diff --git a/Makefile b/Makefile
index dd2e83985e..4c50787f2d 100755
--- a/Makefile
+++ b/Makefile
@@ -51,7 +51,6 @@ DLL_OBJS = $(PLAF_DLL_OBJS) \
 	vm/inline_cache.o \
 	vm/io.o \
 	vm/jit.o \
-	vm/local_roots.o \
 	vm/math.o \
 	vm/primitives.o \
 	vm/profiler.o \
@@ -61,8 +60,7 @@ DLL_OBJS = $(PLAF_DLL_OBJS) \
 	vm/tuples.o \
 	vm/utilities.o \
         vm/vm.o \
-	vm/words.o \
-	vm/write_barrier.o
+	vm/words.o
 
 EXE_OBJS = $(PLAF_EXE_OBJS)
 
diff --git a/vm/data_gc.cpp b/vm/data_gc.cpp
index b3836e4a3b..dfe5ef3365 100755
--- a/vm/data_gc.cpp
+++ b/vm/data_gc.cpp
@@ -76,19 +76,20 @@ template<typename Strategy> object *factor_vm::promote_object(object *untagged,
 	return newpointer;
 }
 
-template<typename Strategy> void factor_vm::trace_card(card *ptr, cell here, Strategy &strategy)
+template<typename Strategy> void factor_vm::trace_card(card *ptr, old_space *gen, Strategy &strategy)
 {
-	cell card_scan = card_to_addr(ptr) + card_offset(ptr);
+	cell card_start = card_to_addr(ptr);
+	cell card_scan = card_start + gen->card_offset(card_start);
 	cell card_end = card_to_addr(ptr + 1);
 
-	if(here < card_end) card_end = here;
+	if(gen->here < card_end) card_end = gen->here;
 
 	strategy.copy_reachable_objects(card_scan,&card_end);
 
 	gc_stats.cards_scanned++;
 }
 
-template<typename Strategy> void factor_vm::trace_card_deck(card_deck *deck, cell here, card mask, card unmask, Strategy &strategy)
+template<typename Strategy> void factor_vm::trace_card_deck(card_deck *deck, old_space *gen, card mask, card unmask, Strategy &strategy)
 {
 	card *first_card = deck_to_card(deck);
 	card *last_card = deck_to_card(deck + 1);
@@ -107,7 +108,7 @@ template<typename Strategy> void factor_vm::trace_card_deck(card_deck *deck, cel
 			{
 				if(ptr[card] & mask)
 				{
-					trace_card(&ptr[card],here,strategy);
+					trace_card(&ptr[card],gen,strategy);
 					ptr[card] &= ~unmask;
 				}
 			}
@@ -118,7 +119,7 @@ template<typename Strategy> void factor_vm::trace_card_deck(card_deck *deck, cel
 }
 
 /* Trace all objects referenced from marked cards */
-template<typename Strategy> void factor_vm::trace_cards(cell gen, zone *z, Strategy &strategy)
+template<typename Strategy> void factor_vm::trace_cards(cell gen, old_space *z, Strategy &strategy)
 {
 	u64 start_time = current_micros();
 
@@ -179,7 +180,7 @@ template<typename Strategy> void factor_vm::trace_cards(cell gen, zone *z, Strat
 	{
 		if(*ptr & mask)
 		{
-			trace_card_deck(ptr,z->here,mask,unmask,strategy);
+			trace_card_deck(ptr,z,mask,unmask,strategy);
 			*ptr &= ~unmask;
 		}
 	}
@@ -398,10 +399,10 @@ void factor_vm::update_dirty_code_blocks()
 }
 
 template<typename Strategy>
-copying_collector<Strategy>::copying_collector(factor_vm *myvm_, zone *newspace_)
-: myvm(myvm_), current_gc(myvm_->current_gc), newspace(newspace_)
+copying_collector<Strategy>::copying_collector(factor_vm *myvm_, old_space *target_)
+: myvm(myvm_), current_gc(myvm_->current_gc), target(target_)
 {
-	scan = newspace->here;
+	scan = target->here;
 }
 
 template<typename Strategy> Strategy &copying_collector<Strategy>::strategy()
@@ -411,14 +412,7 @@ template<typename Strategy> Strategy &copying_collector<Strategy>::strategy()
 
