Changeset 543 in xtideuniversalbios for trunk/XTIDE_Universal_BIOS/Src/VariablesAndDPTs/CreateDPT.asm

Timestamp:

Apr 16, 2013, 11:41:49 AM (12 years ago)

Author:

aitotat@…

google:author:

aitotat@gmail.com

Message:

Changes to XTIDE Universal BIOS:

• Compatible DPTs can no longer have more than 1024 cylinders.

File:

• trunk/XTIDE_Universal_BIOS/Src/VariablesAndDPTs/CreateDPT.asm (modified) (2 diffs)

trunk/XTIDE_Universal_BIOS/Src/VariablesAndDPTs/CreateDPT.asm

@@ -144 +144 @@
     xchg    cx, ax
     div     cx                              ; AX = new P-Cylinders
+
+    ; We could remove wPchsCylinders from DPT if we calculate it on AH=48h
+    ; but that would require extra code so we save ROM space instead.
     mov     [di+DPT.wPchsCylinders], ax
 
-    ; Store CHS sector count as total sector count
+    ; Store CHS sector count as total sector count. We must not use
+    ; LBA sector count if it is 15,482,880 or less.
     mul     cx
     xor     bx, bx
-    xor     cx, cx                          ; Clear LBA48 flag
-    jmp     SHORT .StoreTotalSectorsFromBXDXAXandLBA48flagFromCL
+    jmp     SHORT .StoreTotalSectorsFromBXDXAX
     ; Fall to .StoreNumberOfLbaSectors
 
@@ -167 +170 @@
     ; Store LBA 28/48 total sector count
     call    AtaGeometry_GetLbaSectorCountToBXDXAXfromAtaInfoInESSI
-.StoreTotalSectorsFromBXDXAXandLBA48flagFromCL:
-    or      [di+DPT.bFlagsLow], cl
+    or      [di+DPT.bFlagsLow], cl      ; LBA48 flag
+.StoreTotalSectorsFromBXDXAX:
     mov     [di+DPT.twLbaSectors], ax
     mov     [di+DPT.twLbaSectors+2], dx