Changeset 1737 in vbox

Timestamp:

Mar 27, 2007 4:15:38 PM (18 years ago)

Author:

vboxsync

Message:

Fixed a couple off-by-one errors in the CHS handling part
(double-checked with Ralf Brown's interrupt list).

File:

• trunk/src/VBox/Devices/PC/BIOS/rombios.c (modified) (2 diffs)

trunk/src/VBox/Devices/PC/BIOS/rombios.c

@@ -5294 +5294 @@
       count = read_byte(ebda_seg, &EbdaData->ata.hdcount);
 
+#ifndef VBOX
       nlc = nlc - 2; /* 0 based , last sector not used */
+#else /* VBOX */
+      /* Maximum cylinder number is just one less than the number of cylinders. */
+      nlc = nlc - 1; /* 0 based , last sector not used */
+#endif /* VBOX */
       SET_AL(0);
       SET_CH(nlc & 0xff);
@@ -5328 +5333 @@
 
       // Compute sector count seen by int13
+#ifndef VBOX
       lba = (Bit32u)(npc - 1) * (Bit32u)nph * (Bit32u)npspt;
+#else /* VBOX */
+      /* Is it so hard to multiply a couple of counts (without introducing
+       * arbitrary off by one errors)? */
+      lba = (Bit32u)npc * (Bit32u)nph * (Bit32u)npspt;
+#endif /* VBOX */
       CX = lba >> 16;
       DX = lba & 0xffff;