInstruction("addp",  Opcode.ADDP,  [Param.RegisterPair, Param.Register]);
+		AddInstruction("subp",  Opcode.SUBP,  [Param.RegisterPair, Param.Register]);
+		AddInstruction("diff",  Opcode.DIFF,  [Param.RegisterPair, Param.RegisterPair]);
+		AddInstruction("jz",    Opcode.JZ,    [Param.Addr]);
+		AddInstruction("jzb",   Opcode.JZB,   [Param.Addr]);
+		AddInstruction("rdbb",  Opcode.RDBB,  [Param.RegisterPair]);
+		AddInstruction("rdwb",  Opcode.RDWB,  [Param.RegisterPair]);
+		AddInstruction("rdab",  Opcode.RDAB,  [Param.RegisterPair]);
+		AddInstruction("wrbb",  Opcode.WRBB,  [Param.RegisterPair, Param.Register]);
+		AddInstruction("wrwb",  Opcode.WRWB,  [Param.RegisterPair, Param.Register]);
+		AddInstruction("wrab",  Opcode.WRAB,  [Param.RegisterPair, Param.RegisterPair]);
+		AddInstruction("lt",    Opcode.LT,    [Param.Register, Param.Register]);
+		AddInstruction("gt",    Opcode.GT,    [Param.Register, Param.Register]);
+		AddInstruction("cmpp",  Opcode.CMPP,  [Param.RegisterPair, Param.RegisterPair]);
+		AddInstruction("gtp",   Opcode.GTP,   [Param.RegisterPair, Param.RegisterPair]);
+		AddInstruction("ltp",   Opcode.LTP,   [Param.RegisterPair, Param.RegisterPair]);
+		AddInstruction("pusha", Opcode.PUSHA, [Param.RegisterPair]);
+		AddInstruction("popa",  Opcode.POPA,  [Param.RegisterPair]);
+		AddInstruction("hlt",   Opcode.HLT,  []);
 
 		// special
 		AddInstruction("db", Param.Byte);
diff --git a/source/computer.d b/source/computer.d
index cfb0444..fa45623 100644
--- a/source/computer.d
+++ b/source/computer.d
@@ -18,64 +18,66 @@ import yeti16.deviceBase;
 import yeti16.devices.disk;
 
 enum Opcode {
-	NOP  = 0x00,
-	SET  = 0x01,
-	XCHG = 0x02,
-	WRB  = 0x03,
-	RDB  = 0x04,
-	WRW  = 0x05,
-	RDW  = 0x06,
-	ADD  = 0x07,
-	SUB  = 0x08,
-	MUL  = 0x09,
-	DIV  = 0x0A,
-	MOD  = 0x0B,
-	INC  = 0x0C,
-	DEC  = 0x0D,
-	CMP  = 0x0E,
-	NOT  = 0x0F,
-	AND  = 0x10,
-	OR   = 0x11,
-	XOR  = 0x12,
-	JNZ  = 0x13,
-	JMP  = 0x14,
-	OUT  = 0x15,
-	IN   = 0x16,
-	LDA  = 0x17,
-	INCP = 0x18,
-	DECP = 0x19,
-	SETL = 0x1A,
-	CPL  = 0x1B,
-	CALL = 0x1C,
-	RET  = 0x1D,
-	INT  = 0x1E,
-	WRA  = 0x1F,
-	RDA  = 0x20,
-	CPR  = 0x21,
-	CPP  = 0x22,
-	JMPB = 0x23,
-	JNZB = 0x24,
-	CHK  = 0x25,
-	ACTV = 0x26,
-	ADDP = 0x27,
-	SUBP = 0x28,
-	DIFF = 0x29,
-	PUSH = 0x2A,
-	POP  = 0x2B,
-	JZ   = 0x2C,
-	JZB  = 0x2D,
-	RDBB = 0x2E,
-	RDWB = 0x2F,
-	RDAB = 0x30,
-	WRBB = 0x31,
-	WRWB = 0x32,
-	WRAB = 0x33,
-	LT   = 0x34,
-	GT   = 0x35,
-	CMPP = 0x36,
-	LTP  = 0x37,
-	GTP  = 0x38,
-	HLT  = 0xFF
+	NOP   = 0x00,
+	SET   = 0x01,
+	XCHG  = 0x02,
+	WRB   = 0x03,
+	RDB   = 0x04,
+	WRW   = 0x05,
+	RDW   = 0x06,
+	ADD   = 0x07,
+	SUB   = 0x08,
+	MUL   = 0x09,
+	DIV   = 0x0A,
+	MOD   = 0x0B,
+	INC   = 0x0C,
+	DEC   = 0x0D,
+	CMP   = 0x0E,
+	NOT   = 0x0F,
+	AND   = 0x10,
+	OR    = 0x11,
+	XOR   = 0x12,
+	JNZ   = 0x13,
+	JMP   = 0x14,
+	OUT   = 0x15,
+	IN    = 0x16,
+	LDA   = 0x17,
+	INCP  = 0x18,
+	DECP  = 0x19,
+	SETL  = 0x1A,
+	CPL   = 0x1B,
+	CALL  = 0x1C,
+	RET   = 0x1D,
+	INT   = 0x1E,
+	WRA   = 0x1F,
+	RDA   = 0x20,
+	CPR   = 0x21,
+	CPP   = 0x22,
+	JMPB  = 0x23,
+	JNZB  = 0x24,
+	CHK   = 0x25,
+	ACTV  = 0x26,
+	ADDP  = 0x27,
+	SUBP  = 0x28,
+	DIFF  = 0x29,
+	PUSH  = 0x2A,
+	POP   = 0x2B,
+	JZ    = 0x2C,
+	JZB   = 0x2D,
+	RDBB  = 0x2E,
+	RDWB  = 0x2F,
+	RDAB  = 0x30,
+	WRBB  = 0x31,
+	WRWB  = 0x32,
+	WRAB  = 0x33,
+	LT    = 0x34,
+	GT    = 0x35,
+	CMPP  = 0x36,
+	LTP   = 0x37,
+	GTP   = 0x38,
+	PUSHA = 0x39,
+	POPA  = 0x3A,
+	HLT   = 0xFF
 }
 
 enum Register {
@@ -740,6 +742,17 @@ class Computer {
 				a       = v1 > v2? 0xFFFF : 0;
 				break;
 			}
+			case Opcode.PUSHA: {
+				auto val = ReadRegPair(NextByte());
+				WriteAddr(sp, val);
+				sp += 3;
+				break;
+			}
+			case Opcode.POPA: {
+				sp -= 3;
+				WriteRegPair(NextByte(), ReadAddr(sp));
+				break;
+			}
 			case Opcode.HLT: {
 				halted = true;
 				break;