diff --git a/docs/datasheet/soc.adoc b/docs/datasheet/soc.adoc
index ac2c531a4..642c04609 100644
--- a/docs/datasheet/soc.adoc
+++ b/docs/datasheet/soc.adoc
@@ -196,7 +196,7 @@ The generic type "`suv(x:y)`" is an abbreviation for "`std_ulogic_vector(x downt
 |=======================
 | Name | Type | Default | Description
 4+^| **General**
-| `CLOCK_FREQUENCY`       | natural   | -             | The clock frequency of the processor's `clk_i` input port in Hertz (Hz).
+| `CLOCK_FREQUENCY`       | natural   | 0             | The clock frequency of the processor's `clk_i` input port in Hertz (Hz).
 | `CLOCK_GATING_EN`       | boolean   | false         | Enable clock gating when CPU is in sleep mode (see sections <<_sleep_mode>> and <<_processor_clocking>>).
 | `INT_BOOTLOADER_EN`     | boolean   | false         | Implement the processor-internal <<_bootloader_rom_bootrom>>, pre-initialized with the default <<_bootloader>> image.
 | `HART_ID`               | suv(31:0) | 0x00000000    | The hart thread ID of the CPU (passed to <<_mhartid>> CSR).
diff --git a/rtl/core/neorv32_package.vhd b/rtl/core/neorv32_package.vhd
index 0ffd3cdab..0fca399c8 100644
--- a/rtl/core/neorv32_package.vhd
+++ b/rtl/core/neorv32_package.vhd
@@ -668,7 +668,7 @@ package neorv32_package is
   component neorv32_top
     generic (
       -- General --
-      CLOCK_FREQUENCY       : natural;
+      CLOCK_FREQUENCY       : natural                        := 0;
       CLOCK_GATING_EN       : boolean                        := false;
       HART_ID               : std_ulogic_vector(31 downto 0) := x"00000000";
       JEDEC_ID              : std_ulogic_vector(10 downto 0) := "00000000000";
diff --git a/rtl/core/neorv32_top.vhd b/rtl/core/neorv32_top.vhd
index fc86aa405..9b5e2d932 100644
--- a/rtl/core/neorv32_top.vhd
+++ b/rtl/core/neorv32_top.vhd
@@ -22,7 +22,7 @@ use neorv32.neorv32_package.all;
 entity neorv32_top is
   generic (
     -- General --
-    CLOCK_FREQUENCY       : natural;                                       -- clock frequency of clk_i in Hz
+    CLOCK_FREQUENCY       : natural                        := 0;           -- clock frequency of clk_i in Hz
     CLOCK_GATING_EN       : boolean                        := false;       -- enable clock gating when in sleep mode
     HART_ID               : std_ulogic_vector(31 downto 0) := x"00000000"; -- hardware thread ID
     JEDEC_ID              : std_ulogic_vector(10 downto 0) := "00000000000"; -- JEDEC ID: continuation codes + vendor ID
@@ -374,6 +374,10 @@ begin
     assert not (io_sysinfo_en_c = false) report
       "[NEORV32] SYSINFO module disabled - some parts of the NEORV32 software framework will no longer work!" severity warning;
 
+    -- Clock speed not defined --
+    assert not (CLOCK_FREQUENCY = 0) report
+      "[NEORV32] CLOCK_FREQUENCY must be configured according to the frequency of clk_i port!" severity warning;
+
   end generate; -- /sanity_checks
 
 
diff --git a/sim/simple/ghdl.run.sh b/sim/simple/ghdl.run.sh
index e62787180..0301d2589 100755
--- a/sim/simple/ghdl.run.sh
+++ b/sim/simple/ghdl.run.sh
@@ -4,7 +4,7 @@ set -e
 
 cd $(dirname "$0")
 
-echo "Tip: Compile application with USER_FLAGS+=-DUART[0/1]_SIM_MODE to auto-enable UART[0/1]'s simulation mode (redirect UART output to simulator console)."
+echo "[TIP] Compile application with USER_FLAGS+=-DUART[0/1]_SIM_MODE to enable UART[0/1]'s simulation mode (redirect UART output to simulator console)."
 
 # Prepare simulation output files for UART0 and UART 1
 # - Testbench receiver log file (neorv32.testbench_uart?.out)
diff --git a/sw/common/common.mk b/sw/common/common.mk
index 504473f15..18915fd53 100644
--- a/sw/common/common.mk
+++ b/sw/common/common.mk
@@ -153,7 +153,7 @@ target bootloader | bl_image: CC_OPTS += -Wl,--defsym=MAKE_BOOTLOADER=1 -DMAKE_B
 # -----------------------------------------------------------------------------
 # Compile image generator
 $(IMAGE_GEN): $(NEORV32_EXG_PATH)/image_gen.c
-	@echo Compiling $(IMAGE_GEN)
+	@echo Compiling image generator...
 	@$(CC_HOST) $< -o $(IMAGE_GEN)
 
 # -----------------------------------------------------------------------------
diff --git a/sw/image_gen/image_gen.c b/sw/image_gen/image_gen.c
index d904fd7c1..cf5cf06b3 100644
--- a/sw/image_gen/image_gen.c
+++ b/sw/image_gen/image_gen.c
@@ -83,6 +83,10 @@ int main(int argc, char *argv[]) {
   unsigned int input_words = input_size / 4;
   rewind(input);
 
+  if ((input_size % 4) != 0) {
+    printf("WARNING - image size is not a multiple of 4 bytes.\n");
+  }
+
   // input file empty?
   if(input_size == 0) {
     printf("Input file is empty!");