diff --git a/fuzzers/005-tilegrid/generate_full.py b/fuzzers/005-tilegrid/generate_full.py
index b75de807..4b5277c5 100644
--- a/fuzzers/005-tilegrid/generate_full.py
+++ b/fuzzers/005-tilegrid/generate_full.py
@@ -215,7 +215,7 @@ def propagate_rebuf(database, tiles_by_grid):
     """ Writing a fuzzer for the CLK_BUFG_REBUF tiles is hard, so propigate from CLK_HROW tiles.
 
     In the clock column, there is a CLK_BUFG_REBUF above and below the CLK_HROW
-    tile.  Each clock column appears to use the same offsets, so propigdate
+    tile.  Each clock column appears to use the same offsets, so propigate
     the base address and frame count, and update the offset and word count.
 
     """
diff --git a/fuzzers/041-clk-hrow-pips/Makefile b/fuzzers/041-clk-hrow-pips/Makefile
index 1bb8bc01..155094ec 100644
--- a/fuzzers/041-clk-hrow-pips/Makefile
+++ b/fuzzers/041-clk-hrow-pips/Makefile
@@ -5,7 +5,7 @@ MAKETODO_FLAGS=--no-l --pip-type clk_hrow_bot --seg-type clk_hrow_bot --re "[^\.
 N = 50
 
 # These PIPs all appear to be either a 0 or 2 bit solution.
-SEGMATCH_FLAGS=-m 20 -M 45 -c 2
+SEGMATCH_FLAGS=-m 20 -M 45 -c 1
 SPECIMENS_DEPS=build/cmt_regions.csv
 A_PIPLIST=clk_hrow_bot_r.txt
 
@@ -18,7 +18,7 @@ build/cmt_regions.csv: output_cmt.tcl
 	cd build/ && ${XRAY_VIVADO} -mode batch -source ${FUZDIR}/output_cmt.tcl
 
 build/segbits_clk_hrow.rdb: $(SPECIMENS_OK)
-	${XRAY_SEGMATCH} -o build/segbits_clk_hrow.rdb \
+	${XRAY_SEGMATCH} ${SEGMATCH_FLAGS} -o build/segbits_clk_hrow.rdb \
 		$(addsuffix /segdata_clk_hrow_top_r.txt,$(SPECIMENS)) \
 		$(addsuffix /segdata_clk_hrow_bot_r.txt,$(SPECIMENS))
 
diff --git a/fuzzers/041-clk-hrow-pips/generate.py b/fuzzers/041-clk-hrow-pips/generate.py
index fe4e53c0..f9b20ba2 100644
--- a/fuzzers/041-clk-hrow-pips/generate.py
+++ b/fuzzers/041-clk-hrow-pips/generate.py
@@ -9,6 +9,9 @@ def main():
     table = clk_table.get_clk_table()
 
     print("Loading tags from design.txt.")
+
+    active_gclks = {}
+    active_clks = {}
     with open("design.txt", "r") as f:
         for line in f:
             tile, pip, src, dst, pnum, pdir = line.split()
@@ -44,6 +47,30 @@ def main():
                     segmk.add_tile_tag(
                         tile, '{}.HCLK_ENABLE_COLUMN{}'.format(dst, column), 0)
 
+                if tile not in active_clks:
+                    active_clks[tile] = set()
+
+                active_clks[tile].add(src)
+
+                if 'GCLK' in src:
+                    if src not in active_gclks:
+                        active_gclks[src] = set()
+
+                    active_gclks[src].add(tile)
+
+    tiles = sorted(active_clks.keys())
+
+    for tile in active_clks:
+        for src in table:
+            if 'GCLK' not in src:
+                active = src in active_clks[tile]
+                segmk.add_tile_tag(tile, '{}_ACTIVE'.format(src), active)
+            else:
+                if src not in active_gclks:
+                    segmk.add_tile_tag(tile, '{}_ACTIVE'.format(src), 0)
+                elif tile in active_gclks[src]:
+                    segmk.add_tile_tag(tile, '{}_ACTIVE'.format(src), 1)
+
     segmk.compile()
     segmk.write()
 
diff --git a/fuzzers/041-clk-hrow-pips/merge_clk_entries.py b/fuzzers/041-clk-hrow-pips/merge_clk_entries.py
index f7e2ea27..1ddd2ebe 100644
--- a/fuzzers/041-clk-hrow-pips/merge_clk_entries.py
+++ b/fuzzers/041-clk-hrow-pips/merge_clk_entries.py
@@ -11,6 +11,7 @@ def main():
 
     args = parser.parse_args()
 
+    output_features = []
     hrow_outs = {}
     tile = None
     with open(args.in_segbit) as f:
@@ -19,6 +20,11 @@ def main():
             feature = parts[0]
             bits = ' '.join(parts[1:])
 
+            # No post-processing on _ACTIVE bits.
+            if feature.endswith('_ACTIVE'):
+                output_features.append(l.strip())
+                continue
+
             tile1, dst, src = feature.split('.')
             if tile is None:
                 tile = tile1
@@ -53,6 +59,9 @@ def main():
     table = clk_table.get_clk_table()
 
     with open(args.out_segbit, 'w') as f:
+        for l in output_features:
+            print(l, file=f)
+
         for dst in sorted(hrow_outs):
             for src in sorted(piplists[dst]):
                 if src not in table: