support PCS 1983

src/id/trace.a

@@ -60,11 +60,13 @@ _Inspect1a
          clc
          adc   #$06
          sta   b4bbcompare+1
-         sec
-         sbc   #$02
-         sta   .x3+1
-         sta   .x4+1
-         sta   callrwts+2
+         tax
+         dex
+         stx   .x5+1
+         dex
+         stx   .x3+1
+         stx   .x4+1
+         stx   callrwts+2
          jsr   ProtectedDOS ; check for a specific (encrypted)
                           ; bootloader called "Protected DOS"
          bcs   .notprotdos
@@ -96,7 +98,7 @@ _Inspect1a
          ldy   #$02
          jsr   CompareMemory
          !byte $20,00
-         bcc   +
+         bcc   .x5
 ;
 ; Check for RWTS variant that has extra code before
 ; JSR $B800 e.g. Verb Viper (DLM), Advanced Analogies (Hartley)
@@ -106,7 +108,19 @@ _Inspect1a
          ldy   #$02
          jsr   CompareMemory
          !byte $20,00
-         bcc   +
+         bcc   .x5
+         jmp   UseUniversal ; give up tracing; this RWTS is unsupported
+;
+; Check for RWTS variant that uses non-standard address for slot
+; LDX $1FE8 e.g. Pinball Construction Set (1983)
+; we don't like that one
+;
+.x5      lda   #$FF       ; check for "LDX $1FE8" at $BE43
+         ldx   #$43
+         ldy   #$03
+         jsr   CompareMemory
+         !byte $AE,$E8,$1F
+         bcs   +
          jmp   UseUniversal ; give up tracing; this RWTS is unsupported
 +        jmp   ADStyle    ; use this RWTS to read the disk