I don't just mean undocumented op codes, I'm also including documented opcodes but undocumented operand values.
-----Original Message----- From: IBM Mainframe Discussion List <[email protected]> On Behalf Of Paul Gilmartin Sent: Wednesday, June 18, 2025 11:08 AM To: [email protected] Subject: Re: Is there an equivalent of an S-con for a long displacement? On Wed, 18 Jun 2025 15:39:22 +0000, Schmitt, Michael wrote: > ... >Here's I'm thinking of HP-41 Synthetic programming >[https://www.hpmuseum.org/prog/synth41.htm], where you could exploit bugs in >the calculator to construct instructions that the calculator execute, but >would normally not allow you to enter. > ... Reportedly, some such instructions were found during testing or late design review to be defective; removed from the documentation but not from early revisions of the chip. "Use at your own risk!" There's a legend that the IBM 704 STore Zero instruction was unplanned but discovered by customers by "Synthetic programming", and when IBM learned of it they tried to make (support of) it an RPQ. -- gil ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN
