diff --git a/fuzzers/030-iob18/generate.py b/fuzzers/030-iob18/generate.py
index c1517389..2dd7958c 100644
--- a/fuzzers/030-iob18/generate.py
+++ b/fuzzers/030-iob18/generate.py
@@ -19,11 +19,7 @@ import csv
 from iostandards import *
 
 def bitfilter(frame, word):
-    # the fuzzers seem to find bits in frame 24 which seems
-    # to be used by other tile types
-    if frame < 30:
-         return False
-    return True
+    return 38 <= frame
 
 def mk_drive_opt(iostandard, drive):
     if drive is None:
diff --git a/fuzzers/036-iob18-ologic/generate.py b/fuzzers/036-iob18-ologic/generate.py
index 35b7d445..fca2ee2f 100644
--- a/fuzzers/036-iob18-ologic/generate.py
+++ b/fuzzers/036-iob18-ologic/generate.py
@@ -18,14 +18,7 @@ DEBUG_FUZZER = False
 
 
 def bitfilter(frame, word):
-    # TODO: do we need this here?
-    # this frame number limit does not seem 
-    # to apply to 1.8V high speed banks
-    #if frame < 30 or frame > 37:
-    #    return False
-
-    return True
-
+    return 30 <= frame and frame <= 33
 
 def handle_data_width(segmk, d):
     if 'DATA_WIDTH' not in d: