1581 ROM Versions:

   Revision 1 ("old"): Chip #318045-01 (also 312558-01), used until 1992?
   Revision 2 ("new"): Chip #318045-02, used from 1992? on

   AAY1581 contains a disassembly of the new version, but differences
   are also stated. They are at:

  +-------------+-----------------------------------------------------------
  | $AF8C       | Ignore false ROM checksum
  | $C160-$C162 | Apply patch at $C5AF in newer version
  | $C5AF-$C5B2 | Disable interrupts during Job execution
  +-------------+-----------------------------------------------------------