diff --git a/ubb-patgen/README b/ubb-patgen/README
index a250030..82fdada 100644
--- a/ubb-patgen/README
+++ b/ubb-patgen/README
@@ -63,10 +63,6 @@ bus clk = 100.962 kHz (+0.96%)
 
 This warning can be suppressed with the option -q.
 
-The option -F works like -f but also allows frequencies that may
-exceed the hardware's capabilities. As a consequence, the MMC
-controller may hang.
-
 The frequency can also be specified as the cycle time with the
 option -i:
 
@@ -75,6 +71,10 @@ option -i:
 The meaning of an appended + or - changes here, e.g., 10us+
 selects a slower clock (producing an interval of at least 10 us).
 
+The options -F and -I work like -f and -i but also allows
+frequencies that may exceed the hardware's capabilities. As a
+consequence, the MMC controller may hang.
+
 
 Clock output
 ------------
diff --git a/ubb-patgen/ubb-patgen.c b/ubb-patgen/ubb-patgen.c
index 84206f6..2a07eb1 100644
--- a/ubb-patgen/ubb-patgen.c
+++ b/ubb-patgen/ubb-patgen.c
@@ -691,9 +691,9 @@ static void usage(const char *name)
 {
         fprintf(stderr,
 "usage: %s\n"
-"       %s [-q] (-f|-F) freq_hz|-i interval_s\n"
-"       %s [-q] [(-f|-F) freq_hz|-i interval_s] -c [active_s]\n"
-"       %s [-q] [(-f|-F) freq_hz|-i interval_s]\n"
+"       %s [-q] (-f|-F) freq_hz|(-i|-I) interval_s\n"
+"       %s [-q] [(-f|-F) freq_hz|(-i|-I) interval_s] -c [active_s]\n"
+"       %s [-q] [(-f|-F) freq_hz|(-i|-I) interval_s]\n"
 "         [-C|-t 0|1... [-d debounce_s]] [-w wait_s] [-m mask] [-p]\n"
 "         file|pattern\n\n"
 "  -c          output bus clock on CLK without sending a pattern\n"
@@ -703,6 +703,7 @@ static void usage(const char *name)
 "  -F freq_hz  like -f, but also allow \"overclocking\"\n"
 "  -i inter_s  set bus clock such that one cycle equals the specified "
   "interval\n"
+"  -I inter_s  like -i, but also allow \"overclocking\"\n"
 "  -m mask     use only the DATx lines specified in the mask (default: 0xf)\n"
 "  -p          force interpretation of argument as pattern (and not file)\n"
 "  -q          quiet. Don't pretty-print frequencies; don't report clock\n"
@@ -749,7 +750,7 @@ int main(int argc, char **argv)
 	unsigned long tmp;
 	const char *p;
 
-	while ((c = getopt(argc, argv, "cCd:f:F:i:m:pqt:w:")) != EOF)
+	while ((c = getopt(argc, argv, "cCd:f:F:i:I:m:pqt:w:")) != EOF)
 		switch (c) {
 		case 'c':
 			clk_only = 1;
@@ -772,6 +773,9 @@ int main(int argc, char **argv)
 			if (!frequency(optarg, &bus_hz, &bus_rel))
 				usage(*argv);
 			break;
+		case 'I':
+			all = 1;
+			/* fall through */
 		case 'i':
 			if (!interval(optarg, &bus_hz, &bus_rel))
 				usage(*argv);