diff --git a/mach/pdp/as/mach0.c b/mach/pdp/as/mach0.c
new file mode 100644
index 000000000..cd5836ce0
--- /dev/null
+++ b/mach/pdp/as/mach0.c
@@ -0,0 +1,15 @@
+#define RCSID0 "$Header$"
+
+/*
+ * PDP 11 machine dependent options
+ */
+
+#define THREE_PASS
+#define WORDS_REVERSED
+#define LISTING
+#define RELOCATION
+
+#undef ALIGNWORD
+#define ALIGNWORD 2
+#undef ALIGNSECT
+#define ALIGNSECT 2
diff --git a/mach/pdp/as/mach1.c b/mach/pdp/as/mach1.c
new file mode 100644
index 000000000..73aeed329
--- /dev/null
+++ b/mach/pdp/as/mach1.c
@@ -0,0 +1,35 @@
+#define RCSID1 "$Header$"
+
+#
+/*
+ * PDP 11 Machine dependent C declarations
+ */
+
+/* Addressing modes */
+#define RMODE		00
+#define AIMODE		020
+#define ADMODE		040
+#define INDMODE		060
+#define RDEFMODE	010
+#define AIDEFMODE	030
+#define ADDEFMODE	050
+#define INDDEFMODE	070
+
+#define OPLDF 0172400
+#define OPSTF 0174000
+#define OPSOB 077000
+#define OPBRA 0400
+
+#define low3(z)	(((short) z) & 07)
+#define low6(z)	(((short) z) & 077)
+#define low7(z) (((short) z) & 0177)
+
+#define fit3(z)	(low3(z) == (z))
+#define fit6(z)	(low6(z) == (z))
+#define fit8(z)	(lowb(z) == (z))
+
+extern expr_t exp_1, exp_2;
+extern int rel_1, rel_2;
+extern int im1flag INIT(0);
+extern int im2flag INIT(0);
+extern valu_t adjust();
diff --git a/mach/pdp/as/mach2.c b/mach/pdp/as/mach2.c
new file mode 100644
index 000000000..72fcbe951
--- /dev/null
+++ b/mach/pdp/as/mach2.c
@@ -0,0 +1,36 @@
+#define RCSID2 "$Header$"
+
+/*
+* PDP 11 machine dependent yacc declarations
+*/
+%token <y_word> REG
+%token <y_word> FREG
+%token <y_word> FRSP
+%token <y_word> JMP
+%token <y_word> OP_SO
+%token <y_word> OP_DO
+%token <y_word> OP_R_SO
+%token <y_word> BR
+%token <y_word> EJMP
+%token <y_word> JSR
+%token <y_word> RTS
+%token <y_word> MARK
+%token <y_word> SOB
+%token <y_word> SPL
+%token <y_word> TRAP
+%token <y_word> OP_NO
+%token <y_word> OP_SO_R
+%token <y_word> MFP
+%token <y_word> FOP_FSO_FR
+%token <y_word> FOP_NO
+%token <y_word> FOP_FSO
+%token <y_word> FOP_SO
+%token <y_word> MOVF
+%token <y_word> FOP_SO_FR
+%token <y_word> FOP_FR_SO
+%token <y_word> FOP_FR_FSO
+%token <y_word> CLEARCC
+%token <y_word> SETCC
+
+%type <y_word> opr1, opr2, op2, fopr2, fopr1, ari, ainc, adec
+%type <y_word> fop2, clcc, secc, fregister
diff --git a/mach/pdp/as/mach3.c b/mach/pdp/as/mach3.c
