works for 3 * 5 = 15

mandel.s

@@ -39,14 +39,6 @@ LOG10 = $ded1
 
 .export start
 
-.proc start
-loop:
-    jmp loop
-.endproc
-
-.proc mandelfloat
-.endproc
-
 .macro sext16to32 arg
     .local plus
     .local minus
@@ -208,3 +200,21 @@ loop:
     ; if dist >= 4 break, else continue iterating
 
 .endproc
+
+.proc start
+    ; FR0 = 3
+    ; FR1 = 5
+    lda #3
+    sta FR0
+    lda #5
+    sta FR1
+    lda #0
+    sta FR0 + 1
+    sta FR1 + 1
+
+    jsr imul16
+    ; should have 32-bit 15 in FR2
+
+loop:
+    jmp loop
+.endproc