 template<typename Strategy> object *copying_collector<Strategy>::allot(cell size)
 {
-	if(newspace->here + size <= newspace->end)
-	{
-		object *obj = newspace->allot(size);
-		myvm->allot_barrier(obj);
-		return obj;
-	}
-	else
-		return NULL;
+	return target->allot(size);
 }
 
 template<typename Strategy> object *copying_collector<Strategy>::copy_object(object *untagged)
@@ -440,13 +434,13 @@ template<typename Strategy> cell copying_collector<Strategy>::trace_next(cell sc
 
 template<typename Strategy> void copying_collector<Strategy>::go()
 {
-	strategy().copy_reachable_objects(scan,&newspace->here);
+	strategy().copy_reachable_objects(scan,&target->here);
 }
 
 struct nursery_collector : copying_collector<nursery_collector>
 {
-	explicit nursery_collector(factor_vm *myvm_, zone *newspace_) :
-		copying_collector<nursery_collector>(myvm_,newspace_) {}
+	explicit nursery_collector(factor_vm *myvm_, old_space *target_) :
+		copying_collector<nursery_collector>(myvm_,target_) {}
 
 	bool should_copy_p(object *untagged)
 	{
@@ -463,13 +457,13 @@ struct aging_collector : copying_collector<aging_collector>
 {
 	zone *tenured;
 
-	explicit aging_collector(factor_vm *myvm_, zone *newspace_) :
-		copying_collector<aging_collector>(myvm_,newspace_),
+	explicit aging_collector(factor_vm *myvm_, old_space *target_) :
+		copying_collector<aging_collector>(myvm_,target_),
 		tenured(myvm->data->tenured) {}
 
 	bool should_copy_p(object *untagged)
 	{
-		if(newspace->contains_p(untagged))
+		if(target->contains_p(untagged))
 			return false;
 		else
 			return !tenured->contains_p(untagged);
@@ -483,12 +477,12 @@ struct aging_collector : copying_collector<aging_collector>
 
 struct aging_again_collector : copying_collector<aging_again_collector>
 {
-	explicit aging_again_collector(factor_vm *myvm_, zone *newspace_) :
-		copying_collector<aging_again_collector>(myvm_,newspace_) {}
+	explicit aging_again_collector(factor_vm *myvm_, old_space *target_) :
+		copying_collector<aging_again_collector>(myvm_,target_) {}
 
 	bool should_copy_p(object *untagged)
 	{
-		return !newspace->contains_p(untagged);
+		return !target->contains_p(untagged);
 	}
 	
 	void copy_reachable_objects(cell scan, cell *end)
@@ -499,12 +493,12 @@ struct aging_again_collector : copying_collector<aging_again_collector>
 
 struct tenured_collector : copying_collector<tenured_collector>
 {
-	explicit tenured_collector(factor_vm *myvm_, zone *newspace_) :
-		copying_collector<tenured_collector>(myvm_,newspace_) {}
+	explicit tenured_collector(factor_vm *myvm_, old_space *target_) :
+		copying_collector<tenured_collector>(myvm_,target_) {}
 	
 	bool should_copy_p(object *untagged)
 	{
-		return !newspace->contains_p(untagged);
+		return !target->contains_p(untagged);
 	}
 	
 	void copy_reachable_objects(cell scan, cell *end)
@@ -791,7 +785,6 @@ object *factor_vm::allot_object(header header, cell size)
 			garbage_collection(tenured_gen,true,true,size);
 
 		obj = data->tenured->allot(size);
-		allot_barrier(obj);
 
 		/* Allows initialization code to store old->new pointers
 		without hitting the write barrier in the common case of
diff --git a/vm/data_gc.hpp b/vm/data_gc.hpp
index 68aab2f6b3..9032f6696d 100755
--- a/vm/data_gc.hpp
+++ b/vm/data_gc.hpp
@@ -66,10 +66,10 @@ struct gc_state {
 template<typename Strategy> struct copying_collector {
 	factor_vm *myvm;
 	gc_state *current_gc;
-	zone *newspace;
+	old_space *target;
 	cell scan;
 
-	explicit copying_collector(factor_vm *myvm_, zone *newspace);
+	explicit copying_collector(factor_vm *myvm_, old_space *target);
 	Strategy &strategy();
 	object *allot(cell size);
 	cell trace_next(cell scan);
diff --git a/vm/data_heap.cpp b/vm/data_heap.cpp
index 4fc9770c55..7e358cb2f9 100755
--- a/vm/data_heap.cpp
+++ b/vm/data_heap.cpp
@@ -6,7 +6,6 @@ namespace factor
 void factor_vm::init_card_decks()
 {
 	cell start = align(data->seg->start,deck_size);
-	allot_markers_offset = (cell)data->allot_markers - (start >> card_bits);
 	cards_offset = (cell)data->cards - (start >> card_bits);
 	decks_offset = (cell)data->decks - (start >> deck_bits);
 }
@@ -36,26 +35,17 @@ data_heap::data_heap(factor_vm *myvm, cell young_size_, cell aging_size_, cell t
 	decks = new char[decks_size];
 	decks_end = decks + decks_size;
 
-	allot_markers = new char[cards_size];
-	allot_markers_end = allot_markers + cards_size;
+	cell start = align(seg->start,deck_size);
 
-	cell alloter = align(seg->start,deck_size);
+	tenured = new old_space(tenured_size,start);
+	tenured_semispace = new old_space(tenured_size,tenured->end);
 
-	tenured = new zone;
-	tenured_semispace = new zone;
-	alloter = tenured->init_zone(tenured_size,alloter);
-	alloter = tenured_semispace->init_zone(tenured_size,alloter);
+	aging = new old_space(aging_size,tenured_semispace->end);
+	aging_semispace = new old_space(aging_size,aging->end);
 
-	aging = new zone;
-	aging_semispace = new zone;
-	alloter = aging->init_zone(aging_size,alloter);
-	alloter = aging_semispace->init_zone(aging_size,alloter);
+	nursery = new zone(young_size,aging_semispace->end);
 
-	nursery = new zone;
-	alloter = nursery->init_zone(young_size,alloter);
-
-	if(seg->end - alloter > deck_size)
-		critical_error("Bug in alloc_data_heap",alloter);
+	assert(seg->end - nursery->end <= deck_size);
 }
 
 data_heap::~data_heap()
@@ -66,7 +56,6 @@ data_heap::~data_heap()
 	delete aging_semispace;
 	delete tenured;
 	delete tenured_semispace;
-	delete[] allot_markers;
 	delete[] cards;
 	delete[] decks;
 }
@@ -81,7 +70,7 @@ data_heap *factor_vm::grow_data_heap(data_heap *data, cell requested_bytes)
 		new_tenured_size);
 }
 
-void factor_vm::clear_cards(zone *gen)
+void factor_vm::clear_cards(old_space *gen)
 {
 	/* NOTE: reverse order due to heap layout. */
 	card *first_card = addr_to_card(gen->start);
@@ -89,7 +78,7 @@ void factor_vm::clear_cards(zone *gen)
 	memset(first_card,0,last_card - first_card);
 }
 
-void factor_vm::clear_decks(zone *gen)
+void factor_vm::clear_decks(old_space *gen)
 {
 	/* NOTE: reverse order due to heap layout. */
 	card_deck *first_deck = addr_to_deck(gen->start);
@@ -97,23 +86,16 @@ void factor_vm::clear_decks(zone *gen)
 	memset(first_deck,0,last_deck - first_deck);
 }
 
-void factor_vm::clear_allot_markers(zone *gen)
-{
-	card *first_card = addr_to_allot_marker((object *)gen->start);
-	card *last_card = addr_to_allot_marker((object *)gen->end);
-	memset(first_card,invalid_allot_marker,last_card - first_card);
-}
-
 /* After garbage collection, any generations which are now empty need to have
 their allocation pointers and cards reset. */
-void factor_vm::reset_generation(zone *gen)
+void factor_vm::reset_generation(old_space *gen)
 {
 	gen->here = gen->start;
 	if(secure_gc) memset((void*)gen->start,69,gen->size);
 
 	clear_cards(gen);
 	clear_decks(gen);
-	clear_allot_markers(gen);
+	gen->clear_allot_markers();
 }
 