new file mode 100644
index 000000000..124787142
--- /dev/null
+++ b/mach/pdp/as/mach3.c
@@ -0,0 +1,152 @@
+#define RCSID3 "$Header$"
+
+/*,
+ * PDP 11 keywords,
+ */
+0,		REG,		00,		"r0",
+0,		REG,		01,		"r1",
+0,		REG,		02,		"r2",
+0,		REG,		03,		"r3",
+0,		REG,		04,		"r4",
+0,		REG,		05,		"r5",
+0,		REG,		06,		"r6",
+0,		REG,		06,		"sp",
+0,		REG,		07,		"r7",
+0,		REG,		07,		"pc",
+0,		FREG,		00,		"fr0",
+0,		FREG,		01,		"fr1",
+0,		FREG,		02,		"fr2",
+0,		FREG,		03,		"fr3",
+0,		FRSP,		04,		"fr4",
+0,		FRSP,		05,		"fr5",
+0,		OP_SO,		05000,		"clr",
+0,		OP_SO,		0105000,	"clrb",
+0,		OP_SO,		05100,		"com",
+0,		OP_SO,		0105100,	"comb",
+0,		OP_SO,		005200,		"inc",
+0,		OP_SO,		0105200,	"incb",
+0,		OP_SO,		005300,		"dec",
+0,		OP_SO,		0105300,	"decb",
+0,		OP_SO,		005400,		"neg",
+0,		OP_SO,		0105400,	"negb",
+0,		OP_SO,		005700,		"tst",
+0,		OP_SO,		0105700,	"tstb",
+0,		OP_SO,		006200,		"asr",
+0,		OP_SO,		0106200,	"asrb",
+0,		OP_SO,		006300,		"asl",
+0,		OP_SO,		0106300,	"aslb",
+0,		OP_SO,		006000,		"ror",
+0,		OP_SO,		0106000,	"rorb",
+0,		OP_SO,		006100,		"rol",
+0,		OP_SO,		0106100,	"rolb",
+0,		OP_SO,		000300,		"swab",
+0,		OP_SO,		005500,		"adc",
+0,		OP_SO,		0105500,	"adcb",
+0,		OP_SO,		005600,		"sbc",
+0,		OP_SO,		0105600,	"sbcb",
+0,		OP_SO,		006700,		"sxt",
+0,		OP_SO,		0100,		"jmp",
+0,		OP_DO,		010000,		"mov",
+0,		OP_DO,		0110000,	"movb",
+0,		OP_DO,		020000,		"cmp",
+0,		OP_DO,		0120000,	"cmpb",
+0,		OP_DO,		060000,		"add",
+0,		OP_DO,		0160000,	"sub",
+0,		OP_DO,		030000,		"bit",
+0,		OP_DO,		0130000,	"bitb",
+0,		OP_DO,		040000,		"bic",
+0,		OP_DO,		0140000,	"bicb",
+0,		OP_DO,		050000,		"bis",
+0,		OP_DO,		0150000,	"bisb",
+0,		OP_R_SO,	074000,		"xor",
+0,		JMP,		0100,		"jmp",
+0,		BR,		0400,		"br",
+0,		BR,		01000,		"bne",
+0,		BR,		01400,		"beq",
+0,		BR,		0100000,	"bpl",
+0,		BR,		0100400,	"bmi",
+0,		BR,		0102000,	"bvc",
+0,		BR,		0102400,	"bvs",
+0,		BR,		0103000,	"bcc",
+0,		BR,		0103400,	"bcs",
+0,		BR,		002000,		"bge",
+0,		BR,		002400,		"blt",
+0,		BR,		003000,		"bgt",
+0,		BR,		003400,		"ble",
+0,		BR,		0101000,	"bhi",
+0,		BR,		0101400,	"blos",
+0,		BR,		0103000,	"bhis",
+0,		BR,		0103400,	"blo",
+0,		EJMP,		0400,		"jbr",
+0,		EJMP,		01000,		"jne",
+0,		EJMP,		01400,		"jeq",
+0,		EJMP,		0100000,	"jpl",
+0,		EJMP,		0100400,	"jmi",
