diff --git a/fuzzers/025-bram-config/Makefile b/fuzzers/025-bram-config/Makefile
index bfbe7b23..0fb57ca7 100644
--- a/fuzzers/025-bram-config/Makefile
+++ b/fuzzers/025-bram-config/Makefile
@@ -1,19 +1,2 @@
-# read/write width is relatively slow to resolve
-# Even slower with multi bit masks...
-N := 8
-include ../fuzzer.mk
-
-database: build/segbits_bramx.db
-
-build/segbits_bramx.rdb: $(SPECIMENS_OK)
-	${XRAY_SEGMATCH} -o build/segbits_bramx.rdb $(addsuffix /segdata_bram_[lr].txt,$(SPECIMENS))
-
-build/segbits_bramx.db: build/segbits_bramx.rdb
-	${XRAY_DBFIXUP} --db-root build --zero-db bits.dbf --seg-fn-in $^ --seg-fn-out $@
-
-pushdb:
-	${XRAY_MERGEDB} bram_l build/segbits_bramx.db
-	${XRAY_MERGEDB} bram_r build/segbits_bramx.db
-
-.PHONY: database pushdb
-
+N ?= 8
+include ../bram.mk
diff --git a/fuzzers/026-bram-data/Makefile b/fuzzers/026-bram-data/Makefile
index 0eb8fdb1..0fb57ca7 100644
--- a/fuzzers/026-bram-data/Makefile
+++ b/fuzzers/026-bram-data/Makefile
@@ -1,29 +1,2 @@
-N := 8
-SPECIMENS := $(addprefix build/specimen_,$(shell seq -f '%03.0f' $(N)))
-SPECIMENS_OK := $(addsuffix /OK,$(SPECIMENS))
-
-database: $(SPECIMENS_OK)
-	${XRAY_SEGMATCH} -o build/segbits_bramx.block_ram.db $(addsuffix /segdata_bram_[lr].txt,$(SPECIMENS))
-
-pushdb:
-	${XRAY_MERGEDB} bram_l.block_ram build/segbits_bramx.block_ram.db
-	${XRAY_MERGEDB} bram_r.block_ram build/segbits_bramx.block_ram.db
-
-build:
-	mkdir build
-
-$(SPECIMENS_OK): build
-	bash generate.sh $(subst /OK,,$@)
-	touch $@
-
-run:
-	$(MAKE) clean
-	$(MAKE) database
-	$(MAKE) pushdb
-	touch run.ok
-
-clean:
-	rm -rf build
-
-.PHONY: database pushdb clean
-
+N ?= 8
+include ../bram.mk
diff --git a/fuzzers/030-iob/Makefile b/fuzzers/030-iob/Makefile
index 24e5cfd1..6cb898c1 100644
--- a/fuzzers/030-iob/Makefile
+++ b/fuzzers/030-iob/Makefile
@@ -1,16 +1,20 @@
 N := 1
 include ../fuzzer.mk
 
+SEGDATAS=$(addsuffix /segdata_liob33.txt,$(SPECIMENS))
+
 database: build/segbits_liob33.db
 
 build/segbits_liob33.rdb:
-	${XRAY_SEGMATCH} -o build/segbits_liob33.rdb $(addsuffix /segdata_liob33.txt,$(SPECIMENS))
+	${XRAY_SEGMATCH} -o build/segbits_liob33.rdb $(SEGDATAS)
 
 build/segbits_liob33.db: build/segbits_liob33.rdb
 	${XRAY_DBFIXUP} --db-root build --zero-db bits.dbf --seg-fn-in $^ --seg-fn-out $@
+	${XRAY_MASKMERGE} build/mask_liob33.db $(SEGDATAS)
 
 pushdb:
 	${XRAY_MERGEDB} liob33 build/segbits_liob33.db
+	${XRAY_MERGEDB} mask_liob33 build/mask_liob33.db
 
 .PHONY: database pushdb
 
diff --git a/fuzzers/031-mmcm/Makefile b/fuzzers/031-mmcm/Makefile
index bfbe7b23..9007ec88 100644
--- a/fuzzers/031-mmcm/Makefile
+++ b/fuzzers/031-mmcm/Makefile
@@ -3,17 +3,10 @@
 N := 8
 include ../fuzzer.mk
 