 void factor_vm::set_data_heap(data_heap *data_)
diff --git a/vm/data_heap.hpp b/vm/data_heap.hpp
index 891d1361ed..3f620e3d42 100755
--- a/vm/data_heap.hpp
+++ b/vm/data_heap.hpp
@@ -9,13 +9,10 @@ struct data_heap {
 	segment *seg;
 
 	zone *nursery;
-	zone *aging;
-	zone *aging_semispace;
-	zone *tenured;
-	zone *tenured_semispace;
-
-	char *allot_markers;
-	char *allot_markers_end;
+	old_space *aging;
+	old_space *aging_semispace;
+	old_space *tenured;
+	old_space *tenured_semispace;
 
 	char *cards;
 	char *cards_end;
diff --git a/vm/image.cpp b/vm/image.cpp
index 9a70937508..272309063b 100755
--- a/vm/image.cpp
+++ b/vm/image.cpp
@@ -280,7 +280,7 @@ void factor_vm::relocate_data()
 		relocating += untagged_object_size((object *)relocating))
 	{
 		object *obj = (object *)relocating;
-		allot_barrier(obj);
+		data->tenured->record_allocation(obj);
 		relocate_object(obj);
 	}
 }
diff --git a/vm/local_roots.cpp b/vm/local_roots.cpp
deleted file mode 100644
index 71baee6deb..0000000000
--- a/vm/local_roots.cpp
+++ /dev/null
@@ -1,5 +0,0 @@
-#include "master.hpp"
-
-namespace factor
-{
-}
diff --git a/vm/master.hpp b/vm/master.hpp
index d942c1a3ac..97e9ed4a8b 100755
--- a/vm/master.hpp
+++ b/vm/master.hpp
@@ -69,9 +69,10 @@ namespace factor
 #include "bignumint.hpp"
 #include "bignum.hpp"
 #include "code_block.hpp"
-#include "gc/zone.hpp"
-#include "data_heap.hpp"
+#include "zone.hpp"
 #include "write_barrier.hpp"
+#include "old_space.hpp"
+#include "data_heap.hpp"
 #include "data_gc.hpp"
 #include "debug.hpp"
 #include "strings.hpp"
diff --git a/vm/old_space.hpp b/vm/old_space.hpp
new file mode 100644
index 0000000000..598c1f4090
--- /dev/null
+++ b/vm/old_space.hpp
@@ -0,0 +1,62 @@
+namespace factor
+{
+
+struct old_space : zone {
+	card *allot_markers;
+	card *allot_markers_end;
+
+	old_space(cell size_, cell start_) : zone(size_,start_)
+	{
+		cell cards_size = size_ >> card_bits;
+		allot_markers = new card[cards_size];
+		allot_markers_end = allot_markers + cards_size;
+	}
+
+	~old_space()
+	{
+		delete[] allot_markers;
+	}
+
+	card *addr_to_allot_marker(object *a)
+	{
+		return (card *)((((cell)a - start) >> card_bits) + (cell)allot_markers);
+	}
+
+	/* we need to remember the first object allocated in the card */
+	void record_allocation(object *obj)
+	{
+		card *ptr = addr_to_allot_marker(obj);
+		if(*ptr == invalid_allot_marker)
+			*ptr = ((cell)obj & addr_card_mask);
+	}
+
+	cell card_offset(cell address)
+	{
+		return allot_markers[(address - start) >> card_bits];
+	}
+
+	object *allot(cell size)
+	{
+		if(here + size > end) return NULL;
+
+		object *obj = zone::allot(size);
+		record_allocation(obj);
+		return obj;
+	}
+
+	void clear_allot_markers()
+	{
+		memset(allot_markers,invalid_allot_marker,size >> card_bits);
+	}
+
+	/* object *next_object_after(object *ptr)
+	{
+		cell size = untagged_object_size(ptr);
+		if((cell)ptr + size < end)
+			return (object *)((cell)ptr + size);
+		else
+			return NULL;
+	} */
+};
+
+}
diff --git a/vm/vm.cpp b/vm/vm.cpp
index 15df6cc18a..50dc441086 100755
--- a/vm/vm.cpp
+++ b/vm/vm.cpp
@@ -4,6 +4,7 @@ namespace factor
 {
 
 factor_vm::factor_vm() :
+	nursery(0,0),
 	profiling_p(false),
 	secure_gc(false),
 	gc_off(false),
diff --git a/vm/vm.hpp b/vm/vm.hpp
index 9836342fe2..02ab128969 100755
--- a/vm/vm.hpp
+++ b/vm/vm.hpp
@@ -53,9 +53,6 @@ struct factor_vm
 	/* Code heap */
 	code_heap *code;
 
