diff --git a/src/cmd/gc/go.h b/src/cmd/gc/go.h
index b04790d662..6dc8393bd7 100644
--- a/src/cmd/gc/go.h
+++ b/src/cmd/gc/go.h
@@ -37,13 +37,12 @@ enum
 	PRIME10		= 10093,
 
 	AUNK		= 100,
+
 	// these values are known by runtime
-	ASIMP		= 0,
+	AMEM		= 0,
+	ANOEQ,
 	ASTRING,
-	APTR,
 	AINTER,
-	ASLICE,
-	ASTRUCT,
 
 	BADWIDTH	= -1000000000
 };
diff --git a/src/cmd/gc/subr.c b/src/cmd/gc/subr.c
index 0650a634e3..bfcdd08f5b 100644
--- a/src/cmd/gc/subr.c
+++ b/src/cmd/gc/subr.c
@@ -291,26 +291,16 @@ algtype(Type *t)
 {
 	int a;
 
-	a = AUNK;
-	if(issimple[t->etype])
-		a = ASIMP;	// simple mem
+	if(issimple[t->etype] || isptr[t->etype] || t->etype == TCHAN)
+		a = AMEM;	// just bytes (int, ptr, etc)
 	else
 	if(t->etype == TSTRING)
 		a = ASTRING;	// string
 	else
-	if(isptr[simtype[t->etype]])
-		a = APTR;	// pointer
-	else
-	if(isslice(t))
-		a = ASLICE;
-	else
-	if(t->etype == TSTRUCT)
-		a = ASTRUCT;
-	else
-	if(isinter(t))
+	if(t->etype == TINTER)
 		a = AINTER;	// interface
-//	else
-//		fatal("algtype: cant find type %T", t);
+	else
+		a = ANOEQ;	// just bytes, but no hash/eq
 	return a;
 }
 
diff --git a/src/runtime/chan.c b/src/runtime/chan.c
index 929d07f7ea..6f89fa3953 100644
--- a/src/runtime/chan.c
+++ b/src/runtime/chan.c
@@ -88,17 +88,9 @@ sys·newchan(uint32 elemsize, uint32 elemalg, uint32 hint,
 	Hchan *c;
 	int32 i;
 
-	switch(elemalg){
-	case ASIMP:
-	case ASTRING:
-	case APTR:
-	case AINTER:
-	case AARRAY:
-	case ASTRUCT:
-		break;
-	default:
+	if(elemalg >= nelem(algarray)) {
 		printf("chan(alg=%d)\n", elemalg);
-		throw("sys·newchan: unsupported channel element type");
+		throw("sys·newchan: unsupported elem type");
 	}
 
 	c = mal(sizeof(*c));
diff --git a/src/runtime/hashmap.c b/src/runtime/hashmap.c
index 5be990c49c..f54d13197c 100644
--- a/src/runtime/hashmap.c
+++ b/src/runtime/hashmap.c
@@ -663,28 +663,12 @@ sys·newmap(uint32 keysize, uint32 valsize,
 {
 	Hmap *h;
 
-	switch(keyalg) {
-	case ASIMP:
-	case ASTRING:
-	case APTR:
-	case AINTER:
-	case AARRAY:
-	case ASTRUCT:
-		break;
-	default:
+	if(keyalg >= nelem(algarray) || algarray[keyalg].hash == nohash) {
 		printf("map(keyalg=%d)\n", keyalg);
 		throw("sys·newmap: unsupported map key type");
 	}
 
-	switch(valalg) {
-	case ASIMP:
-	case ASTRING:
-	case APTR:
-	case AINTER:
-	case AARRAY:
-	case ASTRUCT:
-		break;
-	default:
+	if(valalg >= nelem(algarray)) {
 		printf("map(valalg=%d)\n", valalg);
 		throw("sys·newmap: unsupported map value type");
 	}
diff --git a/src/runtime/iface.c b/src/runtime/iface.c
index 70e2b4f04c..99116806a3 100644
--- a/src/runtime/iface.c
+++ b/src/runtime/iface.c
@@ -404,11 +404,32 @@ sys·ifaceI2I2(Sigi *si, Iface i, Iface ret, bool ok)
 	FLUSH(&ok);
 }
 
-// ifaceeq(i1 any, i2 any) (ret bool);
-void
-sys·ifaceeq(Iface i1, Iface i2, bool ret)
+uint64
+ifacehash(Iface a)
 {
 	int32 alg, wid;
+	
+	if(a.type == nil)
+		return 0;
+	alg = a.type->sigt->hash;
+	wid = a.type->sigt->offset;
+	if(algarray[alg].hash == nohash) {
+		// calling nohash will throw too,
+		// but we can print a better error.
+		printf("hash of unhashable type %s\n", a.type->sigt->name);
+		throw("interface hash");
+	}
+	if(wid <= sizeof a.data)
+		return algarray[alg].hash(wid, &a.data);
+	else
+		return algarray[alg].hash(wid, a.data);
+}
+
+bool
+ifaceeq(Iface i1, Iface i2)
+{
+	int32 alg, wid;
+	bool ret;
 
 	if(iface_debug) {
 		prints("Ieq i1=");
@@ -438,6 +459,13 @@ sys·ifaceeq(Iface i1, Iface i2, bool ret)
 	if(wid != i2.type->sigt->offset)
 		goto no;
 
+	if(algarray[alg].equal == noequal) {
+		// calling noequal will throw too,
+		// but we can print a better error.
+		printf("comparing uncomparable type %s\n", i1.type->sigt->name);
+		throw("interface compare");
+	}
+
 	if(wid <= sizeof i1.data) {
 		if(!algarray[alg].equal(wid, &i1.data, &i2.data))
 			goto no;
@@ -454,6 +482,14 @@ no:
 		sys·printbool(ret);
 		prints("\n");
 	}
+	return ret;
+}
+
+// ifaceeq(i1 any, i2 any) (ret bool);
+void
+sys·ifaceeq(Iface i1, Iface i2, bool ret)
+{
+	ret = ifaceeq(i1, i2);
 	FLUSH(&ret);
 }
 
@@ -526,7 +562,7 @@ fakesigt(string type, bool indir)
 	sigt = mal(2*sizeof sigt[0]);
 	sigt[0].name = mal(type->len + 1);
 	mcpy(sigt[0].name, type->str, type->len);
-	sigt[0].hash = ASIMP;	// alg
+	sigt[0].hash = AMEM;	// alg
 	if(indir)
 		sigt[0].offset = 2*sizeof(niliface.data);  // big width
 	else
diff --git a/src/runtime/runtime.c b/src/runtime/runtime.c
index 29a67b190d..ce9349383c 100644
--- a/src/runtime/runtime.c
+++ b/src/runtime/runtime.c
@@ -328,57 +328,52 @@ strprint(uint32 s, string *a)
 	sys·printstring(*a);
 }
 
-static void
-strcopy(uint32 s, string *a, string *b)
+static uint64
+interhash(uint32 s, Iface *a)
 {
 	USED(s);
-	if(b == nil) {
-		*a = nil;
-		return;
-	}
-	*a = *b;
+	return ifacehash(*a);
 }
 
-static uint64
-ptrhash(uint32 s, void **a)
+static void
+interprint(uint32 s, Iface *a)
 {
-	return memhash(s, *a);
+	USED(s);
+	sys·printinter(*a);
 }
 
 static uint32
-ptrequal(uint32 s, void **a, void **b)
+interequal(uint32 s, Iface *a, Iface *b)
 {
-	USED(s, a, b);
-	prints("ptrequal\n");
+	USED(s);
+	return ifaceeq(*a, *b);
+}
+
+uint64
+nohash(uint32 s, void *a)
+{
+	USED(s);
+	USED(a);
+	throw("hash of unhashable type");
 	return 0;
 }
 
-static void
-ptrprint(uint32 s, void **a)
-{
-	USED(s, a);
-	prints("ptrprint\n");
-}
-
-static void
-ptrcopy(uint32 s, void **a, void **b)
+uint32
+noequal(uint32 s, void *a, void *b)
 {
 	USED(s);
-	if(b == nil) {
-		*a = nil;
-		return;
-	}
-	*a = *b;
+	USED(a);
+	USED(b);
+	throw("comparing uncomparable types");
+	return 0;
 }
 
 Alg
 algarray[] =
 {
-[ASIMP]		{ memhash, memequal, memprint, memcopy },
-[ASTRING]	{ strhash, strequal, strprint, strcopy },
-[APTR]		{ memhash, memequal, memprint, memcopy },	// TODO: ptr routines
-[AINTER]	{ memhash, memequal, memprint, memcopy },	// TODO: interface routines
-[ASTRUCT]	{ memhash, memequal, memprint, memcopy },	// TODO: what goes here?
-[AARRAY]	{ memhash, memequal, memprint, memcopy },	// TODO: what goes here?
+[AMEM]	{ memhash, memequal, memprint, memcopy },
+[ANOEQ]	{ nohash, noequal, memprint, memcopy },
+[ASTRING]	{ strhash, strequal, strprint, memcopy },
+[AINTER]		{ interhash, interequal, interprint, memcopy },
 };
 
diff --git a/src/runtime/runtime.h b/src/runtime/runtime.h
index bc6b2f76d5..47103e253a 100644
--- a/src/runtime/runtime.h
+++ b/src/runtime/runtime.h
@@ -226,18 +226,17 @@ struct	Func
  */
 enum
 {
-	ASIMP		= 0,
+	AMEM,
+	ANOEQ,
 	ASTRING,
-	APTR,
 	AINTER,
-	AARRAY,
-	ASTRUCT,
+	Amax
 };
 
 /*
  * external data
  */
-extern	Alg	algarray[];
+extern	Alg	algarray[Amax];
 extern	string	emptystring;
 G*	allg;
 int32	goidgen;
@@ -299,6 +298,10 @@ void*	stackalloc(uint32);
 void	stackfree(void*);
 MCache*	allocmcache(void);
 void	mallocinit(void);
+bool	ifaceeq(Iface, Iface);
+uint64	ifacehash(Iface);
+uint64	nohash(uint32, void*);
+uint32	noequal(uint32, void*, void*);
 
 #pragma	varargck	argpos	printf	1
 
@@ -366,6 +369,7 @@ void	notewakeup(Note*);
 #define sys_printfloat sys·printfloat
 #define sys_printhex sys·printhex
 #define sys_printint sys·printint
+#define sys_printinter sys·printinter
 #define sys_printpc sys·printpc
 #define sys_printpointer sys·printpointer
 #define sys_printstring sys·printstring
@@ -393,6 +397,7 @@ void*	sys_getcallerpc(void*);
 void	sys_printbool(bool);
 void	sys_printfloat(float64);
 void	sys_printint(int64);
+void	sys_printinter(Iface);
 void	sys_printstring(string);
 void	sys_printpc(void*);
 void	sys_printpointer(void*);
diff --git a/test/bigalg.go b/test/bigalg.go
index 434eecf5d2..afeccdf8f0 100644
--- a/test/bigalg.go
+++ b/test/bigalg.go
@@ -62,25 +62,6 @@ func maptest() {
 	}
 }
 
-var mt1 = make(map[T]int)
-var ma1 = make(map[[]int] int)
-
-func maptest2() {
-	mt1[t] = 123;
-	t1 := t;
-	val, ok := mt1[t1];
-	if val != 123 || !ok {
-		println("fail: map key struct", val, ok);
-	}
-
-	ma1[a] = 345;
-	a1 := a;
-	val, ok = ma1[a1];
-	if val != 345 || !ok {
-		panic("map key array", val, ok);
-	}
-}
-
 var ct = make(chan T)
 var ca = make(chan []int)
 
@@ -136,7 +117,6 @@ func interfacetest() {
 func main() {
 	arraycmptest();
 	maptest();
-	maptest2();
 	chantest();
 	interfacetest();
 }
diff --git a/test/cmp1.go b/test/cmp1.go
new file mode 100644
index 0000000000..82e932f45e
--- /dev/null
+++ b/test/cmp1.go
@@ -0,0 +1,66 @@
+// $G $D/$F.go && $L $F.$A && ./$A.out
+
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+import "unsafe"
+
+func use(bool) { }
+
+func stringptr(s string) uintptr {
+	return *(&s).(unsafe.Pointer).(*uintptr);
+}
+
+func isfalse(b bool) {
+	if b { panicln("wanted false, got true") } // stack will explain where
+}
+
+func istrue(b bool) {
+	if !b { panicln("wanted true, got false") } // stack will explain where
+}
+
+func main()
+{
+	var a []int;
+	var b map[string]int;
+
+	var c string = "hello";
+	var d string = "hel";	// try to get different pointer
+	d = d + "lo";
+	if stringptr(c) == stringptr(d) {
+		panic("compiler too smart -- got same string")
+	}
+
+	var e = make(chan int);
+
+	var ia interface{} = a;
+	var ib interface{} = b;
+	var ic interface{} = c;
+	var id interface{} = d;
+	var ie interface{} = e;
+
+	// these comparisons are okay because
+	// string compare is okay and the others
+	// are comparisons where the types differ.
+	isfalse(ia == ib);
+	isfalse(ia == ic);
+	isfalse(ia == id);
+	isfalse(ib == ic);
+	isfalse(ib == id);
+	istrue(ic == id);
+	istrue(ie == ie);
+
+	// map of interface should use == on interface values,
+	// not memory.
+	// TODO: should m[c], m[d] be valid here?
+	var m = make(map[interface{}] int);
+	m[ic] = 1;
+	m[id] = 2;
+	if m[ic] != 2 {
+		panic("m[ic] = ", m[ic]);
+	}
+}
+
diff --git a/test/cmp2.go b/test/cmp2.go
new file mode 100644
index 0000000000..d43cfcd107
--- /dev/null
+++ b/test/cmp2.go
@@ -0,0 +1,16 @@
+// $G $D/$F.go && $L $F.$A && ! ./$A.out
+
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+func use(bool) { }
+
+func main()
+{
+	var a []int;
+	var ia interface{} = a;
+	use(ia == ia);
+}
diff --git a/test/cmp3.go b/test/cmp3.go
new file mode 100644
index 0000000000..06a67bdf05
--- /dev/null
+++ b/test/cmp3.go
@@ -0,0 +1,16 @@
+// $G $D/$F.go && $L $F.$A && ! ./$A.out
+
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+func use(bool) { }
+
+func main()
+{
+	var b map[string]int;
+	var ib interface{} = b;
+	use(ib == ib);
+}
diff --git a/test/cmp4.go b/test/cmp4.go
new file mode 100644
index 0000000000..61787b07c4
--- /dev/null
+++ b/test/cmp4.go
@@ -0,0 +1,15 @@
+// $G $D/$F.go && $L $F.$A && ! ./$A.out
+
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+func main()
+{
+	var a []int;
+	var ia interface{} = a;
+	var m = make(map[interface{}] int);
+	m[ia] = 1;
+}
diff --git a/test/cmp5.go b/test/cmp5.go
new file mode 100644
index 0000000000..7500974223
--- /dev/null
+++ b/test/cmp5.go
@@ -0,0 +1,15 @@
+// $G $D/$F.go && $L $F.$A && ! ./$A.out
+
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+func main()
+{
+	var b map[string]int;
+	var ib interface{} = b;
+	var m = make(map[interface{}] int);
+	m[ib] = 1;
+}
diff --git a/test/golden.out b/test/golden.out
index 023b96edd0..163242bc23 100644
--- a/test/golden.out
+++ b/test/golden.out
@@ -1,4 +1,36 @@
 
+=========== ./cmp2.go
+comparing uncomparable type []int
+throw: interface compare
+SIGSEGV: segmentation violation
+Faulting address: 0x0
+pc: xxx
+
+
+=========== ./cmp3.go
+comparing uncomparable type map[string] int
+throw: interface compare
+SIGSEGV: segmentation violation
+Faulting address: 0x0
+pc: xxx
+
+
+=========== ./cmp4.go
+hash of unhashable type []int
+throw: interface hash
+SIGSEGV: segmentation violation
+Faulting address: 0x0
+pc: xxx
+
+
+=========== ./cmp5.go
+hash of unhashable type map[string] int
+throw: interface hash
+SIGSEGV: segmentation violation
+Faulting address: 0x0
+pc: xxx
+
+
 =========== ./convlit.go
 BUG: errchk: ./convlit.go: missing expected error message on line 16: 'conver|incompatible'
 errchk: ./convlit.go: missing expected error message on line 22: 'convert'
diff --git a/test/map.go b/test/map.go
index 51c6fe5f5b..085502bf52 100644
--- a/test/map.go
+++ b/test/map.go
@@ -52,7 +52,7 @@ func main() {
 	mipT := make(map[int] *T);
 	mpTi := make(map[*T] int);
 	mit := make(map[int] T);
-	mti := make(map[T] int);
+//	mti := make(map[T] int);
 
 	type M map[int] int;
 	mipM := make(map[int] M);
@@ -88,7 +88,7 @@ func main() {
 		mpTi[apT[i]] = i;
 		mipM[i] = m;
 		mit[i] = t;
-		mti[t] = i;
+	//	mti[t] = i;
 	}
 
 	// test len
@@ -122,15 +122,15 @@ func main() {
 	if len(mpTi) != count {
 		fmt.Printf("len(mpTi) = %d\n", len(mpTi));
 	}
-	if len(mti) != count {
-		fmt.Printf("len(mti) = %d\n", len(mti));
-	}
+//	if len(mti) != count {
+//		fmt.Printf("len(mti) = %d\n", len(mti));
+//	}
 	if len(mipM) != count {
 		fmt.Printf("len(mipM) = %d\n", len(mipM));
 	}
-	if len(mti) != count {
-		fmt.Printf("len(mti) = %d\n", len(mti));
-	}
+//	if len(mti) != count {
+//		fmt.Printf("len(mti) = %d\n", len(mti));
+//	}
 	if len(mit) != count {
 		fmt.Printf("len(mit) = %d\n", len(mit));
 	}
@@ -174,15 +174,15 @@ func main() {
 		if(mpTi[apT[i]] != i) {
 			fmt.Printf("mpTi[apT[%d]] = %d\n", i, mpTi[apT[i]]);
 		}
-		if(mti[t] != i) {
-			fmt.Printf("mti[%s] = %s\n", s, mti[t]);
-		}
+	//	if(mti[t] != i) {
+	//		fmt.Printf("mti[%s] = %s\n", s, mti[t]);
+	//	}
 		if (mipM[i][i] != i + 1) {
 			fmt.Printf("mipM[%d][%d] = %d\n", i, i, mipM[i][i]);
 		}
-		if(mti[t] != i) {
-			fmt.Printf("mti[%v] = %d\n", t, mti[t]);
-		}
+	//	if(mti[t] != i) {
+	//		fmt.Printf("mti[%v] = %d\n", t, mti[t]);
+	//	}
 		if(mit[i].i != int64(i) || mit[i].f != f) {
 			fmt.Printf("mit[%d] = {%d %g}\n", i, mit[i].i, mit[i].f);
 		}
@@ -314,16 +314,16 @@ func main() {
 				fmt.Printf("tuple existence assign: mit[%d]\n", i);
 			}
 		}
-		{
-			a, b := mti[t];
-			if !b {
-				fmt.Printf("tuple existence decl: mti[%d]\n", i);
-			}
-			a, b = mti[t];
-			if !b {
-				fmt.Printf("tuple existence assign: mti[%d]\n", i);
-			}
-		}
+//		{
+//			a, b := mti[t];
+//			if !b {
+//				fmt.Printf("tuple existence decl: mti[%d]\n", i);
+//			}
+//			a, b = mti[t];
+//			if !b {
+//				fmt.Printf("tuple existence assign: mti[%d]\n", i);
+//			}
+//		}
 	}
 
 	// test nonexistence with tuple check
@@ -442,16 +442,16 @@ func main() {
 				fmt.Printf("tuple nonexistence assign: mipM[%d]", i);
 			}
 		}
-		{
-			a, b := mti[t];
-			if b {
-				fmt.Printf("tuple nonexistence decl: mti[%d]", i);
-			}
-			a, b = mti[t];
-			if b {
-				fmt.Printf("tuple nonexistence assign: mti[%d]", i);
-			}
-		}
+//		{
+//			a, b := mti[t];
+//			if b {
+//				fmt.Printf("tuple nonexistence decl: mti[%d]", i);
+//			}
+//			a, b = mti[t];
+//			if b {
+//				fmt.Printf("tuple nonexistence assign: mti[%d]", i);
+//			}
+//		}
 		{
 			a, b := mit[i];
 			if b {