diff --git a/src/guest/gdrom/cdi.c b/src/guest/gdrom/cdi.c
index 5ed24431..604bf382 100644
--- a/src/guest/gdrom/cdi.c
+++ b/src/guest/gdrom/cdi.c
@@ -13,9 +13,9 @@ static const char *cdi_version_names[] = {
     "2", "3", "3.5",
 };
 
-static const int cdi_sectors[] = {2048, 2336, 2352};
+static const char *cdi_sector_modes[] = {"CDDA", "MODE1", "MODE2"};
 
-static const char *cdi_modes[] = {"CDDA", "MODE1", "MODE2"};
+static const int cdi_sector_sizes[] = {2048, 2336, 2352};
 
 static const uint8_t cdi_start_mark[] = {0, 0, 1, 0, 0, 0, 255, 255, 255, 255};
 
@@ -145,14 +145,14 @@ static int cdi_parse_track(struct disc *disc, uint32_t version,
   }
 
   /* parse track info */
-  uint32_t pregap_len, track_len, mode, lba, total_len, sector_type;
+  uint32_t pregap_len, track_len, sector_mode, lba, total_len, sector_type;
   fseek(fp, 2, SEEK_CUR);
   r = fread(&pregap_len, 4, 1, fp);
   CHECK_EQ(r, 1);
   r = fread(&track_len, 4, 1, fp);
   CHECK_EQ(r, 1);
   fseek(fp, 6, SEEK_CUR);
-  r = fread(&mode, 4, 1, fp);
+  r = fread(&sector_mode, 4, 1, fp);
   CHECK_EQ(r, 1);
   fseek(fp, 12, SEEK_CUR);
   r = fread(&lba, 4, 1, fp);
@@ -168,61 +168,28 @@ static int cdi_parse_track(struct disc *disc, uint32_t version,
     return 0;
   }
 
-  if (sector_type >= ARRAY_SIZE(cdi_sectors)) {
+  if (sector_type >= ARRAY_SIZE(cdi_sector_sizes)) {
     LOG_WARNING("cdi_parse unsupported sector type 0x%x", sector_type);
     return 0;
   }
 
-  int sector_size = cdi_sectors[sector_type];
+  int sector_size = cdi_sector_sizes[sector_type];
   int data_offset = *track_offset + pregap_len * sector_size;
 
+  if (!track_set_layout(track, sector_mode, sector_size)) {
+    LOG_WARNING("cdi_parse unsupported track layout mode=%d size=%d",
+                sector_mode, sector_size);
+    return 0;
+  }
+
   track->fad = pregap_len + lba;
   track->adr = 0;
-  track->ctrl = mode == 0 ? 0 : 4;
-  if (mode == 0 && sector_size == 2352) {
-    track->sector_fmt = GD_SECTOR_CDDA;
-    track->header_size = 0;
-    track->error_size = 0;
-    track->data_size = 2352;
-  } else if (mode == 1 && sector_size == 2352) {
-    track->sector_fmt = GD_SECTOR_M1;
-    /* skip sync, header */
-    track->header_size = 16;
-    track->error_size = 288;
-    track->data_size = 2048;
-  } else if (mode == 1 && sector_size == 2336) {
-    track->sector_fmt = GD_SECTOR_M1;
-    track->header_size = 0;
-    track->error_size = 288;
-    track->data_size = 2048;
-  } else if (mode == 2 && sector_size == 2352) {
-    /* assume form1 */
-    track->sector_fmt = GD_SECTOR_M2F1;
-    /* skip sync, header and subheader */
-    track->header_size = 24;
-    track->error_size = 280;
-    track->data_size = 2048;
-  } else if (mode == 2 && sector_size == 2336) {
-    /* assume form1 */
-    track->sector_fmt = GD_SECTOR_M2F1;
-    /* skip subheader */
-    track->header_size = 8;
-    track->error_size = 280;
-    track->data_size = 2048;
-  } else {
-    LOG_WARNING("cdi_parse unexpected sector format %d / size %d",
-                track->sector_fmt, track->sector_size);
-    return 0;
-  }
-  track->sector_size = sector_size;
+  track->ctrl = sector_mode == 0 ? 0 : 4;
   track->file_offset = data_offset - track->fad * track->sector_size;
 
-  /* sanity check the track layout */
-  CHECK_EQ(track->header_size + track->error_size + track->data_size,
-           track->sector_size);
-
   LOG_INFO("cdi_parse_track track=%d fad=%d off=%d mode=%s/%d", track->num,
-           track->fad, data_offset, cdi_modes[mode], track->sector_size);
+           track->fad, data_offset, cdi_sector_modes[sector_mode],
+           track->sector_size);
 
   *track_offset += total_len * sector_size;
   *leadout_fad = track->fad + track_len;
diff --git a/src/guest/gdrom/chd.c b/src/guest/gdrom/chd.c
index 44e4cdff..251effc5 100644
--- a/src/guest/gdrom/chd.c
+++ b/src/guest/gdrom/chd.c
@@ -139,12 +139,6 @@ static int chd_parse(struct disc *disc, const char *filename) {
     /* sanity checks */
     CHECK_EQ(tkid, chd->num_tracks + 1);
 
-    if (strcmp(type, "MODE1") && strcmp(type, "MODE1_RAW") &&
-        strcmp(type, "AUDIO")) {
-      LOG_WARNING("chd_parse track type %s unsupported", type);
-      return 0;
-    }
-
     if (strcmp(subtype, "NONE")) {
       LOG_WARNING("chd_parse track subtype %s unsupported", subtype);
       return 0;
@@ -155,29 +149,37 @@ static int chd_parse(struct disc *disc, const char *filename) {
       return 0;
     }
 
+    /* figure out sector type */
+    int sector_mode = 0;
+    int sector_size = 0;
+
+    if (!strcmp(type, "AUDIO")) {
+      sector_mode = 0;
+      sector_size = 2352;
+    } else if (!strcmp(type, "MODE1")) {
+      sector_mode = 1;
+      sector_size = 2336;
+    } else if (!strcmp(type, "MODE1_RAW")) {
+      sector_mode = 1;
+      sector_size = 2352;
+    } else {
+      LOG_WARNING("chd_parse unexpected mode %s", type);
+      return 0;
+    }
+
     /* add track */
     CHECK_LT(chd->num_tracks, ARRAY_SIZE(chd->tracks));
     struct track *track = &chd->tracks[chd->num_tracks++];
+
+    if (!track_set_layout(track, sector_mode, sector_size)) {
+      LOG_WARNING("chd_parse unsupported track layout mode=%d sector_size=%d",
+                  sector_mode, sector_size);
+      return 0;
+    }
+
     track->num = chd->num_tracks;
     track->fad = fad;
     track->ctrl = strcmp(type, "AUDIO") == 0 ? 0 : 4;
-    track->sector_fmt = !strcmp(type, "AUDIO") ? GD_SECTOR_CDDA : GD_SECTOR_M1;
-    track->sector_size = !strcmp(type, "MODE1") ? 2048 : 2352;
-    switch (track->sector_fmt) {
-      case GD_SECTOR_CDDA:
-        track->header_size = 0;
-        track->error_size = 0;
-        track->data_size = 2352;
-        break;
-      case GD_SECTOR_M1:
-        track->header_size = 16;
-        track->error_size = 280;
-        track->data_size = 2048;
-        break;
-      default:
-        LOG_WARNING("chd_parse unexpected sector format %d", track->sector_fmt);
-        return 0;
-    }
     track->file_offset = fad - cad;
 
     LOG_INFO("chd_parse '%s' track=%d fad=%d secsz=%d", tmp, track->num,
diff --git a/src/guest/gdrom/disc.c b/src/guest/gdrom/disc.c
index 89fd97f3..c4195c9f 100644
--- a/src/guest/gdrom/disc.c
+++ b/src/guest/gdrom/disc.c
@@ -63,6 +63,61 @@ static void disc_patch_sector(struct disc *disc, int fad, uint8_t *data) {
   }
 }
 
+int track_set_layout(struct track *track, int sector_mode, int sector_size) {
+  track->sector_size = sector_size;
+
+  if (sector_mode == 0 && sector_size == 2352) {
+    track->sector_fmt = GD_SECTOR_CDDA;
+    track->header_size = 0;
+    track->error_size = 0;
+    track->data_size = 2352;
+  } else if (sector_mode == 1 && sector_size == 2048) {
+    track->sector_fmt = GD_SECTOR_M1;
+    track->header_size = 0;
+    track->error_size = 0;
+    track->data_size = 2048;
+  } else if (sector_mode == 1 && sector_size == 2352) {
+    track->sector_fmt = GD_SECTOR_M1;
+    /* skip sync, header */
+    track->header_size = 16;
+    track->error_size = 288;
+    track->data_size = 2048;
+  } else if (sector_mode == 1 && sector_size == 2336) {
+    track->sector_fmt = GD_SECTOR_M1;
+    track->header_size = 0;
+    track->error_size = 288;
+    track->data_size = 2048;
+  } else if (sector_mode == 2 && sector_size == 2048) {
+    /* assume form1 */
+    track->sector_fmt = GD_SECTOR_M2F1;
+    track->header_size = 0;
+    track->error_size = 0;
+    track->data_size = 2048;
+  } else if (sector_mode == 2 && sector_size == 2352) {
+    /* assume form1 */
+    track->sector_fmt = GD_SECTOR_M2F1;
+    /* skip sync, header and subheader */
+    track->header_size = 24;
+    track->error_size = 280;
+    track->data_size = 2048;
+  } else if (sector_mode == 2 && sector_size == 2336) {
+    /* assume form1 */
+    track->sector_fmt = GD_SECTOR_M2F1;
+    /* skip subheader */
+    track->header_size = 8;
+    track->error_size = 280;
+    track->data_size = 2048;
+  } else {
+    return 0;
+  }
+
+  /* sanity check */
+  CHECK_EQ(track->header_size + track->error_size + track->data_size,
+           track->sector_size);
+
+  return 1;
+}
+
 int disc_read_bytes(struct disc *disc, int fad, int len, uint8_t *dst,
                     int dst_size) {
   CHECK_LE(len, dst_size);
diff --git a/src/guest/gdrom/disc.h b/src/guest/gdrom/disc.h
index 495d02a9..fef79348 100644
--- a/src/guest/gdrom/disc.h
+++ b/src/guest/gdrom/disc.h
@@ -36,7 +36,7 @@ struct track {
   int adr;
   /* type of track */
   int ctrl;
-  /* sector info */
+  /* sector layout */
   int sector_fmt;
   int sector_size;
   int header_size;
@@ -104,4 +104,6 @@ int disc_read_sectors(struct disc *disc, int fad, int num_sectors,
 int disc_read_bytes(struct disc *disc, int fad, int len, uint8_t *dst,
                     int dst_size);
 
+int track_set_layout(struct track *track, int sector_mode, int sector_size);
+
 #endif
diff --git a/src/guest/gdrom/gdi.c b/src/guest/gdrom/gdi.c
index 9ec252b2..017d5feb 100644
--- a/src/guest/gdrom/gdi.c
+++ b/src/guest/gdrom/gdi.c
@@ -145,21 +145,23 @@ static int gdi_parse(struct disc *disc, const char *filename) {
     /* add track */
     CHECK_LT(gdi->num_tracks, ARRAY_SIZE(gdi->tracks));
     struct track *track = &gdi->tracks[gdi->num_tracks++];
+
+    /* sanity check */
+    CHECK_EQ(num, gdi->num_tracks);
+
+    if (!track_set_layout(track, 1, sector_size)) {
+      LOG_WARNING("gdi_parse unsupported track layout sector_size=%d",
+                  sector_size);
+      return 0;
+    }
+
     track->num = gdi->num_tracks;
     track->fad = lba + GDROM_PREGAP;
     track->ctrl = ctrl;
-    track->sector_fmt = GD_SECTOR_M1;
-    track->sector_size = sector_size;
-    track->header_size = 16;
-    track->error_size = 288;
-    track->data_size = 2048;
     track->file_offset = file_offset - track->fad * track->sector_size;
     snprintf(track->filename, sizeof(track->filename), "%s" PATH_SEPARATOR "%s",
              dirname, filename);
 
-    /* sanity check */
-    CHECK_EQ(num, track->num);
-
     LOG_INFO("gdi_parse track=%d filename='%s' fad=%d secsz=%d", track->num,
              track->filename, track->fad, track->sector_size);
   }
diff --git a/src/guest/holly/holly.c b/src/guest/holly/holly.c
index 321caf0e..e5bc69c1 100644
--- a/src/guest/holly/holly.c
+++ b/src/guest/holly/holly.c
@@ -410,8 +410,7 @@ REG_R32(holly_cb, SB_FFST) {
   return 0;
 }
 
-REG_W32(holly_cb, SB_FFST) {
-}
+REG_W32(holly_cb, SB_FFST) {}
 
 REG_W32(holly_cb, SB_SFRES) {
   /* only reset if the magic value is written */