-database: build/segbits_bramx.db
-
-build/segbits_bramx.rdb: $(SPECIMENS_OK)
-	${XRAY_SEGMATCH} -o build/segbits_bramx.rdb $(addsuffix /segdata_bram_[lr].txt,$(SPECIMENS))
-
-build/segbits_bramx.db: build/segbits_bramx.rdb
-	${XRAY_DBFIXUP} --db-root build --zero-db bits.dbf --seg-fn-in $^ --seg-fn-out $@
+database: $(SPECIMENS_OK)
 
 pushdb:
-	${XRAY_MERGEDB} bram_l build/segbits_bramx.db
-	${XRAY_MERGEDB} bram_r build/segbits_bramx.db
+	echo "FIXME" && false
 
 .PHONY: database pushdb
 
diff --git a/fuzzers/032-pll/Makefile b/fuzzers/032-pll/Makefile
index bfbe7b23..9007ec88 100644
--- a/fuzzers/032-pll/Makefile
+++ b/fuzzers/032-pll/Makefile
@@ -3,17 +3,10 @@
 N := 8
 include ../fuzzer.mk
 
-database: build/segbits_bramx.db
-
-build/segbits_bramx.rdb: $(SPECIMENS_OK)
-	${XRAY_SEGMATCH} -o build/segbits_bramx.rdb $(addsuffix /segdata_bram_[lr].txt,$(SPECIMENS))
-
-build/segbits_bramx.db: build/segbits_bramx.rdb
-	${XRAY_DBFIXUP} --db-root build --zero-db bits.dbf --seg-fn-in $^ --seg-fn-out $@
+database: $(SPECIMENS_OK)
 
 pushdb:
-	${XRAY_MERGEDB} bram_l build/segbits_bramx.db
-	${XRAY_MERGEDB} bram_r build/segbits_bramx.db
+	echo "FIXME" && false
 
 .PHONY: database pushdb
 
diff --git a/fuzzers/100-dsp-mskpat/Makefile b/fuzzers/100-dsp-mskpat/Makefile
index 588ecc38..18e10f77 100644
--- a/fuzzers/100-dsp-mskpat/Makefile
+++ b/fuzzers/100-dsp-mskpat/Makefile
@@ -7,10 +7,14 @@ database: $(SPECIMENS_OK)
 	${XRAY_SEGMATCH} -o build/segbits_dsp_l.db $(addsuffix /segdata_dsp_l_*.txt,$(SPECIMENS))
 	${XRAY_SEGMATCH} -o build/segbits_dsp_r.db $(addsuffix /segdata_dsp_r_*.txt,$(SPECIMENS))
 	${XRAY_DBFIXUP} --db-root build --clb-int
+	${XRAY_MASKMERGE} build/mask_dsp_l.db $(addsuffix /segdata_dsp_l_*.txt,$(SPECIMENS))
+	${XRAY_MASKMERGE} build/mask_dsp_r.db $(addsuffix /segdata_dsp_r_*.txt,$(SPECIMENS))
 
 pushdb:
 	${XRAY_MERGEDB} dsp_l build/segbits_dsp_l.db
 	${XRAY_MERGEDB} dsp_r build/segbits_dsp_r.db
+	${XRAY_MERGEDB} mask_dsp_l build/segbits_dsp_l.db
+	${XRAY_MERGEDB} mask_dsp_r build/segbits_dsp_r.db
 
 $(SPECIMENS_OK):
 	bash generate.sh $(subst /OK,,$@)
diff --git a/fuzzers/bram.mk b/fuzzers/bram.mk
new file mode 100644
index 00000000..7d916fe4
--- /dev/null
+++ b/fuzzers/bram.mk
@@ -0,0 +1,28 @@
+# read/write width is relatively slow to resolve
+# Even slower with multi bit masks...
+N ?= 8
+DO_DBFIXUP?=N
+
+include ../fuzzer.mk
+
+database: build/segbits_bramx.db
+
+build/segbits_bramx.rdb: $(SPECIMENS_OK)
+	${XRAY_SEGMATCH} -o build/segbits_bramx.rdb $(addsuffix /segdata_bram_[lr].txt,$(SPECIMENS))
+
+build/segbits_bramx.db: build/segbits_bramx.rdb
+ifeq ($(DO_DBFIXUP),Y)
+	${XRAY_DBFIXUP} --db-root build --zero-db bits.dbf --seg-fn-in $^ --seg-fn-out $@
+else
+	cp $^ $@
+endif
+	${XRAY_MASKMERGE} build/mask_bramx.db $(addsuffix /segdata_bram_[lr].txt,$(SPECIMENS))
+
+pushdb:
+	${XRAY_MERGEDB} bram_l build/segbits_bramx.db
+	${XRAY_MERGEDB} bram_r build/segbits_bramx.db
+	${XRAY_MERGEDB} mask_bram_l build/mask_bramx.db
+	${XRAY_MERGEDB} mask_bram_r build/mask_bramx.db
+
+.PHONY: database pushdb
+
diff --git a/fuzzers/clb.mk b/fuzzers/clb.mk
index 139a625b..08dbacb3 100644
--- a/fuzzers/clb.mk
+++ b/fuzzers/clb.mk
@@ -1,32 +1,42 @@
 N ?= 1
 CLB_DBFIXUP ?=
+# Fuzzer that can accept SLICEL data
+# ie set to N if only for SLICEM
 SLICEL ?= Y
 
 include ../fuzzer.mk
 
 database: build/segbits_clbx.db
 
-build/segbits_clbx.rdb: $(SPECIMENS_OK)
 ifeq ($(SLICEL),Y)
-	${XRAY_SEGMATCH} -o build/segbits_clbx.rdb $(addsuffix /segdata_clbl[lm]_[lr].txt,$(SPECIMENS))
+SEGDATAS=$(addsuffix /segdata_clbl[lm]_[lr].txt,$(SPECIMENS))
 else
-	${XRAY_SEGMATCH} -o build/segbits_clbx.rdb $(addsuffix /segdata_clblm_[lr].txt,$(SPECIMENS))
+SEGDATAS=$(addsuffix /segdata_clblm_[lr].txt,$(SPECIMENS))
 endif
 
+
+build/segbits_clbx.rdb: $(SPECIMENS_OK)
+	${XRAY_SEGMATCH} -o build/segbits_clbx.rdb $(SEGDATAS)
+
 build/segbits_clbx.db: build/segbits_clbx.rdb
 ifeq ($(CLB_DBFIXUP),Y)
 	${XRAY_DBFIXUP} --db-root build --zero-db bits.dbf --seg-fn-in $^ --seg-fn-out $@
 else
 	cp $^ $@
 endif
+	${XRAY_MASKMERGE} build/mask_clbx.db $(SEGDATAS)
 
 pushdb:
 ifeq ($(SLICEL),Y)
 	${XRAY_MERGEDB} clbll_l build/segbits_clbx.db
 	${XRAY_MERGEDB} clbll_r build/segbits_clbx.db
+	${XRAY_MERGEDB} mask_clbll_l build/mask_clbx.db
+	${XRAY_MERGEDB} mask_clbll_r build/mask_clbx.db
 endif
 	${XRAY_MERGEDB} clblm_l build/segbits_clbx.db
 	${XRAY_MERGEDB} clblm_r build/segbits_clbx.db
+	${XRAY_MERGEDB} mask_clblm_l build/mask_clbx.db
+	${XRAY_MERGEDB} mask_clblm_r build/mask_clbx.db
 
 .PHONY: database pushdb
 
diff --git a/fuzzers/int_loop.mk b/fuzzers/int_loop.mk
index e8ae2a3e..3fcaf3c6 100644
--- a/fuzzers/int_loop.mk
+++ b/fuzzers/int_loop.mk
@@ -27,6 +27,10 @@ export FUZDIR=$(shell pwd)
 database: $(SPECIMENS_OK)
 	${XRAY_SEGMATCH} $(SEGMATCH_FLAGS) -o build/segbits_int_l.db $(shell find build -name segdata_int_l.txt)
 	${XRAY_SEGMATCH} $(SEGMATCH_FLAGS) -o build/segbits_int_r.db $(shell find build -name segdata_int_r.txt)
+	${XRAY_MASKMERGE} build/mask_clbll_l.db $(shell find build -name segdata_int_l.txt)
+	${XRAY_MASKMERGE} build/mask_clbll_r.db $(shell find build -name segdata_int_r.txt)
+	${XRAY_MASKMERGE} build/mask_clblm_l.db $(shell find build -name segdata_int_l.txt)
+	${XRAY_MASKMERGE} build/mask_clblm_r.db $(shell find build -name segdata_int_r.txt)
 	# Keep a copy to track iter progress
 	# Also is pre-fixup, which drops and converts
 	cp build/segbits_int_l.db build/$(ITER)/segbits_int_l.db
@@ -39,6 +43,10 @@ endif
 pushdb:
 	${XRAY_MERGEDB} int_l build/segbits_int_l.db
 	${XRAY_MERGEDB} int_r build/segbits_int_r.db
+	${XRAY_MERGEDB} mask_clbll_l build/mask_clbll_l.db
+	${XRAY_MERGEDB} mask_clbll_r build/mask_clbll_r.db
+	${XRAY_MERGEDB} mask_clblm_l build/mask_clblm_l.db
+	${XRAY_MERGEDB} mask_clblm_r build/mask_clblm_r.db
 
 $(SPECIMENS_OK): build/todo.txt
 	mkdir -p build/$(ITER)