+0,		EJMP,		0102000,	"jvc",
+0,		EJMP,		0102400,	"jvs",
+0,		EJMP,		0103000,	"jcc",
+0,		EJMP,		0103400,	"jcs",
+0,		EJMP,		02000,		"jge",
+0,		EJMP,		02400,		"jlt",
+0,		EJMP,		03000,		"jgt",
+0,		EJMP,		03400,		"jle",
+0,		EJMP,		0101000,	"jhi",
+0,		EJMP,		0101400,	"jlos",
+0,		EJMP,		0103000,	"jhis",
+0,		EJMP,		0103400,	"jlo",
+0,		JSR,		004000,		"jsr",
+0,		RTS,		000200,		"rts",
+0,		MARK,		006400,		"mark",
+0,		SOB,		077000,		"sob",
+0,		SPL,		0230,		"spl",
+0,		TRAP,		0104000,	"emt",
+0,		TRAP,		0104400,	"trap",
+0,		TRAP,		0104400,	"sys",
+0,		OP_NO,		03,		"bpt",
+0,		OP_NO,		04,		"iot",
+0,		OP_NO,		02,		"rti",
+0,		OP_NO,		06,		"rtt",
+0,		OP_NO,		0,		"halt",
+0,		OP_NO,		01,		"wait",
+0,		OP_NO,		05,		"reset",
+0,		OP_NO,		0170000,	"cfcc",
+0,		OP_NO,		0170002,	"seti",
+0,		OP_NO,		0170012,	"setl",
+0,		OP_NO,		0170001,	"setf",
+0,		OP_NO,		0170011,	"setd",
+0,		CLEARCC,	0241,		"clc",
+0,		CLEARCC,	0242,		"clv",
+0,		CLEARCC,	0244,		"clz",
+0,		CLEARCC,	0250,		"cln",
+0,		SETCC,		0261,		"sec",
+0,		SETCC,		0262,		"sev",
+0,		SETCC,		0264,		"sez",
+0,		SETCC,		0270,		"sen",
+0,		OP_SO_R,	070000,		"mul",
+0,		OP_SO_R,	071000,		"div",
+0,		OP_SO_R,	072000,		"ash",
+0,		OP_SO_R,	073000,		"ashc",
+0,		MFP,		006500,		"mfpi",
+0,		MFP,		0106500,	"mfpd",
+0,		MFP,		006600,		"mtpi",
+0,		MFP,		0106600,	"mtpd",
+0,		FOP_FSO_FR,	0172000,	"addf",
+0,		FOP_FSO_FR,	0173000,	"subf",
+0,		FOP_FSO_FR,	0171000,	"mulf",
+0,		FOP_FSO_FR,	0174600,	"divf",
+0,		FOP_FSO_FR,	0173600,	"cmpf",
+0,		FOP_FSO_FR,	0171600,	"modf",
+0,		FOP_FSO,	0170400,	"clrf",
+0,		FOP_FSO,	0070700,	"negf",
+0,		FOP_FSO,	0170600,	"absf",
+0,		FOP_FSO,	0170500,	"tstf",
+0,		FOP_SO,		0170100,	"ldfps",
+0,		FOP_SO,		0170200,	"stfps",
+0,		FOP_SO,		0170300,	"stst",
+0,		MOVF,		0,		"movf",
+0,		FOP_SO_FR,	0177000,	"movif",
+0,		FOP_SO_FR,	0176400,	"movie",
+0,		FOP_FR_SO,	0175400,	"movfi",
+0,		FOP_FR_SO,	0175000,	"movei",
+0,		FOP_FSO_FR,	0177400,	"movof",
+0,		FOP_FR_FSO,	0176000,	"movfo",
diff --git a/mach/pdp/as/mach4.c b/mach/pdp/as/mach4.c
new file mode 100644
index 000000000..268868f5c
--- /dev/null
+++ b/mach/pdp/as/mach4.c
@@ -0,0 +1,163 @@
+#define RCSID4 "$Header$"
+
+/*
+ * (c) copyright 1983 by the Vrije Universiteit, Amsterdam, The Netherlands.
+ *
+ *          This product is part of the Amsterdam Compiler Kit.
+ *
+ * Permission to use, sell, duplicate or disclose this software must be
+ * obtained in writing. Requests for such permissions may be sent to
+ *
+ *      Dr. Andrew S. Tanenbaum
+ *      Wiskundig Seminarium
+ *      Vrije Universiteit
+ *      Postbox 7161
+ *      1007 MC Amsterdam
+ *      The Netherlands
+ *
+ */
+
+/*
+ * PDP 11 dependent yacc table
+ */
+
+operation
+	: OP_SO opr1
+		{ emit2( $1 | $2 ); op1($2); }
+	| OP_DO opr1 ',' opr2
+		{ emit2( $1 | ($2 << 6) | $4); op1($2); op2($4);}
+	| OP_R_SO REG ',' opr1
+		{ emit2( $1 | ($2 << 6) | $4); op1($4); }
+	| BR expr
+		{ branch( $1, $2); }
+	| EJMP expr
+		{ ejump( $1, $2); }
+	| JMP opr1
+		{ jump( $1, $2); }
+	| JSR REG ',' opr1
+		{ emit2( $1 | ($2 << 6) | $4); op1($4); }
+	| RTS REG
+		{ emit2($1 | $2); }
+	| MARK absexp
+		{ fit(fit6($2)); emit2($1 | $2); }
+	| SOB REG ',' expr
+		{ sob($2, $4); }
+	| SPL absexp
+		{ fit(fit3($2)); emit2( $1 | $2 ); }
+	| TRAP absexp
+		{ fit(fit8($2)); emit2( $1 | $2 ); }
+	| OP_NO
+		{emit2($1); }
+	| clcc
+		{ emit2($1); }
+	| secc
+		{ emit2($1); }
+	| OP_SO_R opr1 ',' REG
+		{ emit2( $1 | ($4 << 6) | $2); op1($2); }
+	| MFP opr1
+		{ emit2( $1 | $2); op1($2); }
+	| FOP_FSO_FR fopr1 ',' fregister
+		{emit2($1 | ($4 << 6) | $2); op1($2); }
+	| FOP_FSO fopr1
+		{ emit2( $1 | $2); op1($2); }
+	| FOP_SO opr1
+		{ emit2( $1 | $2); op1($2); }
+	| MOVF fop2 ',' fregister
+		{ emit2(OPSTF | ($4 << 6) | $2); op2($2);}
+	| MOVF fregister ',' fopr1
+		{ emit2(OPLDF | ($2 << 6) | $4); op1($4); }
+	| FOP_SO_FR opr1 ',' fregister
+		{ emit2($1 | ($4 << 6) | $2); op1($2); }
+	| FOP_FR_SO fregister ',' opr1
+		{ emit2($1 | ($2 << 6) | $4); op1($4); }
+	| FOP_FR_FSO fregister ',' fopr1
+		{ emit2($1 | ($2 << 6) | $4); op1($4); }
+	;
+clcc
+	: CLEARCC
+	| clcc '|' CLEARCC
+		{ $$ = ( $1 | $3 ); }
+	;
+secc
+	: SETCC
+	| secc '|' SETCC
+		{ $$ = ( $1 | $3 ); }
+	;
+opr1
+	: opr2
+		{ $$ = $1;
+		  exp_1 = exp_2;
+		  RELOMOVE(rel_1, rel_2);
+		  im1flag = im2flag;
+		  im2flag=0;
+		}
+	;
+opr2
+	: REG
+	| op2
+	;
+op2
+	: ari
+		{ $$ = ( RDEFMODE | $1); }
+	| ainc
+		{ $$ = ( AIMODE | $1 ); }
+	| adec
+		{ $$ = ( ADMODE | $1 ); }
+	| expr ari
+		{ exp_2 = $1; $$ = ( INDMODE | $2); im2flag = 1;
+		  RELOMOVE(rel_2, relonami);
+		}
+	| '*' expr ari
+		{ exp_2 = $2; $$ = ( INDDEFMODE | $3); im2flag = 1;
+		  RELOMOVE(rel_2, relonami);
+		}
+	| '*' ainc
+		{ $$ = ( AIDEFMODE | $2 ); }
+	| '*' adec
+		{ $$ = ( ADDEFMODE | $2 ); }
+	| expr
+		{ exp_2 = $1; $$ = (INDMODE | 07); im2flag = 1; 
+		  RELOMOVE(rel_2, relonami);
+		}
+	| '$' expr
+		{ exp_2 =$2; $$ = ( AIMODE | 07); im2flag = 1; 
+		  RELOMOVE(rel_2, relonami);
+		}
+	| '*' '$' expr
+		{ exp_2 = $3; $$ = ( AIDEFMODE | 07 ); im2flag = 1; 
+		  RELOMOVE(rel_2, relonami);
+		}
+	| '*' expr
+		{ exp_2 = $2; $$ = ( INDDEFMODE | 07 ); im2flag = 1; 
+		  RELOMOVE(rel_2, relonami);
+		}
+	;
+fopr1
+	: fopr2
+		{ $$ = $1; exp_1 = exp_2; im1flag = im2flag; im2flag=0;
+		  RELOMOVE(rel_1, rel_2);
+		}
+	;
+fopr2
+	: fregister
+	| fop2
+	;
+fop2
+	: FRSP
+	| op2
+	;
+ari
+	: '(' REG ')'
+		{ $$ = $2; }
+	;
+ainc
+	: ari '+'
+	;
+adec
+	: '-' ari
+		{ $$ = $2; }
+	;
+fregister
+	: FREG
+	| REG
+	;
diff --git a/mach/pdp/as/mach5.c b/mach/pdp/as/mach5.c
new file mode 100644
index 000000000..7bedc8712
--- /dev/null
+++ b/mach/pdp/as/mach5.c
@@ -0,0 +1,133 @@
+#define RCSID5 "$Header$"
+
+/*
+ * (c) copyright 1983 by the Vrije Universiteit, Amsterdam, The Netherlands.
