-#define READ_SECTORS 0x02
-#define MBR_SIG_OFFSET 0x1B8
-#define DISK80_SIG_BUFFER 0x2cc
+
+#define READ_SECTORS 0x02 /* int13 AH=0x02 is READ_SECTORS command */
+#define EDD_MBR_SIG_OFFSET 0x1B8 /* offset of signature in the MBR */
+#define EDD_MBR_SIG_BUF 0x290 /* addr in boot params */
+#define EDD_MBR_SIG_MAX 16 /* max number of signatures to store */
+#define EDD_MBR_SIG_NR_BUF 0x1ea /* addr of number of MBR signtaures at EDD_MBR_SIG_BUF
+ in boot_params - treat this as 1 byte */