Changeset 231 in xtideuniversalbios for trunk/XTIDE_Universal_BIOS

Timestamp:

Jan 31, 2012, 5:46:56 PM (13 years ago)

Author:

krille_n_@…

google:author:

krille_n_@hotmail.com

Message:

Changes:

• Additional tweaks to AccessDPT_ShiftPCHinAXBLtoLCH in AccessDPT.asm

File:

• trunk/XTIDE_Universal_BIOS/Src/VariablesAndDPTs/AccessDPT.asm (modified) (1 diff)

trunk/XTIDE_Universal_BIOS/Src/VariablesAndDPTs/AccessDPT.asm

@@ -90 +90 @@
 .ShiftLoop:
     cmp     ax, MAX_LCHS_CYLINDERS      ; Need to shift?
-    jbe     SHORT .LimitHeadsTo255      ;  If not, return
+    jbe     SHORT .Return               ;  If not, return
     inc     cx                          ; Increment shift count
     shr     ax, 1                       ; Halve cylinders
     shl     bl, 1                       ; Double heads
-    jnz     SHORT .ShiftLoop
-.LimitHeadsTo255:                       ; DOS does not support drives with 256 heads
-    cmp     bl, cl                      ; Set CF if BL is zero
-    sbb     bl, ch                      ; If BL=0 then BL=255
+    jnz     SHORT .ShiftLoop            ; Falls through only on the last (4th) iteration and only if BL was 16 on entry
+    dec     bl                          ; DOS doesn't support drives with 256 heads so we limit heads to 255
+    ; We can save a byte here by using DEC BX if we don't care about BH
+.Return:
     ret