-	/* Where we store object start offsets in cards */
-	cell allot_markers_offset;
-
 	/* Only set if we're performing a GC */
 	gc_state *current_gc;
 
@@ -211,10 +208,9 @@ struct factor_vm
 	//data_heap
 	void init_card_decks();
 	data_heap *grow_data_heap(data_heap *data, cell requested_bytes);
-	void clear_cards(zone *gen);
-	void clear_decks(zone *gen);
-	void clear_allot_markers(zone *gen);
-	void reset_generation(zone *gen);
+	void clear_cards(old_space *gen);
+	void clear_decks(old_space *gen);
+	void reset_generation(old_space *gen);
 	void set_data_heap(data_heap *data_);
 	void init_data_heap(cell young_size, cell aging_size, cell tenured_size, bool secure_gc_);
 	cell untagged_object_size(object *pointer);
@@ -243,11 +239,6 @@ struct factor_vm
 		return ((cell)c - cards_offset) << card_bits;
 	}
 
-	inline cell card_offset(card *c)
-	{
-		return *(c - (cell)data->cards + (cell)data->allot_markers);
-	}
-
 	inline card_deck *addr_to_deck(cell a)
 	{
 		return (card_deck *)(((cell)a >> deck_bits) + decks_offset);
@@ -263,11 +254,6 @@ struct factor_vm
 		return (card *)((((cell)d - decks_offset) << (deck_bits - card_bits)) + cards_offset);
 	}
 
-	inline card *addr_to_allot_marker(object *a)
-	{
-		return (card *)(((cell)a >> card_bits) + allot_markers_offset);
-	}
-
 	/* the write barrier must be called any time we are potentially storing a
 	   pointer from an older generation to a younger one */
 	inline void write_barrier(object *obj)
@@ -276,22 +262,14 @@ struct factor_vm
 		*addr_to_deck((cell)obj) = card_mark_mask;
 	}
 
-	/* we need to remember the first object allocated in the card */
-	inline void allot_barrier(object *address)
-	{
-		card *ptr = addr_to_allot_marker(address);
-		if(*ptr == invalid_allot_marker)
-			*ptr = ((cell)address & addr_card_mask);
-	}
-
 	// data_gc
 	template<typename Strategy> object *resolve_forwarding(object *untagged, Strategy &strategy);
 	template<typename Strategy> void trace_handle(cell *handle, Strategy &strategy);
 	template<typename Strategy> object *promote_object(object *pointer, Strategy &strategy);
 	template<typename Strategy> void trace_slots(object *ptr, Strategy &strategy);
-	template<typename Strategy> void trace_card(card *ptr, cell here, Strategy &strategy);
-	template<typename Strategy> void trace_card_deck(card_deck *deck, cell here, card mask, card unmask, Strategy &strategy);
-	template<typename Strategy> void trace_cards(cell gen, zone *z, Strategy &strategy);
+	template<typename Strategy> void trace_card(card *ptr, old_space *gen, Strategy &strategy);
+	template<typename Strategy> void trace_card_deck(card_deck *deck, old_space *gen, card mask, card unmask, Strategy &strategy);
+	template<typename Strategy> void trace_cards(cell gen, old_space *z, Strategy &strategy);
 	template<typename Strategy> void trace_stack_elements(segment *region, cell top, Strategy &strategy);
 	template<typename Strategy> void trace_registered_locals(Strategy &strategy);
 	template<typename Strategy> void trace_registered_bignums(Strategy &strategy);
diff --git a/vm/write_barrier.cpp b/vm/write_barrier.cpp
deleted file mode 100644
index 774f744a3f..0000000000
--- a/vm/write_barrier.cpp
+++ /dev/null
@@ -1,4 +0,0 @@
-#include "master.hpp"
-
-using namespace factor;
-
diff --git a/vm/gc/zone.hpp b/vm/zone.hpp
similarity index 100%
rename from vm/gc/zone.hpp
rename to vm/zone.hpp