diff --git a/autotest.c b/autotest.c
index 8f34602..d7e7e3b 100644
--- a/autotest.c
+++ b/autotest.c
@@ -107,7 +107,7 @@ int main(int argc, char** argv)
 {
 	struct fpga_model model;
 	struct fpga_device* P46_dev, *P48_dev, *logic_dev;
-	int P46_y, P46_x, P46_idx, P48_y, P48_x, P48_idx, rc;
+	int P46_y, P46_x, P46_idx, P48_y, P48_x, P48_idx, dev_idx, rc;
 	struct test_state tstate;
 	struct switch_to_yx switch_to;
 
@@ -137,8 +137,9 @@ int main(int argc, char** argv)
 	// configure P46
 	rc = fpga_find_iob(&model, "P46", &P46_y, &P46_x, &P46_idx);
 	if (rc) FAIL(rc);
-	P46_dev = fpga_dev(&model, P46_y, P46_x, DEV_IOB, P46_idx);
-	if (!P46_dev) FAIL(EINVAL);
+	dev_idx = fpga_dev_idx(&model, P46_y, P46_x, DEV_IOB, P46_idx);
+	if (dev_idx == NO_DEV) FAIL(EINVAL);
+	P46_dev = FPGA_DEV(&model, P46_y, P46_x, dev_idx);
 	P46_dev->instantiated = 1;
 	strcpy(P46_dev->iob.istandard, IO_LVCMOS33);
 	P46_dev->iob.bypass_mux = BYPASS_MUX_I;
@@ -147,8 +148,9 @@ int main(int argc, char** argv)
 	// configure P48
 	rc = fpga_find_iob(&model, "P48", &P48_y, &P48_x, &P48_idx);
 	if (rc) FAIL(rc);
-	P48_dev = fpga_dev(&model, P48_y, P48_x, DEV_IOB, P48_idx);
-	if (!P48_dev) FAIL(EINVAL);
+	dev_idx = fpga_dev_idx(&model, P48_y, P48_x, DEV_IOB, P48_idx);
+	if (dev_idx == NO_DEV) FAIL(EINVAL);
+	P48_dev = FPGA_DEV(&model, P48_y, P48_x, dev_idx);
 	P48_dev->instantiated = 1;
 	strcpy(P48_dev->iob.ostandard, IO_LVCMOS33);
 	P48_dev->iob.drive_strength = 12;
@@ -157,8 +159,9 @@ int main(int argc, char** argv)
 	P48_dev->iob.suspend = SUSP_3STATE;
 
 	// configure logic
-	logic_dev = fpga_dev(&model, /*y*/ 68, /*x*/ 13, DEV_LOGIC, DEV_LOGX);
-	if (!logic_dev) FAIL(EINVAL);
+	dev_idx = fpga_dev_idx(&model, /*y*/ 68, /*x*/ 13, DEV_LOGIC, DEV_LOGX);
+	if (dev_idx == NO_DEV) FAIL(EINVAL);
+	logic_dev = FPGA_DEV(&model, /*y*/ 68, /*x*/ 13, dev_idx);
 	logic_dev->instantiated = 1;
 	logic_dev->logic.D_used = 1;
 	rc = fpga_set_lut(&model, logic_dev, D6_LUT, "A3", ZTERM);
diff --git a/bit_frames.c b/bit_frames.c
index 279b38d..706a0d5 100644
--- a/bit_frames.c
+++ b/bit_frames.c
@@ -75,7 +75,7 @@ static struct bit_pos s_default_bits[] = {
 
 int extract_model(struct fpga_model* model, struct fpga_bits* bits)
 {
-	int i, num_iobs, iob_y, iob_x, iob_idx, row, row_pos, rc;
+	int i, num_iobs, iob_y, iob_x, iob_idx, dev_idx, row, row_pos, rc;
 	int x, y, byte_off;
 	uint32_t* u32_p;
 	uint8_t* u8_p;
@@ -102,8 +102,9 @@ int extract_model(struct fpga_model* model, struct fpga_bits* bits)
 		}
 		rc = fpga_find_iob(model, iob_sitename, &iob_y, &iob_x, &iob_idx);
 		if (rc) FAIL(rc);
-		dev = fpga_dev(model, iob_y, iob_x, DEV_IOB, iob_idx);
-		if (!dev) FAIL(rc);
+		dev_idx = fpga_dev_idx(model, iob_y, iob_x, DEV_IOB, iob_idx);
+		if (dev_idx == NO_DEV) FAIL(EINVAL);
+		dev = FPGA_DEV(model, iob_y, iob_x, dev_idx);
 
 		// we only support 2 hardcoded types of IOB right now
 		// todo: bit 7 goes on when out-net connected?
@@ -173,8 +174,9 @@ int extract_model(struct fpga_model* model, struct fpga_bits* bits)
 				clear_bit(bits, /*row*/ 0, /*major*/ 17,
 					/*minor*/ 22, /*bit_i*/ 980);
 
-				dev = fpga_dev(model, y, x, DEV_LOGIC, DEV_LOGX);
-				if (!dev) FAIL(EINVAL);
+				dev_idx = fpga_dev_idx(model, y, x, DEV_LOGIC, DEV_LOGX);
+				if (dev_idx == NO_DEV) FAIL(EINVAL);
+				dev = FPGA_DEV(model, y, x, dev_idx);
 				dev->instantiated = 1;
 				*(uint64_t*)(u8_p+26*FRAME_SIZE+byte_off) = 0;
 
diff --git a/control.c b/control.c
index 5c330df..31b6133 100644
--- a/control.c
+++ b/control.c
@@ -200,34 +200,35 @@ const char* fpga_iob_sitename(struct fpga_model* model, int y, int x,
 	return 0;
 }
 
-struct fpga_device* fpga_dev(struct fpga_model* model,
-	int y, int x, enum fpgadev_type type, int type_idx)
+dev_idx_t fpga_dev_idx(struct fpga_model* model,
+	int y, int x, enum fpgadev_type type, dev_type_idx_t type_idx)
 {
 	struct fpga_tile* tile;
-	int type_count, i;
+	dev_type_idx_t type_count;
+	dev_idx_t i;
 
 	tile = YX_TILE(model, y, x);
 	type_count = 0;
 	for (i = 0; i < tile->num_devs; i++) {
 		if (tile->devs[i].type == type) {
 			if (type_count == type_idx)
-				return &tile->devs[i];
+				return i;
 			type_count++;
 		}
 	}
-	return 0;
+	return NO_DEV;
 }
 
-int fpga_dev_typecount(struct fpga_model* model, int y, int x,
-	enum fpgadev_type type, int dev_idx)
+dev_type_idx_t fpga_dev_typeidx(struct fpga_model* model, int y, int x,
+	dev_idx_t dev_idx)
 {
 	struct fpga_tile* tile;
-	int type_count, i;
+	dev_type_idx_t type_count, i;
 
 	tile = YX_TILE(model, y, x);
 	type_count = 0;
 	for (i = 0; i < dev_idx; i++) {
-		if (tile->devs[i].type == type)
+		if (tile->devs[i].type == tile->devs[dev_idx].type)
 			type_count++;
 	}
 	return type_count;
@@ -749,3 +750,37 @@ int fpga_switch_to_yx(struct switch_to_yx* p)
 	}
 	return 0;
 }
+
+int fpga_net_new(struct fpga_model* model, net_idx_t* new_idx)
+{
+	return -1;
+}
+
+int fpga_net_enum(struct fpga_model* model, net_idx_t last, net_idx_t* next)
+{
+	*next = NO_NET;
+	return 0;
+}
+
+struct fpga_net* fpga_net_get(struct fpga_model* model, net_idx_t net_i)
+{
+	return 0;
+}
+
+int fpga_net_add_port(struct fpga_model* model, net_idx_t net_i,
+	int y, int x, dev_idx_t dev_idx, pinw_idx_t pinw_idx)
+{
+	return -1;
+}
+
+int fpga_net_add_switches(struct fpga_model* model, net_idx_t net_i,
+	const struct sw_set* set)
+{
+	return -1;
+}
+
+void fpga_net_free_all(struct fpga_model* model)
+{
+	free(model->nets);
+	model->nets = 0;
+}
diff --git a/control.h b/control.h
index 7776464..6ecb95b 100644
--- a/control.h
+++ b/control.h
@@ -17,14 +17,14 @@ const char* fpga_iob_sitename(struct fpga_model* model, int y, int x,
 // 2. The index of the device within devices of the same type in the tile.
 //
 
-// Looks up a device pointer based on the type index.
-struct fpga_device* fpga_dev(struct fpga_model* model,
-	int y, int x, enum fpgadev_type type, int type_idx);
+// Looks up a device index based on the type index.
+dev_idx_t fpga_dev_idx(struct fpga_model* model,
+	int y, int x, enum fpgadev_type type, dev_type_idx_t type_idx);
 
-// Counts how many devices of type 'type' are in the device
-// array up to devidx.
-int fpga_dev_typecount(struct fpga_model* model, int y, int x,
-	enum fpgadev_type type, int dev_idx);
+// Counts how many devices of the same type as dev_idx are in
+// the array up to dev_idx.
+dev_type_idx_t fpga_dev_typeidx(struct fpga_model* model, int y, int x,
+	dev_idx_t dev_idx);
 
 enum { A6_LUT, B6_LUT, C6_LUT, D6_LUT };
 // lut_len can be -1 (ZTERM)
@@ -41,6 +41,10 @@ int fpga_connpt_find(struct fpga_model* model, int y, int x,
 void fpga_conn_dest(struct fpga_model* model, int y, int x,
 	int connpt_dest_idx, int* dest_y, int* dest_x, str16_t* str_i);
 
+//
+// switches
+//
+
 typedef int swidx_t; // swidx_t is an index into the uint32_t switches array
 #define MAX_SW_DEPTH 64 // largest seen so far was 20
 
