OSI: Fix RAM top detection. Real hardware does not read 0xff when

there's no RAM, but it returns the MSB of the address. Test RAM with a value that is not equal to the MSB of the address.
davidgiven · Jan 16, 2025 · 5a0272a · 5a0272a
1 parent b3de3aa
commit 5a0272a
Showing 1 changed file with 2 additions and 0 deletions.
diff --git a/src/arch/osi/osi.S b/src/arch/osi/osi.S
@@ -163,10 +163,12 @@ init:
         lda ptr+1
         cmp #$c0
         zbreakif_eq
+        lda #$3f
         sta (ptr),y
         cmp (ptr),y
     zuntil_ne
 
+    lda ptr+1
     sec
     sbc #PAGES_PER_TRACK
     sta ptrkbuf                     ; put track buffer at ramtop