diff --git a/src/mame/drivers/x1.cpp b/src/mame/drivers/x1.cpp
index 53c11e9319c..cee20b3fbea 100644
--- a/src/mame/drivers/x1.cpp
+++ b/src/mame/drivers/x1.cpp
@@ -57,12 +57,13 @@
       Any i/o read disables this extended bitmap ram.
     - I/O port $700 bit 7 of X1 Turbo is a sound (dip-)switch / jumper setting. I don't know yet what is for,
       but King's Knight needs it to be active otherwise it refuses to boot.
-    - ROM format is:
-      0x00 ROM id (must be 0x01)
-      0x01 - 0x0e ROM header
-      0xff16 - 0xff17 start-up vector
-      In theory, you can convert your tape / floppy games into ROM format easily, provided that you know what's the pinout of the
-      cartridge slot and it doesn't exceed 64k (0x10000) of size.
+    - ROM format header:
+      [0x00] ROM identifier, must be 0x01 / SOH
+      [0x01 to 0x0d] ROM header, i.e. title for the loader
+      [0x12 -  0x13] initial copy size
+      [0x14 -  0x15] destination address start address
+      [0x16 to 0x17] start boot jump vector 
+      [0x1d to 0x1f] start boot data vector
     - Gruppe: shows a random bitmap graphic then returns "program load error" ... it wants that the floppy has write protection enabled (!) (btanb)
     - Maidum: you need to load BOTH disk with write protection disabled, otherwise it refuses to run. (btanb)
     - Marvelous: needs write protection disabled (btanb)