Changeset 47036 in vbox for trunk/src/VBox/Devices/PC/BIOS

Timestamp:

Jul 8, 2013 12:26:47 PM (12 years ago)

Author:

vboxsync

Message:

BIOS,DevFdc,DrvBlock: The floppy controller should query the block/host driver for the drive type, or it'll all go real bad if the guest code trusts CMOS/BIOS drive info. Changed the block driver to automatically upgrade the drive type (for fdc and bios/cmos setup only) if the image is larger than the configured drive capacity. Introduced two fake drive types with max capacities, 15.6 MB and 63.5 MB, the first is the max that INT13 can officially access, the second is reinterpreting CL as holding an 8-bit wide sector number and no cylinder bits (which actually seems to be how real bioses work with floppies).

File:

• trunk/src/VBox/Devices/PC/BIOS/floppy.c (modified) (4 diffs)

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

@@ -392 +392 @@
         retval = 1;
     }
+    else if ( drive_type == 14 || drive_type == 15 ) {
+        // 15.6 MB 3.5" (fake) || 63.5 MB 3.5" (fake) - report same as 2.88 MB.
+        config_data = 0xCC; // 1100 1100
+        media_state = 0xD7; // 1101 0111
+        retval = 1;
+    }
     else {
         // not recognized
@@ -1026 +1032 @@
         SET_AL(0);
         SET_DL(num_floppies);
+        SET_DH(1);      // max head #
         
         switch (drive_type) {
@@ -1035 +1042 @@
         case 1: // 360KB, 5.25"
             CX = 0x2709;    // 40 tracks, 9 sectors
-            SET_DH(1);      // max head #
             break;
         
         case 2: // 1.2MB, 5.25"
             CX = 0x4f0f;    // 80 tracks, 15 sectors
-            SET_DH(1);      // max head #
             break;
         
         case 3: // 720KB, 3.5"
             CX = 0x4f09;    // 80 tracks, 9 sectors
-            SET_DH(1);      // max head #
             break;
         
         case 4: // 1.44MB, 3.5"
             CX = 0x4f12;    // 80 tracks, 18 sectors
-            SET_DH(1);      // max head #
             break;
         
         case 5: // 2.88MB, 3.5"
             CX = 0x4f24;    // 80 tracks, 36 sectors
-            SET_DH(1);      // max head #
             break;
         
@@ -1070 +1072 @@
         case 8: // 320k, 5.25"
             CX = 0x2708;    // 40 tracks, 8 sectors
-            SET_DH(1);      // max head #
-            break;
-        
+            break;
+        
+        case 14: // 15.6 MB 3.5" (fake)
+            CX = 0xfe3f;    // 255 tracks, 63 sectors
+            break;
+
+        case 15: // 63.5 MB 3.5" (fake)
+            CX = 0xfeff;    // 255 tracks, 255 sectors - This works because the cylinder
+            break;          // and sectors limits/encoding aren't checked by the BIOS
+                            // due to copy protection schemes and such stuff.
+
         default: // ?
             BX_PANIC("%s: bad floppy type\n", __func__);