diff --git a/Makefile b/Makefile
index 4ea0328c..2f9e806f 100644
--- a/Makefile
+++ b/Makefile
@@ -50,7 +50,7 @@ CFLAGS += -Ilib -Idep/fmt -Iarch
 export OBJDIR = .obj
 
 all: .obj/build.ninja
-	@ninja -f .obj/build.ninja
+	@ninja -f .obj/build.ninja -v
 	@if command -v cscope > /dev/null; then cscope -bRq; fi
 
 clean:
diff --git a/arch/ibm/encoder.cc b/arch/ibm/encoder.cc
index 55e63947..fef40622 100644
--- a/arch/ibm/encoder.cc
+++ b/arch/ibm/encoder.cc
@@ -115,6 +115,8 @@ public:
 		IbmEncoderProto::TrackdataProto trackdata;
 		getTrackFormat(trackdata, physicalTrack, physicalSide);
 
+		if (trackdata.swap_sides())
+			physicalSide = 1 - physicalSide;
 		for (char sectorChar : trackdata.sector_skew())
         {
 			int sectorId = charToInt(sectorChar);
diff --git a/mkninja.sh b/mkninja.sh
index 2470e77f..026dcdde 100644
--- a/mkninja.sh
+++ b/mkninja.sh
@@ -35,6 +35,10 @@ rule test
     command = \$in && touch \$out
     description = TEST \$in
 
+rule encodedecode
+    command = sh scripts/encodedecodetest.sh \$format > \$out
+    description = ENCODEDECODE \$format
+
 rule strip
     command = cp -f \$in \$out && $STRIP \$out
     description = STRIP \$in
@@ -255,6 +259,14 @@ runtest() {
     echo build $OBJDIR/$prog.stamp : test $OBJDIR/$prog-debug$EXTENSION
 }
 
+encodedecodetest() {
+    local format
+    format=$1
+
+    echo "build $OBJDIR/$format.encodedecode.stamp : encodedecode | fluxengine scripts/encodedecodetest.sh"
+    echo "    format=$format"
+}
+
 buildlibrary libagg.a \
     -Idep/agg/include \
     dep/stb/stb_image_write.c \
@@ -374,13 +386,8 @@ buildlibrary libbackend.a \
     lib/utils.cc \
     lib/writer.cc \
 
-FORMATS="\
-    acornadfs \
-    acorndfs \
-    aeslanier \
+RWFORMATS="\
     amiga \
-    ampro \
-    apple2 \
     atarist360 \
     atarist370 \
     atarist400 \
@@ -393,41 +400,49 @@ FORMATS="\
     brother240 \
     commodore1541 \
     commodore1581 \
-    eco1 \
-    f85 \
-    fb100 \
-    hplif770 \
-    ibm \
     ibm1200_525 \
     ibm1440 \
     ibm180_525 \
     ibm360_525 \
     ibm720 \
     ibm720_525 \
-    mac400 \
     mac800 \
-    micropolis \
-    mx \
     northstar87 \
     northstar175 \
     northstar350 \
     tids990 \
+    "
+
+ROFORMATS="\
+    acornadfs \
+    acorndfs \
+    aeslanier \
+    ampro \
+    apple2 \
+    eco1 \
+    f85 \
+    fb100 \
+    hplif770 \
+    ibm \
+    mac400 \
+    micropolis \
+    mx \
     victor9k \
     zilogmcz \
     "
 
-for pb in $FORMATS; do
+for pb in $RWFORMATS $ROFORMATS; do
     buildencodedproto $OBJDIR/proto/libconfig.def ConfigProto \
         formats_${pb}_pb src/formats/$pb.textpb $OBJDIR/proto/src/formats/$pb.cc
 done
 
-buildmktable formats $OBJDIR/formats.cc $FORMATS
+buildmktable formats $OBJDIR/formats.cc $RWFORMATS $ROFORMATS
 
 buildlibrary libfrontend.a \
     -I$OBJDIR/proto \
     -d $OBJDIR/proto/libconfig.def \
     -d $OBJDIR/proto/libdata.def \
-    $(for a in $FORMATS; do echo $OBJDIR/proto/src/formats/$a.cc; done) \
+    $(for a in $RWFORMATS $ROFORMATS; do echo $OBJDIR/proto/src/formats/$a.cc; done) \
     $OBJDIR/formats.cc \
     src/fe-analysedriveresponse.cc \
     src/fe-analyselayout.cc \
@@ -492,5 +507,9 @@ runtest proto-test          -I$OBJDIR/proto \
                             tests/proto.cc \
                             $OBJDIR/proto/tests/testproto.cc
 
+for f in $RWFORMATS; do
+    encodedecodetest $f
+done
+
 # vim: sw=4 ts=4 et
 
diff --git a/scripts/encodedecodetest.sh b/scripts/encodedecodetest.sh
index 4e88bb45..97fecbba 100755
--- a/scripts/encodedecodetest.sh
+++ b/scripts/encodedecodetest.sh
@@ -8,18 +8,18 @@ format=$1
 
 trap "rm -f $srcfile $fluxfile $destfile" EXIT
 
-dd if=/dev/urandom of=$srcfile bs=1M count=2
+dd if=/dev/urandom of=$srcfile bs=1M count=2 2>1
 
 ./fluxengine write $format -i $srcfile -d $fluxfile
 ./fluxengine read $format -s $fluxfile -o $destfile
 if [ ! -s $destfile ]; then
-	echo "Zero length output file!"
+	echo "Zero length output file!" >&2
 	exit 1
 fi
 
 truncate $srcfile -r $destfile
 if ! cmp $srcfile $destfile; then
-	echo "Comparison failed!"
+	echo "Comparison failed!" >&2
 	exit 1
 fi
 exit 0