+ *
+ *          This product is part of the Amsterdam Compiler Kit.
+ *
+ * Permission to use, sell, duplicate or disclose this software must be
+ * obtained in writing. Requests for such permissions may be sent to
+ *
+ *      Dr. Andrew S. Tanenbaum
+ *      Wiskundig Seminarium
+ *      Vrije Universiteit
+ *      Postbox 7161
+ *      1007 MC Amsterdam
+ *      The Netherlands
+ *
+ */
+
+op1(mode)	{
+	int relpc = 0;
+	if (im1flag)	{
+		if (mode == 067 || mode == 077) {
+			exp_1.val = adjust(exp_1);
+			relpc = RELPC;
+		}
+#ifdef RELOCATION
+		RELOMOVE(relonami, rel_1);
+		if (rflag != 0 && PASS_RELO)
+			newrelo(exp_1.typ, RELO2|relpc);
+#endif
+		emit2(exp_1.val);
+		im1flag = 0;
+	}
+}
+
+op2(mode)	{
+	int relpc = 0;
+	if (im2flag)	{
+		if (mode == 067 || mode == 077) {
+			relpc = RELPC;
+			exp_2.val = adjust(exp_2);
+		}
+#ifdef RELOCATION
+		RELOMOVE(relonami, rel_2);
+		if (rflag != 0 && PASS_RELO)
+			newrelo(exp_2.typ, RELO2|relpc);
+#endif
+		emit2(exp_2.val);
+		im2flag = 0;
+	}
+}
+
+branch(opc,exp) expr_t exp; {
+	register eval;
+	register sm;
+
+	eval = adjust(exp) >> 1;
+	sm = fitb(eval);
+	if ((exp.typ & ~S_DOT) != DOTTYP && pass >= PASS_2) sm = 0;
+	if (!sm && pass >= PASS_2) {
+		serror("label too far");
+	}
+	emit2(opc | lowb(eval));
+}
+
+ejump(opc, exp) expr_t exp; {
+	register sm,eval;
+	int gain;
+
+# ifdef THREE_PASS
+	eval = adjust(exp) >> 1;
+	sm = fitb(eval);
+	if ((exp.typ & ~S_DOT) != DOTTYP)	{
+		sm = 0;
+	}
+	gain = (opc == OPBRA ? 2 : 4);
+	if (small(sm,gain))	{
+		emit2( opc | lowb(eval));
+	}
+	else	{
+# endif
+		if (opc != OPBRA)	{
+			emit2((opc^0400) | 04);
+		}
+
+		exp_1.val = exp.val;
+		im1flag = 1;
+		jump(0100,067);
+# ifdef THREE_PASS
+	}
+# endif
+}
+
+sob(reg, exp) expr_t exp; {
+	if ((exp.typ & ~S_DOT) != DOTTYP)	{
+		serror("error in sob-label");
+	}
+	exp.val = ( - adjust(exp) ) >> 1;
+	fit(fit6(exp.val));
+	emit2( OPSOB | (reg << 6) | exp.val);
+}
+
+jump(opc,opr)	{
+	register sm;
+	register val;
+
+	if (opr==067) {
+# ifdef THREE_PASS
+		val = adjust(exp_1) >> 1;
+		if ( fitb(val) && (exp_1.typ & ~S_DOT) == DOTTYP) {
+			sm = 1;
+		}
+		if (small(sm,2)) {
+			emit2(OPBRA | lowb(val));
+			im1flag = 0;
+			return(0);
+		}
+# endif
+	}
+	emit2(opc | opr);
+	op1(opr);
+}
+
+valu_t adjust(exp) expr_t exp; {
+	valu_t val;
+
+	val = exp.val - DOTVAL - 2;
+# ifdef THREE_PASS
+	if (pass == PASS_2 && val > 0) val -= DOTGAIN;
+# endif
+	return(val);
+}