@@ -161,3 +165,47 @@ struct switch_to_yx
 };
 
 int fpga_switch_to_yx(struct switch_to_yx* p);
+
+//
+// nets
+//
+
+// The last m1 soc has about 20k nets with about 470k
+// connection points. The largest net has about 110
+// connection points. For now we work with a simple
+// fixed-size array, we can later make this more dynamic
+// depending on which load on the memory manager is better.
+#define MAX_NET_SIZE	128
+
+#define NET_IDX_IS_PINW	0x8000
+#define NET_IDX_MASK	0x7FFF
+
+struct net_el
+{
+	uint16_t y;
+	uint16_t x;
+	// idx is either an index into tile->switches[]
+	// if bit15 (NET_IDX_IS_PINW) is off, or an index
+	// into dev->pinw[] if bit15 is on.
+	uint16_t idx;
+	uint16_t dev_idx; // only used if idx&NET_IDX_IS_PINW
+};
+
+struct fpga_net
+{
+	int size;
+	struct net_el el[MAX_NET_SIZE];
+};
+
+typedef int net_idx_t;
+#define NO_NET 0
+
+int fpga_net_new(struct fpga_model* model, net_idx_t* new_idx);
+// start a new enumeration by calling with last==NO_NET
+int fpga_net_enum(struct fpga_model* model, net_idx_t last, net_idx_t* next);
+struct fpga_net* fpga_net_get(struct fpga_model* model, net_idx_t net_i);
+int fpga_net_add_port(struct fpga_model* model, net_idx_t net_i,
+	int y, int x, dev_idx_t dev_idx, pinw_idx_t pinw_idx);
+int fpga_net_add_switches(struct fpga_model* model, net_idx_t net_i,
+	const struct sw_set* set);
+void fpga_net_free_all(struct fpga_model* model);
diff --git a/floorplan.c b/floorplan.c
index 714a373..b8df162 100644
--- a/floorplan.c
+++ b/floorplan.c
@@ -772,7 +772,7 @@ static void read_dev_line(struct fpga_model* model, const char* line, int start)
 	int coord_end, y_coord, x_coord;
 	int type_beg, type_end, idx_beg, idx_end;
 	enum fpgadev_type dev_type;
-	int dev_idx, words_consumed;
+	int dev_type_idx, dev_idx, words_consumed;
 	struct fpga_device* dev_ptr;
 	int next_beg, next_end, second_beg, second_end;
 
@@ -788,12 +788,13 @@ static void read_dev_line(struct fpga_model* model, const char* line, int start)
 		return;
 	}
 	dev_type = to_type(&line[type_beg], type_end-type_beg);
-	dev_idx = to_i(&line[idx_beg], idx_end-idx_beg);
-	dev_ptr = fpga_dev(model, y_coord, x_coord, dev_type, dev_idx);
-	if (!dev_ptr) {
+	dev_type_idx = to_i(&line[idx_beg], idx_end-idx_beg);
+	dev_idx = fpga_dev_idx(model, y_coord, x_coord, dev_type, dev_type_idx);
+	if (dev_idx == NO_DEV) {
 		fprintf(stderr, "error %i: %s", __LINE__, line);
 		return;
 	}
+	dev_ptr = FPGA_DEV(model, y_coord, x_coord, dev_idx);
 
 	next_end = idx_end;
 	while (next_word(line, next_end, &next_beg, &next_end),
diff --git a/model.h b/model.h
index 9e4c85b..afd1fb7 100644
--- a/model.h
+++ b/model.h
@@ -75,6 +75,8 @@ struct fpga_model
 	struct fpga_tile* tiles;
 	struct hashed_strarray str;
 
+	struct fpga_net* nets;
+
 	// tmp_str will be allocated to hold max(x_width, y_height)
 	// pointers, useful for string seeding when running wires.
 	const char** tmp_str;
@@ -331,6 +333,21 @@ enum fpgadev_type
 	DEV_SPI_ACCESS
 };
 
+// We use two types of device indices, one is a flat index
+// into the tile->devs array (dev_idx_t), the other
+// one counts up from 0 through devices of one particular
+// type in the tile. The first logic device has type_idx == 0,
+// the second logic device has type_idx == 1, etc, no matter
+// at which index they are in the device array. The type indices
+// are used in the floorplan, the flat array indices internally
+// in memory.
+
+typedef int dev_idx_t;
+typedef int dev_type_idx_t;
+
+#define NO_DEV -1
+#define FPGA_DEV(model, y, x, dev_idx)	(&YX_TILE(model, y, x)->devs[dev_idx])
+
 // M and L device is always at type index 0, X device
 // is always at type index 1.
 #define DEV_LOGM 0
diff --git a/model_devices.c b/model_devices.c
index 00f9930..a202fe1 100644
--- a/model_devices.c
+++ b/model_devices.c
@@ -424,7 +424,7 @@ static int init_iob(struct fpga_model* model, int y, int x,
 
 	tile = YX_TILE(model, y, x);
 	tile->devs[idx].iob.subtype = subtype;
-	type_idx = fpga_dev_typecount(model, y, x, DEV_IOB, idx);
+	type_idx = fpga_dev_typeidx(model, y, x, idx);
 	if (!y)
 		prefix = "TIOB";
 	else if (y == model->y_height - BOT_OUTER_ROW)