diff --git a/src/arch/i386/prefix/romprefix.S b/src/arch/i386/prefix/romprefix.S
index 091673d3..e061932d 100644
--- a/src/arch/i386/prefix/romprefix.S
+++ b/src/arch/i386/prefix/romprefix.S
@@ -25,12 +25,8 @@ FILE_LICENCE ( GPL2_OR_LATER )
 	( PMM_HANDLE_BASE | 0x00002000 )
 #define PCI_FUNC_MASK 0x07
 
-/* ROM banner timeout.  Based on the configurable BANNER_TIMEOUT in
- * config.h, but converted to a number of (18Hz) timer ticks, and
- * doubled to allow for BIOSes that switch video modes immediately
- * beforehand, so rendering the message almost invisible to the user.
- */
-#define ROM_BANNER_TIMEOUT ( 2 * ( 18 * BANNER_TIMEOUT ) / 10 )
+/* ROM banner timeout, converted to a number of (18Hz) timer ticks. */
+#define ROM_BANNER_TIMEOUT_TICKS ( ( 18 * ROM_BANNER_TIMEOUT ) / 10 )
 
 /* Allow payload to be excluded from ROM size
  */
@@ -791,7 +787,7 @@ wait_for_key:
 	int	$0x16
 	jmp	1b
 2:	/* Wait for a key press */
-	movw	$ROM_BANNER_TIMEOUT, %cx
+	movw	$ROM_BANNER_TIMEOUT_TICKS, %cx
 3:	decw	%cx
 	js	99f		/* Exit with ZF clear */
 	/* Wait for timer tick to be updated */
diff --git a/src/config/general.h b/src/config/general.h
index a714a0af..589798fb 100644
--- a/src/config/general.h
+++ b/src/config/general.h
@@ -28,11 +28,22 @@ FILE_LICENCE ( GPL2_OR_LATER );
 #define PRODUCT_SHORT_NAME "iPXE"
 
 /*
- * Timer configuration
+ * Banner timeout configuration
  *
+ * This controls the timeout for the "Press Ctrl-B for the iPXE
+ * command line" banner displayed when iPXE starts up.  The value is
+ * specified in tenths of a second for which the banner should appear.
+ * A value of 0 disables the banner.
+ *
+ * ROM_BANNER_TIMEOUT controls the "Press Ctrl-B to configure iPXE"
+ * banner displayed only by ROM builds of iPXE during POST.  This
+ * defaults to being twice the length of BANNER_TIMEOUT, to allow for
+ * BIOSes that switch video modes immediately before calling the
+ * initialisation vector, thus rendering the banner almost invisible
+ * to the user.
  */
-#define BANNER_TIMEOUT	20	/* Tenths of a second for which the shell
-				   banner should appear */
+#define BANNER_TIMEOUT		20
+#define ROM_BANNER_TIMEOUT	( 2 * BANNER_TIMEOUT )
 
 /*
  * Network protocols